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spi: atmel: add support for changing message transfer speed 

The only speed available was max_speed (the maximum speed declared for a
device).
This patch adds the support for spi_tranfer->speed_hz parameter.
We can now set a different speed for each spi message.

Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
This commit is contained in:
Richard Genoud 2013-11-07 10:34:06 +01:00 committed by Mark Brown
parent 9f87d6f26b
commit d3b72c7e6b
1 changed files with 55 additions and 37 deletions
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92
drivers/spi/spi-atmel.c
View File

@ -694,6 +694,54 @@ static void atmel_spi_next_xfer_data(struct spi_master *master,
*plen = len;
}
static int atmel_spi_set_xfer_speed(struct atmel_spi *as,
struct spi_device *spi,
struct spi_transfer *xfer)
{
u32 scbr, csr;
unsigned long bus_hz;
/* v1 chips start out at half the peripheral bus speed. */
bus_hz = clk_get_rate(as->clk);
if (!atmel_spi_is_v2(as))
bus_hz /= 2;
/*
* Calculate the lowest divider that satisfies the
* constraint, assuming div32/fdiv/mbz == 0.
*/
if (xfer->speed_hz)
scbr = DIV_ROUND_UP(bus_hz, xfer->speed_hz);
else
/*
* This can happend if max_speed is null.
* In this case, we set the lowest possible speed
*/
scbr = 0xff;
/*
* If the resulting divider doesn't fit into the
* register bitfield, we can't satisfy the constraint.
*/
if (scbr >= (1 << SPI_SCBR_SIZE)) {
dev_err(&spi->dev,
"setup: %d Hz too slow, scbr %u; min %ld Hz\n",
xfer->speed_hz, scbr, bus_hz/255);
return -EINVAL;
}
if (scbr == 0) {
dev_err(&spi->dev,
"setup: %d Hz too high, scbr %u; max %ld Hz\n",
xfer->speed_hz, scbr, bus_hz);
return -EINVAL;
}
csr = spi_readl(as, CSR0 + 4 * spi->chip_select);
csr = SPI_BFINS(SCBR, scbr, csr);
spi_writel(as, CSR0 + 4 * spi->chip_select, csr);
return 0;
}
/*
* Submit next transfer for PDC.
* lock is held, spi irq is blocked
@ -731,6 +779,8 @@ static void atmel_spi_pdc_next_xfer(struct spi_master *master,
spi_writel(as, RCR, len);
spi_writel(as, TCR, len);
atmel_spi_set_xfer_speed(as, msg->spi, xfer);
dev_dbg(&msg->spi->dev,
" start xfer %p: len %u tx %p/%08llx rx %p/%08llx\n",
xfer, xfer->len, xfer->tx_buf,
@ -823,6 +873,7 @@ static void atmel_spi_dma_next_xfer(struct spi_master *master,
as->current_transfer = xfer;
len = xfer->len;
atmel_spi_set_xfer_speed(as, msg->spi, xfer);
}
if (atmel_spi_use_dma(as, xfer)) {
@ -1264,9 +1315,8 @@ static int atmel_spi_setup(struct spi_device *spi)
{
struct atmel_spi *as;
struct atmel_spi_device *asd;
u32 scbr, csr;
u32 csr;
unsigned int bits = spi->bits_per_word;
unsigned long bus_hz;
unsigned int npcs_pin;
int ret;
@ -1290,33 +1340,7 @@ static int atmel_spi_setup(struct spi_device *spi)
return -EINVAL;
}
/* v1 chips start out at half the peripheral bus speed. */
bus_hz = clk_get_rate(as->clk);
if (!atmel_spi_is_v2(as))
bus_hz /= 2;
if (spi->max_speed_hz) {
/*
* Calculate the lowest divider that satisfies the
* constraint, assuming div32/fdiv/mbz == 0.
*/
scbr = DIV_ROUND_UP(bus_hz, spi->max_speed_hz);
/*
* If the resulting divider doesn't fit into the
* register bitfield, we can't satisfy the constraint.
*/
if (scbr >= (1 << SPI_SCBR_SIZE)) {
dev_dbg(&spi->dev,
"setup: %d Hz too slow, scbr %u; min %ld Hz\n",
spi->max_speed_hz, scbr, bus_hz/255);
return -EINVAL;
}
} else
/* speed zero means "as slow as possible" */
scbr = 0xff;
csr = SPI_BF(SCBR, scbr) | SPI_BF(BITS, bits - 8);
csr = SPI_BF(BITS, bits - 8);
if (spi->mode & SPI_CPOL)
csr |= SPI_BIT(CPOL);
if (!(spi->mode & SPI_CPHA))
@ -1363,8 +1387,8 @@ static int atmel_spi_setup(struct spi_device *spi)
asd->csr = csr;
dev_dbg(&spi->dev,
"setup: %lu Hz bpw %u mode 0x%x -> csr%d %08x\n",
bus_hz / scbr, bits, spi->mode, spi->chip_select, csr);
"setup: bpw %u mode 0x%x -> csr%d %08x\n",
bits, spi->mode, spi->chip_select, csr);
if (!atmel_spi_is_v2(as))
spi_writel(as, CSR0 + 4 * spi->chip_select, csr);
@ -1414,12 +1438,6 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg)
}
}
/* FIXME implement these protocol options!! */
if (xfer->speed_hz < spi->max_speed_hz) {
dev_dbg(&spi->dev, "can't change speed in transfer\n");
return -ENOPROTOOPT;
}
/*
* DMA map early, for performance (empties dcache ASAP) and
* better fault reporting.