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OpenCloudOS-Kernel/drivers/spi/spi-bcm2835.c

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Driver for Broadcom BCM2835 SPI Controllers
*
* Copyright (C) 2012 Chris Boot
* Copyright (C) 2013 Stephen Warren
* Copyright (C) 2015 Martin Sperl
*
* This driver is inspired by:
* spi-ath79.c, Copyright (C) 2009-2011 Gabor Juhos <juhosg@openwrt.org>
* spi-atmel.c, Copyright (C) 2006 Atmel Corporation
*/
#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/debugfs.h>
#include <linux/delay.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>
#include <linux/err.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_device.h>
#include <linux/of_gpio.h>
#include <linux/of_irq.h>
#include <linux/spi/spi.h>
/* SPI register offsets */
#define BCM2835_SPI_CS 0x00
#define BCM2835_SPI_FIFO 0x04
#define BCM2835_SPI_CLK 0x08
#define BCM2835_SPI_DLEN 0x0c
#define BCM2835_SPI_LTOH 0x10
#define BCM2835_SPI_DC 0x14
/* Bitfields in CS */
#define BCM2835_SPI_CS_LEN_LONG 0x02000000
#define BCM2835_SPI_CS_DMA_LEN 0x01000000
#define BCM2835_SPI_CS_CSPOL2 0x00800000
#define BCM2835_SPI_CS_CSPOL1 0x00400000
#define BCM2835_SPI_CS_CSPOL0 0x00200000
#define BCM2835_SPI_CS_RXF 0x00100000
#define BCM2835_SPI_CS_RXR 0x00080000
#define BCM2835_SPI_CS_TXD 0x00040000
#define BCM2835_SPI_CS_RXD 0x00020000
#define BCM2835_SPI_CS_DONE 0x00010000
#define BCM2835_SPI_CS_LEN 0x00002000
#define BCM2835_SPI_CS_REN 0x00001000
#define BCM2835_SPI_CS_ADCS 0x00000800
#define BCM2835_SPI_CS_INTR 0x00000400
#define BCM2835_SPI_CS_INTD 0x00000200
#define BCM2835_SPI_CS_DMAEN 0x00000100
#define BCM2835_SPI_CS_TA 0x00000080
#define BCM2835_SPI_CS_CSPOL 0x00000040
#define BCM2835_SPI_CS_CLEAR_RX 0x00000020
#define BCM2835_SPI_CS_CLEAR_TX 0x00000010
#define BCM2835_SPI_CS_CPOL 0x00000008
#define BCM2835_SPI_CS_CPHA 0x00000004
#define BCM2835_SPI_CS_CS_10 0x00000002
#define BCM2835_SPI_CS_CS_01 0x00000001
#define BCM2835_SPI_FIFO_SIZE 64
#define BCM2835_SPI_FIFO_SIZE_3_4 48
#define BCM2835_SPI_DMA_MIN_LENGTH 96
#define BCM2835_SPI_MODE_BITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH \
| SPI_NO_CS | SPI_3WIRE)
#define DRV_NAME "spi-bcm2835"
/* define polling limits */
unsigned int polling_limit_us = 30;
module_param(polling_limit_us, uint, 0664);
MODULE_PARM_DESC(polling_limit_us,
"time in us to run a transfer in polling mode\n");
/**
* struct bcm2835_spi - BCM2835 SPI controller
* @regs: base address of register map
* @clk: core clock, divided to calculate serial clock
* @irq: interrupt, signals TX FIFO empty or RX FIFO ¾ full
* @tfr: SPI transfer currently processed
* @tx_buf: pointer whence next transmitted byte is read
* @rx_buf: pointer where next received byte is written
* @tx_len: remaining bytes to transmit
* @rx_len: remaining bytes to receive
* @tx_prologue: bytes transmitted without DMA if first TX sglist entry's
* length is not a multiple of 4 (to overcome hardware limitation)
* @rx_prologue: bytes received without DMA if first RX sglist entry's
* length is not a multiple of 4 (to overcome hardware limitation)
* @tx_spillover: whether @tx_prologue spills over to second TX sglist entry
* @dma_pending: whether a DMA transfer is in progress
* @debugfs_dir: the debugfs directory - neede to remove debugfs when
* unloading the module
* @count_transfer_polling: count of how often polling mode is used
* @count_transfer_irq: count of how often interrupt mode is used
* @count_transfer_irq_after_polling: count of how often we fall back to
* interrupt mode after starting in polling mode.
* These are counted as well in @count_transfer_polling and
* @count_transfer_irq
* @count_transfer_dma: count how often dma mode is used
*/
struct bcm2835_spi {
void __iomem *regs;
struct clk *clk;
int irq;
struct spi_transfer *tfr;
const u8 *tx_buf;
u8 *rx_buf;
int tx_len;
int rx_len;
int tx_prologue;
int rx_prologue;
unsigned int tx_spillover;
unsigned int dma_pending;
struct dentry *debugfs_dir;
u64 count_transfer_polling;
u64 count_transfer_irq;
u64 count_transfer_irq_after_polling;
u64 count_transfer_dma;
};
#if defined(CONFIG_DEBUG_FS)
static void bcm2835_debugfs_create(struct bcm2835_spi *bs,
const char *dname)
{
char name[64];
struct dentry *dir;
/* get full name */
snprintf(name, sizeof(name), "spi-bcm2835-%s", dname);
/* the base directory */
dir = debugfs_create_dir(name, NULL);
bs->debugfs_dir = dir;
/* the counters */
debugfs_create_u64("count_transfer_polling", 0444, dir,
&bs->count_transfer_polling);
debugfs_create_u64("count_transfer_irq", 0444, dir,
&bs->count_transfer_irq);
debugfs_create_u64("count_transfer_irq_after_polling", 0444, dir,
&bs->count_transfer_irq_after_polling);
debugfs_create_u64("count_transfer_dma", 0444, dir,
&bs->count_transfer_dma);
}
static void bcm2835_debugfs_remove(struct bcm2835_spi *bs)
{
debugfs_remove_recursive(bs->debugfs_dir);
bs->debugfs_dir = NULL;
}
#else
static void bcm2835_debugfs_create(struct bcm2835_spi *bs,
const char *dname)
{
}
static void bcm2835_debugfs_remove(struct bcm2835_spi *bs)
{
}
#endif /* CONFIG_DEBUG_FS */
static inline u32 bcm2835_rd(struct bcm2835_spi *bs, unsigned reg)
{
return readl(bs->regs + reg);
}
static inline void bcm2835_wr(struct bcm2835_spi *bs, unsigned reg, u32 val)
{
writel(val, bs->regs + reg);
}
static inline void bcm2835_rd_fifo(struct bcm2835_spi *bs)
{
u8 byte;
while ((bs->rx_len) &&
(bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_RXD)) {
byte = bcm2835_rd(bs, BCM2835_SPI_FIFO);
if (bs->rx_buf)
*bs->rx_buf++ = byte;
bs->rx_len--;
}
}
static inline void bcm2835_wr_fifo(struct bcm2835_spi *bs)
{
u8 byte;
while ((bs->tx_len) &&
(bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_TXD)) {
byte = bs->tx_buf ? *bs->tx_buf++ : 0;
bcm2835_wr(bs, BCM2835_SPI_FIFO, byte);
bs->tx_len--;
}
}
/**
* bcm2835_rd_fifo_count() - blindly read exactly @count bytes from RX FIFO
* @bs: BCM2835 SPI controller
* @count: bytes to read from RX FIFO
*
* The caller must ensure that @bs->rx_len is greater than or equal to @count,
* that the RX FIFO contains at least @count bytes and that the DMA Enable flag
* in the CS register is set (such that a read from the FIFO register receives
* 32-bit instead of just 8-bit). Moreover @bs->rx_buf must not be %NULL.
*/
static inline void bcm2835_rd_fifo_count(struct bcm2835_spi *bs, int count)
{
u32 val;
int len;
bs->rx_len -= count;
while (count > 0) {
val = bcm2835_rd(bs, BCM2835_SPI_FIFO);
len = min(count, 4);
memcpy(bs->rx_buf, &val, len);
bs->rx_buf += len;
count -= 4;
}
}
/**
* bcm2835_wr_fifo_count() - blindly write exactly @count bytes to TX FIFO
* @bs: BCM2835 SPI controller
* @count: bytes to write to TX FIFO
*
* The caller must ensure that @bs->tx_len is greater than or equal to @count,
* that the TX FIFO can accommodate @count bytes and that the DMA Enable flag
* in the CS register is set (such that a write to the FIFO register transmits
* 32-bit instead of just 8-bit).
*/
static inline void bcm2835_wr_fifo_count(struct bcm2835_spi *bs, int count)
{
u32 val;
int len;
bs->tx_len -= count;
while (count > 0) {
if (bs->tx_buf) {
len = min(count, 4);
memcpy(&val, bs->tx_buf, len);
bs->tx_buf += len;
} else {
val = 0;
}
bcm2835_wr(bs, BCM2835_SPI_FIFO, val);
count -= 4;
}
}
/**
* bcm2835_wait_tx_fifo_empty() - busy-wait for TX FIFO to empty
* @bs: BCM2835 SPI controller
*
* The caller must ensure that the RX FIFO can accommodate as many bytes
* as have been written to the TX FIFO: Transmission is halted once the
* RX FIFO is full, causing this function to spin forever.
*/
static inline void bcm2835_wait_tx_fifo_empty(struct bcm2835_spi *bs)
{
while (!(bcm2835_rd(bs, BCM2835_SPI_CS) & BCM2835_SPI_CS_DONE))
cpu_relax();
}
/**
* bcm2835_rd_fifo_blind() - blindly read up to @count bytes from RX FIFO
* @bs: BCM2835 SPI controller
* @count: bytes available for reading in RX FIFO
*/
static inline void bcm2835_rd_fifo_blind(struct bcm2835_spi *bs, int count)
{
u8 val;
count = min(count, bs->rx_len);
bs->rx_len -= count;
while (count) {
val = bcm2835_rd(bs, BCM2835_SPI_FIFO);
if (bs->rx_buf)
*bs->rx_buf++ = val;
count--;
}
}
/**
* bcm2835_wr_fifo_blind() - blindly write up to @count bytes to TX FIFO
* @bs: BCM2835 SPI controller
* @count: bytes available for writing in TX FIFO
*/
static inline void bcm2835_wr_fifo_blind(struct bcm2835_spi *bs, int count)
{
u8 val;
count = min(count, bs->tx_len);
bs->tx_len -= count;
while (count) {
val = bs->tx_buf ? *bs->tx_buf++ : 0;
bcm2835_wr(bs, BCM2835_SPI_FIFO, val);
count--;
}
}
static void bcm2835_spi_reset_hw(struct spi_controller *ctlr)
{
struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);
/* Disable SPI interrupts and transfer */
cs &= ~(BCM2835_SPI_CS_INTR |
BCM2835_SPI_CS_INTD |
BCM2835_SPI_CS_DMAEN |
BCM2835_SPI_CS_TA);
/* and reset RX/TX FIFOS */
cs |= BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX;
/* and reset the SPI_HW */
bcm2835_wr(bs, BCM2835_SPI_CS, cs);
/* as well as DLEN */
bcm2835_wr(bs, BCM2835_SPI_DLEN, 0);
}
static irqreturn_t bcm2835_spi_interrupt(int irq, void *dev_id)
{
struct spi_controller *ctlr = dev_id;
struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);
/*
* An interrupt is signaled either if DONE is set (TX FIFO empty)
* or if RXR is set (RX FIFO >= ¾ full).
*/
if (cs & BCM2835_SPI_CS_RXF)
bcm2835_rd_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE);
else if (cs & BCM2835_SPI_CS_RXR)
bcm2835_rd_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE_3_4);
if (bs->tx_len && cs & BCM2835_SPI_CS_DONE)
bcm2835_wr_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE);
/* Read as many bytes as possible from FIFO */
bcm2835_rd_fifo(bs);
/* Write as many bytes as possible to FIFO */
bcm2835_wr_fifo(bs);
if (!bs->rx_len) {
/* Transfer complete - reset SPI HW */
bcm2835_spi_reset_hw(ctlr);
/* wake up the framework */
complete(&ctlr->xfer_completion);
}
return IRQ_HANDLED;
}
static int bcm2835_spi_transfer_one_irq(struct spi_controller *ctlr,
struct spi_device *spi,
struct spi_transfer *tfr,
u32 cs, bool fifo_empty)
{
struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
/* update usage statistics */
bs->count_transfer_irq++;
/*
* Enable HW block, but with interrupts still disabled.
* Otherwise the empty TX FIFO would immediately trigger an interrupt.
*/
bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA);
/* fill TX FIFO as much as possible */
if (fifo_empty)
bcm2835_wr_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE);
bcm2835_wr_fifo(bs);
/* enable interrupts */
cs |= BCM2835_SPI_CS_INTR | BCM2835_SPI_CS_INTD | BCM2835_SPI_CS_TA;
bcm2835_wr(bs, BCM2835_SPI_CS, cs);
/* signal that we need to wait for completion */
return 1;
}
/**
* bcm2835_spi_transfer_prologue() - transfer first few bytes without DMA
* @ctlr: SPI master controller
* @tfr: SPI transfer
* @bs: BCM2835 SPI controller
* @cs: CS register
*
* A limitation in DMA mode is that the FIFO must be accessed in 4 byte chunks.
* Only the final write access is permitted to transmit less than 4 bytes, the
* SPI controller deduces its intended size from the DLEN register.
*
* If a TX or RX sglist contains multiple entries, one per page, and the first
* entry starts in the middle of a page, that first entry's length may not be
* a multiple of 4. Subsequent entries are fine because they span an entire
* page, hence do have a length that's a multiple of 4.
*
* This cannot happen with kmalloc'ed buffers (which is what most clients use)
* because they are contiguous in physical memory and therefore not split on
* page boundaries by spi_map_buf(). But it *can* happen with vmalloc'ed
* buffers.
*
* The DMA engine is incapable of combining sglist entries into a continuous
* stream of 4 byte chunks, it treats every entry separately: A TX entry is
* rounded up a to a multiple of 4 bytes by transmitting surplus bytes, an RX
* entry is rounded up by throwing away received bytes.
*
* Overcome this limitation by transferring the first few bytes without DMA:
* E.g. if the first TX sglist entry's length is 23 and the first RX's is 42,
* write 3 bytes to the TX FIFO but read only 2 bytes from the RX FIFO.
* The residue of 1 byte in the RX FIFO is picked up by DMA. Together with
* the rest of the first RX sglist entry it makes up a multiple of 4 bytes.
*
* Should the RX prologue be larger, say, 3 vis-à-vis a TX prologue of 1,
* write 1 + 4 = 5 bytes to the TX FIFO and read 3 bytes from the RX FIFO.
* Caution, the additional 4 bytes spill over to the second TX sglist entry
* if the length of the first is *exactly* 1.
*
* At most 6 bytes are written and at most 3 bytes read. Do we know the
* transfer has this many bytes? Yes, see BCM2835_SPI_DMA_MIN_LENGTH.
*
* The FIFO is normally accessed with 8-bit width by the CPU and 32-bit width
* by the DMA engine. Toggling the DMA Enable flag in the CS register switches
* the width but also garbles the FIFO's contents. The prologue must therefore
* be transmitted in 32-bit width to ensure that the following DMA transfer can
* pick up the residue in the RX FIFO in ungarbled form.
*/
static void bcm2835_spi_transfer_prologue(struct spi_controller *ctlr,
struct spi_transfer *tfr,
struct bcm2835_spi *bs,
u32 cs)
{
int tx_remaining;
bs->tfr = tfr;
bs->tx_prologue = 0;
bs->rx_prologue = 0;
bs->tx_spillover = false;
if (!sg_is_last(&tfr->tx_sg.sgl[0]))
bs->tx_prologue = sg_dma_len(&tfr->tx_sg.sgl[0]) & 3;
if (!sg_is_last(&tfr->rx_sg.sgl[0])) {
bs->rx_prologue = sg_dma_len(&tfr->rx_sg.sgl[0]) & 3;
if (bs->rx_prologue > bs->tx_prologue) {
if (sg_is_last(&tfr->tx_sg.sgl[0])) {
bs->tx_prologue = bs->rx_prologue;
} else {
bs->tx_prologue += 4;
bs->tx_spillover =
!(sg_dma_len(&tfr->tx_sg.sgl[0]) & ~3);
}
}
}
/* rx_prologue > 0 implies tx_prologue > 0, so check only the latter */
if (!bs->tx_prologue)
return;
/* Write and read RX prologue. Adjust first entry in RX sglist. */
if (bs->rx_prologue) {
bcm2835_wr(bs, BCM2835_SPI_DLEN, bs->rx_prologue);
bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA
| BCM2835_SPI_CS_DMAEN);
bcm2835_wr_fifo_count(bs, bs->rx_prologue);
bcm2835_wait_tx_fifo_empty(bs);
bcm2835_rd_fifo_count(bs, bs->rx_prologue);
bcm2835_spi_reset_hw(ctlr);
dma_sync_single_for_device(ctlr->dma_rx->device->dev,
sg_dma_address(&tfr->rx_sg.sgl[0]),
bs->rx_prologue, DMA_FROM_DEVICE);
sg_dma_address(&tfr->rx_sg.sgl[0]) += bs->rx_prologue;
sg_dma_len(&tfr->rx_sg.sgl[0]) -= bs->rx_prologue;
}
/*
* Write remaining TX prologue. Adjust first entry in TX sglist.
* Also adjust second entry if prologue spills over to it.
*/
tx_remaining = bs->tx_prologue - bs->rx_prologue;
if (tx_remaining) {
bcm2835_wr(bs, BCM2835_SPI_DLEN, tx_remaining);
bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA
| BCM2835_SPI_CS_DMAEN);
bcm2835_wr_fifo_count(bs, tx_remaining);
bcm2835_wait_tx_fifo_empty(bs);
bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_CLEAR_TX);
}
if (likely(!bs->tx_spillover)) {
sg_dma_address(&tfr->tx_sg.sgl[0]) += bs->tx_prologue;
sg_dma_len(&tfr->tx_sg.sgl[0]) -= bs->tx_prologue;
} else {
sg_dma_len(&tfr->tx_sg.sgl[0]) = 0;
sg_dma_address(&tfr->tx_sg.sgl[1]) += 4;
sg_dma_len(&tfr->tx_sg.sgl[1]) -= 4;
}
}
/**
* bcm2835_spi_undo_prologue() - reconstruct original sglist state
* @bs: BCM2835 SPI controller
*
* Undo changes which were made to an SPI transfer's sglist when transmitting
* the prologue. This is necessary to ensure the same memory ranges are
* unmapped that were originally mapped.
*/
static void bcm2835_spi_undo_prologue(struct bcm2835_spi *bs)
{
struct spi_transfer *tfr = bs->tfr;
if (!bs->tx_prologue)
return;
if (bs->rx_prologue) {
sg_dma_address(&tfr->rx_sg.sgl[0]) -= bs->rx_prologue;
sg_dma_len(&tfr->rx_sg.sgl[0]) += bs->rx_prologue;
}
if (likely(!bs->tx_spillover)) {
sg_dma_address(&tfr->tx_sg.sgl[0]) -= bs->tx_prologue;
sg_dma_len(&tfr->tx_sg.sgl[0]) += bs->tx_prologue;
} else {
sg_dma_len(&tfr->tx_sg.sgl[0]) = bs->tx_prologue - 4;
sg_dma_address(&tfr->tx_sg.sgl[1]) -= 4;
sg_dma_len(&tfr->tx_sg.sgl[1]) += 4;
}
}
static void bcm2835_spi_dma_done(void *data)
{
struct spi_controller *ctlr = data;
struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
/* reset fifo and HW */
bcm2835_spi_reset_hw(ctlr);
/* and terminate tx-dma as we do not have an irq for it
* because when the rx dma will terminate and this callback
* is called the tx-dma must have finished - can't get to this
* situation otherwise...
*/
if (cmpxchg(&bs->dma_pending, true, false)) {
dmaengine_terminate_async(ctlr->dma_tx);
bcm2835_spi_undo_prologue(bs);
}
/* and mark as completed */;
complete(&ctlr->xfer_completion);
}
static int bcm2835_spi_prepare_sg(struct spi_controller *ctlr,
struct spi_transfer *tfr,
bool is_tx)
{
struct dma_chan *chan;
struct scatterlist *sgl;
unsigned int nents;
enum dma_transfer_direction dir;
unsigned long flags;
struct dma_async_tx_descriptor *desc;
dma_cookie_t cookie;
if (is_tx) {
dir = DMA_MEM_TO_DEV;
chan = ctlr->dma_tx;
nents = tfr->tx_sg.nents;
sgl = tfr->tx_sg.sgl;
flags = 0 /* no tx interrupt */;
} else {
dir = DMA_DEV_TO_MEM;
chan = ctlr->dma_rx;
nents = tfr->rx_sg.nents;
sgl = tfr->rx_sg.sgl;
flags = DMA_PREP_INTERRUPT;
}
/* prepare the channel */
desc = dmaengine_prep_slave_sg(chan, sgl, nents, dir, flags);
if (!desc)
return -EINVAL;
/* set callback for rx */
if (!is_tx) {
desc->callback = bcm2835_spi_dma_done;
desc->callback_param = ctlr;
}
/* submit it to DMA-engine */
cookie = dmaengine_submit(desc);
return dma_submit_error(cookie);
}
static int bcm2835_spi_transfer_one_dma(struct spi_controller *ctlr,
struct spi_device *spi,
struct spi_transfer *tfr,
u32 cs)
{
struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
int ret;
/* update usage statistics */
bs->count_transfer_dma++;
/*
* Transfer first few bytes without DMA if length of first TX or RX
* sglist entry is not a multiple of 4 bytes (hardware limitation).
*/
bcm2835_spi_transfer_prologue(ctlr, tfr, bs, cs);
/* setup tx-DMA */
ret = bcm2835_spi_prepare_sg(ctlr, tfr, true);
if (ret)
goto err_reset_hw;
/* start TX early */
dma_async_issue_pending(ctlr->dma_tx);
/* mark as dma pending */
bs->dma_pending = 1;
/* set the DMA length */
bcm2835_wr(bs, BCM2835_SPI_DLEN, bs->tx_len);
/* start the HW */
bcm2835_wr(bs, BCM2835_SPI_CS,
cs | BCM2835_SPI_CS_TA | BCM2835_SPI_CS_DMAEN);
/* setup rx-DMA late - to run transfers while
* mapping of the rx buffers still takes place
* this saves 10us or more.
*/
ret = bcm2835_spi_prepare_sg(ctlr, tfr, false);
if (ret) {
/* need to reset on errors */
dmaengine_terminate_sync(ctlr->dma_tx);
bs->dma_pending = false;
goto err_reset_hw;
}
/* start rx dma late */
dma_async_issue_pending(ctlr->dma_rx);
/* wait for wakeup in framework */
return 1;
err_reset_hw:
bcm2835_spi_reset_hw(ctlr);
bcm2835_spi_undo_prologue(bs);
return ret;
}
static bool bcm2835_spi_can_dma(struct spi_controller *ctlr,
struct spi_device *spi,
struct spi_transfer *tfr)
{
/* we start DMA efforts only on bigger transfers */
if (tfr->len < BCM2835_SPI_DMA_MIN_LENGTH)
return false;
/* return OK */
return true;
}
static void bcm2835_dma_release(struct spi_controller *ctlr)
{
if (ctlr->dma_tx) {
dmaengine_terminate_sync(ctlr->dma_tx);
dma_release_channel(ctlr->dma_tx);
ctlr->dma_tx = NULL;
}
if (ctlr->dma_rx) {
dmaengine_terminate_sync(ctlr->dma_rx);
dma_release_channel(ctlr->dma_rx);
ctlr->dma_rx = NULL;
}
}
static void bcm2835_dma_init(struct spi_controller *ctlr, struct device *dev)
{
struct dma_slave_config slave_config;
const __be32 *addr;
dma_addr_t dma_reg_base;
int ret;
/* base address in dma-space */
addr = of_get_address(ctlr->dev.of_node, 0, NULL, NULL);
if (!addr) {
dev_err(dev, "could not get DMA-register address - not using dma mode\n");
goto err;
}
dma_reg_base = be32_to_cpup(addr);
/* get tx/rx dma */
ctlr->dma_tx = dma_request_slave_channel(dev, "tx");
if (!ctlr->dma_tx) {
dev_err(dev, "no tx-dma configuration found - not using dma mode\n");
goto err;
}
ctlr->dma_rx = dma_request_slave_channel(dev, "rx");
if (!ctlr->dma_rx) {
dev_err(dev, "no rx-dma configuration found - not using dma mode\n");
goto err_release;
}
/* configure DMAs */
slave_config.dst_addr = (u32)(dma_reg_base + BCM2835_SPI_FIFO);
slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
ret = dmaengine_slave_config(ctlr->dma_tx, &slave_config);
if (ret)
goto err_config;
slave_config.src_addr = (u32)(dma_reg_base + BCM2835_SPI_FIFO);
slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
ret = dmaengine_slave_config(ctlr->dma_rx, &slave_config);
if (ret)
goto err_config;
/* all went well, so set can_dma */
ctlr->can_dma = bcm2835_spi_can_dma;
/* need to do TX AND RX DMA, so we need dummy buffers */
ctlr->flags = SPI_CONTROLLER_MUST_RX | SPI_CONTROLLER_MUST_TX;
return;
err_config:
dev_err(dev, "issue configuring dma: %d - not using DMA mode\n",
ret);
err_release:
bcm2835_dma_release(ctlr);
err:
return;
}
static int bcm2835_spi_transfer_one_poll(struct spi_controller *ctlr,
struct spi_device *spi,
struct spi_transfer *tfr,
u32 cs)
{
struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
unsigned long timeout;
/* update usage statistics */
bs->count_transfer_polling++;
/* enable HW block without interrupts */
bcm2835_wr(bs, BCM2835_SPI_CS, cs | BCM2835_SPI_CS_TA);
/* fill in the fifo before timeout calculations
* if we are interrupted here, then the data is
* getting transferred by the HW while we are interrupted
*/
bcm2835_wr_fifo_blind(bs, BCM2835_SPI_FIFO_SIZE);
/* set the timeout to at least 2 jiffies */
timeout = jiffies + 2 + HZ * polling_limit_us / 1000000;
/* loop until finished the transfer */
while (bs->rx_len) {
/* fill in tx fifo with remaining data */
bcm2835_wr_fifo(bs);
/* read from fifo as much as possible */
bcm2835_rd_fifo(bs);
/* if there is still data pending to read
* then check the timeout
*/
if (bs->rx_len && time_after(jiffies, timeout)) {
dev_dbg_ratelimited(&spi->dev,
"timeout period reached: jiffies: %lu remaining tx/rx: %d/%d - falling back to interrupt mode\n",
jiffies - timeout,
bs->tx_len, bs->rx_len);
/* fall back to interrupt mode */
/* update usage statistics */
bs->count_transfer_irq_after_polling++;
return bcm2835_spi_transfer_one_irq(ctlr, spi,
tfr, cs, false);
}
}
/* Transfer complete - reset SPI HW */
bcm2835_spi_reset_hw(ctlr);
/* and return without waiting for completion */
return 0;
}
static int bcm2835_spi_transfer_one(struct spi_controller *ctlr,
struct spi_device *spi,
struct spi_transfer *tfr)
{
struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
unsigned long spi_hz, clk_hz, cdiv, spi_used_hz;
unsigned long hz_per_byte, byte_limit;
u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);
/* set clock */
spi_hz = tfr->speed_hz;
clk_hz = clk_get_rate(bs->clk);
if (spi_hz >= clk_hz / 2) {
cdiv = 2; /* clk_hz/2 is the fastest we can go */
} else if (spi_hz) {
/* CDIV must be a multiple of two */
cdiv = DIV_ROUND_UP(clk_hz, spi_hz);
cdiv += (cdiv % 2);
if (cdiv >= 65536)
cdiv = 0; /* 0 is the slowest we can go */
} else {
cdiv = 0; /* 0 is the slowest we can go */
}
spi_used_hz = cdiv ? (clk_hz / cdiv) : (clk_hz / 65536);
bcm2835_wr(bs, BCM2835_SPI_CLK, cdiv);
/* handle all the 3-wire mode */
if (spi->mode & SPI_3WIRE && tfr->rx_buf &&
tfr->rx_buf != ctlr->dummy_rx)
cs |= BCM2835_SPI_CS_REN;
else
cs &= ~BCM2835_SPI_CS_REN;
/*
* The driver always uses software-controlled GPIO Chip Select.
* Set the hardware-controlled native Chip Select to an invalid
* value to prevent it from interfering.
*/
cs |= BCM2835_SPI_CS_CS_10 | BCM2835_SPI_CS_CS_01;
/* set transmit buffers and length */
bs->tx_buf = tfr->tx_buf;
bs->rx_buf = tfr->rx_buf;
bs->tx_len = tfr->len;
bs->rx_len = tfr->len;
/* Calculate the estimated time in us the transfer runs. Note that
* there is 1 idle clocks cycles after each byte getting transferred
* so we have 9 cycles/byte. This is used to find the number of Hz
* per byte per polling limit. E.g., we can transfer 1 byte in 30 us
* per 300,000 Hz of bus clock.
*/
hz_per_byte = polling_limit_us ? (9 * 1000000) / polling_limit_us : 0;
byte_limit = hz_per_byte ? spi_used_hz / hz_per_byte : 1;
/* run in polling mode for short transfers */
if (tfr->len < byte_limit)
return bcm2835_spi_transfer_one_poll(ctlr, spi, tfr, cs);
/* run in dma mode if conditions are right
* Note that unlike poll or interrupt mode DMA mode does not have
* this 1 idle clock cycle pattern but runs the spi clock without gaps
*/
if (ctlr->can_dma && bcm2835_spi_can_dma(ctlr, spi, tfr))
return bcm2835_spi_transfer_one_dma(ctlr, spi, tfr, cs);
/* run in interrupt-mode */
return bcm2835_spi_transfer_one_irq(ctlr, spi, tfr, cs, true);
}
static int bcm2835_spi_prepare_message(struct spi_controller *ctlr,
struct spi_message *msg)
{
struct spi_device *spi = msg->spi;
struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
u32 cs = bcm2835_rd(bs, BCM2835_SPI_CS);
int ret;
if (ctlr->can_dma) {
/*
* DMA transfers are limited to 16 bit (0 to 65535 bytes) by
* the SPI HW due to DLEN. Split up transfers (32-bit FIFO
* aligned) if the limit is exceeded.
*/
ret = spi_split_transfers_maxsize(ctlr, msg, 65532,
GFP_KERNEL | GFP_DMA);
if (ret)
return ret;
}
cs &= ~(BCM2835_SPI_CS_CPOL | BCM2835_SPI_CS_CPHA);
if (spi->mode & SPI_CPOL)
cs |= BCM2835_SPI_CS_CPOL;
if (spi->mode & SPI_CPHA)
cs |= BCM2835_SPI_CS_CPHA;
bcm2835_wr(bs, BCM2835_SPI_CS, cs);
return 0;
}
static void bcm2835_spi_handle_err(struct spi_controller *ctlr,
struct spi_message *msg)
{
struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
/* if an error occurred and we have an active dma, then terminate */
if (cmpxchg(&bs->dma_pending, true, false)) {
dmaengine_terminate_sync(ctlr->dma_tx);
dmaengine_terminate_sync(ctlr->dma_rx);
bcm2835_spi_undo_prologue(bs);
}
/* and reset */
bcm2835_spi_reset_hw(ctlr);
}
static int chip_match_name(struct gpio_chip *chip, void *data)
{
return !strcmp(chip->label, data);
}
static int bcm2835_spi_setup(struct spi_device *spi)
{
int err;
struct gpio_chip *chip;
/*
* sanity checking the native-chipselects
*/
if (spi->mode & SPI_NO_CS)
return 0;
if (gpio_is_valid(spi->cs_gpio))
return 0;
if (spi->chip_select > 1) {
/* error in the case of native CS requested with CS > 1
* officially there is a CS2, but it is not documented
* which GPIO is connected with that...
*/
dev_err(&spi->dev,
"setup: only two native chip-selects are supported\n");
return -EINVAL;
}
/* now translate native cs to GPIO */
/* get the gpio chip for the base */
chip = gpiochip_find("pinctrl-bcm2835", chip_match_name);
if (!chip)
return 0;
/* and calculate the real CS */
spi->cs_gpio = chip->base + 8 - spi->chip_select;
/* and set up the "mode" and level */
dev_info(&spi->dev, "setting up native-CS%i as GPIO %i\n",
spi->chip_select, spi->cs_gpio);
/* set up GPIO as output and pull to the correct level */
err = gpio_direction_output(spi->cs_gpio,
(spi->mode & SPI_CS_HIGH) ? 0 : 1);
if (err) {
dev_err(&spi->dev,
"could not set CS%i gpio %i as output: %i",
spi->chip_select, spi->cs_gpio, err);
return err;
}
return 0;
}
static int bcm2835_spi_probe(struct platform_device *pdev)
{
struct spi_controller *ctlr;
struct bcm2835_spi *bs;
struct resource *res;
int err;
ctlr = spi_alloc_master(&pdev->dev, sizeof(*bs));
if (!ctlr)
return -ENOMEM;
platform_set_drvdata(pdev, ctlr);
ctlr->mode_bits = BCM2835_SPI_MODE_BITS;
ctlr->bits_per_word_mask = SPI_BPW_MASK(8);
ctlr->num_chipselect = 3;
ctlr->setup = bcm2835_spi_setup;
ctlr->transfer_one = bcm2835_spi_transfer_one;
ctlr->handle_err = bcm2835_spi_handle_err;
ctlr->prepare_message = bcm2835_spi_prepare_message;
ctlr->dev.of_node = pdev->dev.of_node;
bs = spi_controller_get_devdata(ctlr);
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
bs->regs = devm_ioremap_resource(&pdev->dev, res);
if (IS_ERR(bs->regs)) {
err = PTR_ERR(bs->regs);
goto out_controller_put;
}
bs->clk = devm_clk_get(&pdev->dev, NULL);
if (IS_ERR(bs->clk)) {
err = PTR_ERR(bs->clk);
dev_err(&pdev->dev, "could not get clk: %d\n", err);
goto out_controller_put;
}
bs->irq = platform_get_irq(pdev, 0);
if (bs->irq <= 0) {
dev_err(&pdev->dev, "could not get IRQ: %d\n", bs->irq);
err = bs->irq ? bs->irq : -ENODEV;
goto out_controller_put;
}
clk_prepare_enable(bs->clk);
bcm2835_dma_init(ctlr, &pdev->dev);
/* initialise the hardware with the default polarities */
bcm2835_wr(bs, BCM2835_SPI_CS,
BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);
err = devm_request_irq(&pdev->dev, bs->irq, bcm2835_spi_interrupt, 0,
dev_name(&pdev->dev), ctlr);
if (err) {
dev_err(&pdev->dev, "could not request IRQ: %d\n", err);
goto out_clk_disable;
}
err = devm_spi_register_controller(&pdev->dev, ctlr);
if (err) {
dev_err(&pdev->dev, "could not register SPI controller: %d\n",
err);
goto out_clk_disable;
}
bcm2835_debugfs_create(bs, dev_name(&pdev->dev));
return 0;
out_clk_disable:
clk_disable_unprepare(bs->clk);
out_controller_put:
spi_controller_put(ctlr);
return err;
}
static int bcm2835_spi_remove(struct platform_device *pdev)
{
struct spi_controller *ctlr = platform_get_drvdata(pdev);
struct bcm2835_spi *bs = spi_controller_get_devdata(ctlr);
bcm2835_debugfs_remove(bs);
/* Clear FIFOs, and disable the HW block */
bcm2835_wr(bs, BCM2835_SPI_CS,
BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);
clk_disable_unprepare(bs->clk);
bcm2835_dma_release(ctlr);
return 0;
}
static const struct of_device_id bcm2835_spi_match[] = {
{ .compatible = "brcm,bcm2835-spi", },
{}
};
MODULE_DEVICE_TABLE(of, bcm2835_spi_match);
static struct platform_driver bcm2835_spi_driver = {
.driver = {
.name = DRV_NAME,
.of_match_table = bcm2835_spi_match,
},
.probe = bcm2835_spi_probe,
.remove = bcm2835_spi_remove,
};
module_platform_driver(bcm2835_spi_driver);
MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835");
MODULE_AUTHOR("Chris Boot <bootc@bootc.net>");
MODULE_LICENSE("GPL");
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