From: peter@hurleysoftware.com (Peter Hurley)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 09/16] tty: serial: 8250_dma: Add a TX trigger workaround for AM33xx
Date: Tue, 23 Sep 2014 13:03:51 -0400 [thread overview]
Message-ID: <5421A7F7.3070109@hurleysoftware.com> (raw)
In-Reply-To: <20140921204100.GA10111@linutronix.de>
On 09/21/2014 04:41 PM, Sebastian Andrzej Siewior wrote:
> * Frans Klaver | 2014-09-17 12:28:12 [+0200]:
>
>> - Bone Black: Yocto poky, core-image-minimal
>> Login, "less file" locks up, doesn't show anything. I can exit using
>> Ctrl-C.
>
> So I have the same with my and the serial-omap driver. No difference
> here. The trace looks like this:
> | <idle>-0 [000] d.h. 444.393585: serial8250_handle_irq: iir cc lsr 61
> | <idle>-0 [000] d.h. 444.393605: serial8250_rx_chars: get 0d
> received the enter key
>
> | <idle>-0 [000] d.h. 444.393609: serial8250_rx_chars: insert d lsr 61
> | <idle>-0 [000] d.h. 444.393614: uart_insert_char: 1
> | <idle>-0 [000] d.h. 444.393617: uart_insert_char: 2
> | <idle>-0 [000] dnh. 444.393636: serial8250_tx_chars: empty
> | kworker/0:2-753 [000] d... 444.393686: serial8250_start_tx: empty?1
> | kworker/0:2-753 [000] d.h. 444.393699: serial8250_handle_irq: iir c2 lsr 60
> | kworker/0:2-753 [000] d.h. 444.393705: serial8250_tx_chars: empty
> | sh-1042 [000] d... 444.393822: serial8250_start_tx: empty?1
> | sh-1042 [000] d.h. 444.393836: serial8250_handle_irq: iir c2 lsr 60
> | sh-1042 [000] d.h. 444.393842: serial8250_tx_chars: empty
> | sh-1042 [000] d... 444.393855: serial8250_start_tx: empty?0
> | sh-1042 [000] d.h. 444.393863: serial8250_handle_irq: iir c2 lsr 60
> | sh-1042 [000] d.h. 444.393867: serial8250_tx_chars: put 0d
> | sh-1042 [000] d.h. 444.393871: serial8250_tx_chars: put 0a
>
> shell responded with "\r\n" which I see and then
>
> | sh-1042 [000] d.h. 444.394057: serial8250_handle_irq: iir c2 lsr 60
> | sh-1042 [000] d.h. 444.394065: serial8250_tx_chars: empty
>
> nothing more. less isn't sending data for some reason. Exactly the same
> thing happens in a Debian environment except that it continues:
> ?
> | bash-2468 [000] d.h. 99.657899: serial8250_tx_chars: put 0a
> | bash-2468 [000] d.h. 99.658089: serial8250_handle_irq: iir c2 lsr 60
> | bash-2468 [000] d.h. 99.658095: serial8250_tx_chars: empty
> =>
> | less-2474 [000] d... 99.696038: serial8250_start_tx: empty?0
> | less-2474 [000] d.h. 99.696069: serial8250_handle_irq: iir c2 lsr 60
> | less-2474 [000] d.h. 99.696078: serial8250_tx_chars: put 1b
> | less-2474 [000] d.h. 99.696082: serial8250_tx_chars: put 5b
> | less-2474 [000] d.h. 99.696085: serial8250_tx_chars: put 3f
> | less-2474 [000] d.h. 99.696087: serial8250_tx_chars: put 31
>
> It has to be something about the environment. Booting Debian and chroot
> into this RFS and less works perfectly. But since it behaves like that
> with both drivers, I guess the problem is somewhere else?
>
>> vi runs normally, only occupies part of the total screen estate in
>> minicom. After quitting, a weird character shows up (typically I see
>> ? there), but minicom can use the rest of the screen estate again.
>> If we disregard the odd character, this is much like the behavior we
>> have on the omap-serial driver.
>> - Custom board: Yocto poky, custom image
>> Login, "less file" locks up, showing only "?" in the top left corner
>> of the screen. Can get out of there by having something dumped through
>> /dev/kmsg.
>
> I managed to run into something like that with vi on dra7 and with
> little more patience on am335x as well by "vi *" and then ":n".
>
> This gets fixed indeed by writing. Hours of debugging and a lot of hair
> less later: the yocto RFS calls set_termios quite a lot.
readline() does this; it 'saves' the caller's termios, sets termios
for non-canonical reads, reads one char, and 'restores' the caller's
termios.
> This includes
> changing the baudrate (not by yocto but the driver sets it to 0 and then
> to the requested one) and this seems to be responsible for the "bad
> bytes". I haven't figured out yet I don't see this with omap-serial.
> Even worse: If this (set_termios()) happens while the DMA is still
> active then it might stall it. A write into the FIFO seems to fix it and
> this is where your "echo >/dev/kmsg" fixes things.
> If I delay the restore_registers part of set_termios() until TX-DMA is
> complete then it seems that the TX-DMA stall does not tall anymore.
The tty core calls the driver's wait_until_sent() method before changing
the termios (if TCSADRAIN is used for tcsetattr(), which I think for readline()
it does).
But DMA is cheating if the UART driver's tx_empty() method is saying the
transmitter is empty while TX DMA is still running.
Regards,
Peter Hurley
next prev parent reply other threads:[~2014-09-23 17:03 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
2014-10-13 14:55 ` Frans Klaver
2014-09-23 17:03 ` Peter Hurley [this message]
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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