From 669b7a0938e759097c150400cd36bd49befaf5bb Mon Sep 17 00:00:00 2001 From: Feng Tang Date: Tue, 27 Jul 2010 08:20:32 +0100 Subject: 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 Signed-off-by: Alan Cox Signed-off-by: Greg Kroah-Hartman --- drivers/serial/mfd.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 47 insertions(+), 3 deletions(-) (limited to 'drivers/serial/mfd.c') 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++; } -- cgit v1.2.2