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authorFeng Tang <feng.tang@intel.com>2010-07-27 08:20:32 +0100
committerGreg Kroah-Hartman <gregkh@suse.de>2010-08-10 13:47:46 -0700
commit669b7a0938e759097c150400cd36bd49befaf5bb (patch)
treeb7244699ea1e8bf04c50dde2b9efeaf504f44bc6 /drivers/serial
parentd843fc6e9dc9bee7061b6833594860ea93ad98e1 (diff)
downloadlinux-669b7a0938e759097c150400cd36bd49befaf5bb.tar.bz2
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>
Diffstat (limited to 'drivers/serial')
-rw-r--r--drivers/serial/mfd.c50
1 files changed, 47 insertions, 3 deletions
diff --git a/drivers/serial/mfd.c b/drivers/serial/mfd.c
index 300dcb134e07..ed2bf6b14a4a 100644
--- a/drivers/serial/mfd.c
+++ b/drivers/serial/mfd.c
@@ -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;
@@ -75,7 +77,8 @@ struct hsu_dma_chan {
u32 id;
u32 dirt; /* to or from device */
struct uart_hsu_port *uport;
- void __iomem *reg;
+ 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 */
);
+ 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);
- tty_flip_buffer_push(tty);
}
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++;
}