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linux-sg2042
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hsu: add a periodic timer to check dma rx channel 

A general problem for uart rx dma channel is you never know when
and how much data will be received, so usually preset it a DMA
descriptor with a big size, and rely on DMA RX timeout IRQ to
know there is some data in rx channel.

For a RX data size of multiple of MOTSR, there will be no timeout
IRQ issued, thus OS will never be notified about that.

This is a work around for that, current timer frequency is 5 times
per second, it should vary according to the baud rate

When future silicon version fix the problem, this workaround need
be removed

Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Feng Tang 2010-07-27 08:20:32 +01:00 committed by Greg Kroah-Hartman
parent d843fc6e9d
commit 669b7a0938
1 changed files with 48 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
drivers/serial/mfd.c
View File

@ -64,6 +64,8 @@
#define mfd_readl(obj, offset) readl(obj->reg + offset)
#define mfd_writel(obj, offset, val) writel(val, obj->reg + offset)
#define HSU_DMA_TIMEOUT_CHECK_FREQ (HZ/10)
struct hsu_dma_buffer {
u8 *buf;
dma_addr_t dma_addr;
@ -76,6 +78,7 @@ struct hsu_dma_chan {
u32 dirt; /* to or from device */
struct uart_hsu_port *uport;
void __iomem *reg;
struct timer_list rx_timer; /* only needed by RX channel */
};
struct uart_hsu_port {
@ -377,6 +380,8 @@ void hsu_dma_start_rx_chan(struct hsu_dma_chan *rxc, struct hsu_dma_buffer *dbuf
| (0x1 << 24) /* timeout bit, see HSU Errata 1 */
);
chan_writel(rxc, HSU_CH_CR, 0x3);
mod_timer(&rxc->rx_timer, jiffies + HSU_DMA_TIMEOUT_CHECK_FREQ);
}
/* Protected by spin_lock_irqsave(port->lock) */
@ -437,8 +442,13 @@ void hsu_dma_rx(struct uart_hsu_port *up, u32 int_sts)
/* We can use 2 ways to calc the actual transfer len */
count = chan_readl(chan, HSU_CH_D0SAR) - dbuf->dma_addr;
if (!count)
if (!count) {
/* restart the channel before we leave */
chan_writel(chan, HSU_CH_CR, 0x3);
return;
}
del_timer(&chan->rx_timer);
dma_sync_single_for_cpu(port->dev, dbuf->dma_addr,
dbuf->dma_size, DMA_FROM_DEVICE);
@ -463,9 +473,12 @@ void hsu_dma_rx(struct uart_hsu_port *up, u32 int_sts)
| (0x1 << 16)
| (0x1 << 24) /* timeout bit, see HSU Errata 1 */
);
chan_writel(chan, HSU_CH_CR, 0x3);
tty_flip_buffer_push(tty);
chan_writel(chan, HSU_CH_CR, 0x3);
chan->rx_timer.expires = jiffies + HSU_DMA_TIMEOUT_CHECK_FREQ;
add_timer(&chan->rx_timer);
}
static void serial_hsu_stop_rx(struct uart_port *port)
@ -893,6 +906,8 @@ static void serial_hsu_shutdown(struct uart_port *port)
container_of(port, struct uart_hsu_port, port);
unsigned long flags;
del_timer_sync(&up->rxc->rx_timer);
/* Disable interrupts from this port */
up->ier = 0;
serial_out(up, UART_IER, 0);
@ -1348,6 +1363,28 @@ err_disable:
return ret;
}
static void hsu_dma_rx_timeout(unsigned long data)
{
struct hsu_dma_chan *chan = (void *)data;
struct uart_hsu_port *up = chan->uport;
struct hsu_dma_buffer *dbuf = &up->rxbuf;
int count = 0;
unsigned long flags;
spin_lock_irqsave(&up->port.lock, flags);
count = chan_readl(chan, HSU_CH_D0SAR) - dbuf->dma_addr;
if (!count) {
mod_timer(&chan->rx_timer, jiffies + HSU_DMA_TIMEOUT_CHECK_FREQ);
goto exit;
}
hsu_dma_rx(up, 0);
exit:
spin_unlock_irqrestore(&up->port.lock, flags);
}
static void hsu_global_init(void)
{
struct hsu_port *hsu;
@ -1409,6 +1446,13 @@ static void hsu_global_init(void)
dchan->uport = &hsu->port[i/2];
dchan->reg = hsu->reg + HSU_DMA_CHANS_REG_OFFSET +
i * HSU_DMA_CHANS_REG_LENGTH;
/* Work around for RX */
if (dchan->dirt == DMA_FROM_DEVICE) {
init_timer(&dchan->rx_timer);
dchan->rx_timer.function = hsu_dma_rx_timeout;
dchan->rx_timer.data = (unsigned long)dchan;
}
dchan++;
}