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Re: [PATCH] tty: serial: 8250_omap: do not defer termios changes

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On 04/11/2016 07:53 PM, Peter Hurley wrote:
> On 04/11/2016 01:18 AM, John Ogness wrote:
>> On 2016-04-05, Peter Hurley <peter@hurleysoftware.com> wrote:
>>> On 03/31/2016 01:41 AM, John Ogness wrote:
>>>> It has been observed that the TX-DMA can stall
>>>
>>> Does this happen on any other OMAP part besides am335x?
>>> I looked back over the LKML history of this and didn't see
>>> any other design implicated in this problem.
>>
>> I just ran the tests again using 4.6-rc2. I am able to reproduce the
>> dma-tx stall with am335x/edma and dra7/sdma.
> 
> I thought we already established sdma was not to be used since
> the hardware does not actually support pausing without data loss.

This workaround was not invented for sdma but for edma (with am335x).

> http://www.spinics.net/lists/linux-serial/msg18503.html

This could be fixed. See
  http://www.spinics.net/lists/linux-serial/msg18517.html
  http://www.spinics.net/lists/linux-serial/msg18531.html

rmk was fine with it from what I read. So what is missing is just
refurbish the patch (update the comment according to rmk replay) and
then we could re-enable DMA again.

> So I'm wondering if we're carrying all this extra DMA complexity
> and workarounds for just am335x?
> 

Sebastian

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Re: [PATCH] tty: serial: 8250_omap: do not defer termios changes Peter Hurley <peter@hurleysoftware.com> - 2016-04-05 06:10 +0200
  Re: [PATCH] tty: serial: 8250_omap: do not defer termios changes John Ogness <john.ogness@linutronix.de> - 2016-04-11 10:20 +0200
    Re: [PATCH] tty: serial: 8250_omap: do not defer termios changes Peter Hurley <peter@hurleysoftware.com> - 2016-04-11 20:00 +0200
      Re: [PATCH] tty: serial: 8250_omap: do not defer termios changes Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2016-04-11 20:40 +0200
        Re: [PATCH] tty: serial: 8250_omap: do not defer termios changes Peter Hurley <peter@hurleysoftware.com> - 2016-04-11 22:20 +0200
          Re: [PATCH] tty: serial: 8250_omap: do not defer termios changes Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2016-04-12 19:10 +0200
            Re: [PATCH] tty: serial: 8250_omap: do not defer termios changes Peter Hurley <peter@hurleysoftware.com> - 2016-04-12 20:50 +0200
              Re: [PATCH] tty: serial: 8250_omap: do not defer termios changes Peter Hurley <peter@hurleysoftware.com> - 2016-04-14 18:10 +0200
            8250 dma issues ( was Re: [PATCH] tty: serial: 8250_omap: do not  defer termios changes) Peter Hurley <peter@hurleysoftware.com> - 2016-04-13 01:30 +0200
              Re: 8250 dma issues ( was Re: [PATCH] tty: serial: 8250_omap: do  not defer termios changes) One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-04-14 17:10 +0200
                Re: 8250 dma issues ( was Re: [PATCH] tty: serial: 8250_omap: do not  defer termios changes) Peter Hurley <peter@hurleysoftware.com> - 2016-04-14 20:00 +0200
            omap uart + dma issues (Re: [PATCH] tty: serial: 8250_omap: do not  defer termios changes) Peter Hurley <peter@hurleysoftware.com> - 2016-04-13 02:10 +0200
              Re: omap uart + dma issues (Re: [PATCH] tty: serial: 8250_omap: do  not defer termios changes) Sekhar Nori <nsekhar@ti.com> - 2016-04-13 13:20 +0200
                Re: omap uart + dma issues (Re: [PATCH] tty: serial: 8250_omap: do  not defer termios changes) Peter Hurley <peter@hurleysoftware.com> - 2016-04-14 03:20 +0200

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