From: bigeasy@linutronix.de (Sebastian Andrzej Siewior)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 09/16] tty: serial: 8250_dma: Add a TX trigger workaround for AM33xx
Date: Thu, 2 Oct 2014 12:27:23 +0200 [thread overview]
Message-ID: <20141002102723.GB23661@linutronix.de> (raw)
In-Reply-To: <20140930084416.GB31111@ci00147.xsens-tech.local>
* Frans Klaver | 2014-09-30 10:44:16 [+0200]:
>On Mon, Sep 29, 2014 at 12:30:43PM +0200, Frans Klaver wrote:
>> On Mon, Sep 29, 2014 at 11:54:40AM +0200, Sebastian Andrzej Siewior wrote:
>> > For your "too much work for irq" problem: Could you add trace_printk()
>> > in tx/rx dma start/complete, and irq routine? The interresting part is
>> > what is the irq routine doing once entered. It might be a condition that
>> > is ignored at first and "acked" later while serving another event. Or it
>> > is really doing something and this is more or less "legal".
>>
>
>Here's some trace output I get. I hope branches become clear by the
>calls they do.
>
> uart_test-482 [000] .ns. 17.860139: __dma_rx_do_complete: error: 0, uart_bug_dma: 32
> uart_test-482 [000] .ns. 17.860141: __dma_rx_do_complete: rx_dma(p, 0)
these two happen outside the IRQ routine for every 48 bytes.
?
> uart_test-483 [000] dnh. 17.861018: serial8250_interrupt: irq 89
> uart_test-483 [000] dnh. 17.861026: serial8250_interrupt: 89 e
e? Did was the routine invoked 0xe times or this a register?
> uart_test-483 [000] .ns. 17.861045: __dma_rx_do_complete: error: 0, uart_bug_dma: 32
> uart_test-483 [000] .ns. 17.861047: __dma_rx_do_complete: rx_dma(p, 0)
another 48bytes
> uart_test-479 [000] d.H. 17.861124: serial8250_interrupt: irq 89
> uart_test-479 [000] d.H. 17.861133: serial8250_handle_irq: l1 IIR cc LSR 61
> uart_test-479 [000] d.H. 17.861135: serial8250_handle_irq: rx_dma(up, iir)
> uart_test-479 [000] d.H. 17.861139: serial8250_rx_dma: l1, UART_IIR_RX_TIMEOUT
> uart_test-479 [000] d.H. 17.861147: __dma_rx_do_complete: error: 1, uart_bug_dma: 32
> uart_test-479 [000] d.H. 17.861150: serial8250_handle_irq: rx_chars(up, status)
> uart_test-479 [000] d.H. 17.861190: serial8250_handle_irq: rx_dma(up, 0)
timeout, manual purge. Do you have an idea how many bytes were manually
received?
> uart_test-479 [000] d.H. 17.861205: serial8250_interrupt: 89 e
> kworker/0:1-10 [000] dnH. 17.864949: serial8250_interrupt: irq 89
>
>So far so good. We're just entered interrupt where stuff goes awry. The
>following pattern repeats over 600 times:
>
> kworker/0:1-10 [000] dnH. 17.865198: serial8250_handle_irq: l1 IIR cc LSR 61
> kworker/0:1-10 [000] dnH. 17.865254: serial8250_handle_irq: rx_dma(up, iir)
> kworker/0:1-10 [000] dnH. 17.865333: serial8250_rx_dma: l1, UART_IIR_RX_TIMEOUT
> kworker/0:1-10 [000] dnH. 17.865626: __dma_rx_do_complete: error: 1, uart_bug_dma: 32
> kworker/0:1-10 [000] dnH. 17.865747: serial8250_handle_irq: rx_chars(up, status)
> kworker/0:1-10 [000] dnH. 17.868797: serial8250_handle_irq: rx_dma(up, 0)
>
>ending with:
>
> kworker/0:1-10 [000] dnH. 20.027093: serial8250_interrupt: serial8250: too much work for irq89
> kworker/0:1-10 [000] dnH. 20.027181: serial8250_interrupt: 89 e
>
>This clogs the entire system until I disconnect the communication lines.
>
>So we get an RX timeout. The receiver fifo trigger level was not reached
>and 8250_core is left to copy the remaining data. I would expect that if
>the trigger level wasn't reached, we wouldn't need to be doing this that
>often. On the other hand, could we be trapped reading data from rx
>without dma helping us? And how could we resolve this?
So if I understand you correct, then you enter serial8250_interrupt()
and then you enter multiple times omap_8250_dma_handle_irq() and
you always get a TIMEOUT event and fetch byte(s) manualy via
serial8250_rx_chars(). And after one iteration UART_IIR_NO_INT is not
set and you do it again, right?
I have no idea when exactly the timeout-interrupt fires. The manual
says: "? the count is reset when there is activity on uarti_rx ?" but it
does not say how often it increments before the level is reached.
It also might be that you have a small gap between two bytes and this
high baud rate the gap is considered as a timeout event.
Another thing could be that if the we enqueue a RX transfer from the
dma_completion callback then we have too many bytes in the FIFO already
becahse the callback is invoked from softirq. What happens if we cut the
middle man via
diff --git a/drivers/dma/virt-dma.c b/drivers/dma/virt-dma.c
index 6f80432..21b04bd 100644
--- a/drivers/dma/virt-dma.c
+++ b/drivers/dma/virt-dma.c
@@ -63,8 +63,9 @@ static void vchan_complete(unsigned long arg)
dma_async_tx_callback cb = NULL;
void *cb_data = NULL;
LIST_HEAD(head);
+ unsigned long flags;
- spin_lock_irq(&vc->lock);
+ spin_lock_irqsave(&vc->lock, flags);
list_splice_tail_init(&vc->desc_completed, &head);
vd = vc->cyclic;
if (vd) {
@@ -72,7 +73,7 @@ static void vchan_complete(unsigned long arg)
cb = vd->tx.callback;
cb_data = vd->tx.callback_param;
}
- spin_unlock_irq(&vc->lock);
+ spin_unlock_irqrestore(&vc->lock, flags);
if (cb)
cb(cb_data);
diff --git a/drivers/dma/virt-dma.h b/drivers/dma/virt-dma.h
index 181b952..7632338 100644
--- a/drivers/dma/virt-dma.h
+++ b/drivers/dma/virt-dma.h
@@ -92,7 +92,10 @@ static inline void vchan_cookie_complete(struct virt_dma_desc *vd)
vd, cookie);
list_add_tail(&vd->node, &vc->desc_completed);
- tasklet_schedule(&vc->task);
+ if (vd->tx.my_uart)
+ vc->task.func(vc);
+ else
+ tasklet_schedule(&vc->task);
}
/**
diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index 57a8b12..5d7ee92 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -728,6 +728,7 @@ static int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
dma->rx_running = 1;
desc->callback = __dma_rx_complete;
desc->callback_param = p;
+ desc->my_uart = 1;
dma->rx_cookie = dmaengine_submit(desc);
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 1f9e642..0f5fbe1 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -459,6 +459,7 @@ struct dmaengine_unmap_data {
struct dma_async_tx_descriptor {
dma_cookie_t cookie;
enum dma_ctrl_flags flags; /* not a 'long' to pack with cookie */
+ u32 my_uart;
dma_addr_t phys;
struct dma_chan *chan;
dma_cookie_t (*tx_submit)(struct dma_async_tx_descriptor *tx);
>
>Frans
Sebastian
next prev parent reply other threads:[~2014-10-02 10:27 UTC|newest]
Thread overview: 97+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-10 19:29 [PATCH 00/16 v9] omap 8250 based uart + DMA Sebastian Andrzej Siewior
2014-09-10 19:29 ` [PATCH 01/16] tty: serial: 8250_core: allow to set ->throttle / ->unthrottle callbacks Sebastian Andrzej Siewior
2014-09-10 19:29 ` [PATCH 02/16] tty: serial: 8250_core: add run time pm Sebastian Andrzej Siewior
2014-09-29 9:46 ` Frans Klaver
2014-09-29 13:39 ` Sebastian Andrzej Siewior
2014-09-10 19:29 ` [PATCH 03/16] tty: serial: 8250_core: read only RX if there is something in the FIFO Sebastian Andrzej Siewior
2015-02-09 13:34 ` Nicolas Schichan
2015-02-09 23:34 ` Peter Hurley
2015-02-10 9:32 ` Sebastian Andrzej Siewior
2015-02-10 12:04 ` Nicolas Schichan
2015-02-10 17:46 ` Peter Hurley
2015-02-11 20:01 ` Peter Hurley
2015-02-11 20:03 ` Tony Lindgren
2015-02-11 20:42 ` Peter Hurley
2015-02-12 8:45 ` Sebastian Andrzej Siewior
2015-02-12 9:40 ` Russell King - ARM Linux
2015-02-12 16:32 ` Peter Hurley
2015-02-12 19:23 ` Sebastian Andrzej Siewior
2015-02-12 19:55 ` Peter Hurley
2015-02-12 20:34 ` Sebastian Andrzej Siewior
2015-02-13 18:51 ` Sebastian Andrzej Siewior
2015-02-13 23:15 ` Russell King - ARM Linux
2015-02-15 17:32 ` [PATCH] serial: 8250: Revert "tty: serial: 8250_core: read only RX if there is something in the FIFO" Sebastian Andrzej Siewior
2015-05-12 20:25 ` Tony Lindgren
2014-09-10 19:29 ` [PATCH 04/16] tty: serial: 8250_core: use the ->line argument as a hint in serial8250_find_match_or_unused() Sebastian Andrzej Siewior
2014-09-10 19:30 ` [PATCH 05/16] tty: serial: 8250_core: remove UART_IER_RDI in serial8250_stop_rx() Sebastian Andrzej Siewior
2014-09-11 11:19 ` Heikki Krogerus
2014-09-10 19:30 ` [PATCH 06/16] tty: serial: Add 8250-core based omap driver Sebastian Andrzej Siewior
2014-09-11 11:57 ` Peter Hurley
2014-09-16 17:01 ` Sebastian Andrzej Siewior
2014-09-29 9:38 ` Frans Klaver
2014-09-29 13:27 ` Sebastian Andrzej Siewior
2014-09-29 13:34 ` Frans Klaver
2014-09-10 19:30 ` [PATCH 07/16] tty: serial: 8250_dma: handle error on TX submit Sebastian Andrzej Siewior
2014-09-10 19:30 ` [PATCH 08/16] tty: serial: 8250_dma: enqueue RX dma again on completion Sebastian Andrzej Siewior
2014-09-10 19:30 ` [PATCH 09/16] tty: serial: 8250_dma: Add a TX trigger workaround for AM33xx Sebastian Andrzej Siewior
2014-09-11 11:17 ` Heikki Krogerus
2014-09-11 11:42 ` Sebastian Andrzej Siewior
2014-09-11 12:32 ` Peter Hurley
2014-09-11 12:50 ` Sebastian Andrzej Siewior
2014-09-11 14:35 ` Peter Hurley
2014-09-15 17:01 ` Sebastian Andrzej Siewior
2014-09-16 16:55 ` Sebastian Andrzej Siewior
2014-09-17 12:20 ` Peter Hurley
2014-09-17 16:25 ` Sebastian Andrzej Siewior
2014-09-29 16:15 ` Sebastian Andrzej Siewior
2014-09-11 15:11 ` Frans Klaver
2014-09-11 16:04 ` Sebastian Andrzej Siewior
2014-09-11 17:04 ` Frans Klaver
2014-09-12 7:23 ` Sebastian Andrzej Siewior
[not found] ` <20140912094010.GE28458@ci00147.xsens-tech.local>
2014-09-12 9:51 ` Sebastian Andrzej Siewior
2014-09-12 10:28 ` Frans Klaver
2014-09-15 16:42 ` Sebastian Andrzej Siewior
2014-09-16 9:05 ` Frans Klaver
2014-09-16 12:42 ` Frans Klaver
2014-09-16 14:23 ` Frans Klaver
2014-09-17 10:28 ` Frans Klaver
2014-09-21 20:41 ` Sebastian Andrzej Siewior
2014-09-22 9:28 ` Frans Klaver
2014-09-24 7:56 ` Sebastian Andrzej Siewior
2014-09-25 15:14 ` Sebastian Andrzej Siewior
2014-09-25 15:18 ` Frans Klaver
2014-09-29 8:50 ` Frans Klaver
2014-09-29 9:54 ` Sebastian Andrzej Siewior
2014-09-29 10:30 ` Frans Klaver
2014-09-30 8:44 ` Frans Klaver
2014-10-02 10:27 ` Sebastian Andrzej Siewior [this message]
2014-10-13 14:55 ` Frans Klaver
2014-09-23 17:03 ` Peter Hurley
2014-09-24 7:53 ` Sebastian Andrzej Siewior
2014-09-25 10:42 ` Sebastian Andrzej Siewior
2014-09-25 11:31 ` Peter Hurley
2014-09-25 13:11 ` Sebastian Andrzej Siewior
2014-09-17 16:34 ` Sebastian Andrzej Siewior
2014-09-19 10:22 ` Heikki Krogerus
2014-09-19 10:58 ` Sebastian Andrzej Siewior
2014-09-19 11:25 ` Peter Hurley
2014-09-22 7:46 ` Heikki Krogerus
2014-09-25 9:24 ` Sebastian Andrzej Siewior
2014-09-10 19:30 ` [PATCH 10/16] tty: serial: 8250_dma: optimize the xmit path due to UART_BUG_DMA_TX Sebastian Andrzej Siewior
2014-09-10 19:30 ` [PATCH 11/16] tty: serial: 8250_dma: keep own book keeping about RX transfers Sebastian Andrzej Siewior
2014-09-10 19:30 ` [PATCH 12/16] tty: serial: 8250_dma: handle the UART RDI event while DMA remains idle Sebastian Andrzej Siewior
2014-09-29 9:23 ` Frans Klaver
2014-09-10 19:30 ` [PATCH 13/16] tty: serial: 8250_dma: add pm runtime Sebastian Andrzej Siewior
2014-09-29 9:26 ` Frans Klaver
2014-09-29 9:56 ` Sebastian Andrzej Siewior
2014-09-10 19:30 ` [PATCH 14/16] arm: dts: am33xx: add DMA properties for UART Sebastian Andrzej Siewior
2014-09-10 19:30 ` [PATCH 15/16] arm: dts: dra7: " Sebastian Andrzej Siewior
2014-09-10 19:30 ` [PATCH 16/16] tty: serial: 8250: omap: add dma support Sebastian Andrzej Siewior
2014-09-12 22:43 ` [PATCH 00/16 v9] omap 8250 based uart + DMA Tony Lindgren
2014-09-15 11:50 ` Sebastian Andrzej Siewior
2014-09-16 12:57 ` Sebastian Andrzej Siewior
2014-09-16 16:48 ` Tony Lindgren
2014-09-16 21:30 ` Tony Lindgren
2014-09-17 8:38 ` Sebastian Andrzej Siewior
2014-09-17 9:05 ` Sebastian Andrzej Siewior
2014-09-26 16:02 ` Greg KH
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