linux-kernel - Re: [PATCH] Revert "serial: 8250: Fix clearing FIFOs in RS485 mode again"

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Date:   Fri, 21 Dec 2018 21:08:28 +0100
From:   Marek Vasut <marex@...x.de>
To:     Paul Burton <paul.burton@...s.com>
Cc:     "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Paul Burton <pburton@...ecomp.com>,
        Daniel Jedrychowski <avistel@...il.com>,
        "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
        stable <stable@...r.kernel.org>,
        Ezequiel Garcia <ezequiel@...labora.com>
Subject: Re: [PATCH] Revert "serial: 8250: Fix clearing FIFOs in RS485 mode
 again"

On 12/16/2018 11:28 PM, Paul Burton wrote:
> Hi Marek,
> 
> On Sun, Dec 16, 2018 at 11:01:18PM +0100, Marek Vasut wrote:
>>>>> I did suggest an alternative approach which would rename
>>>>> serial8250_clear_fifos() and split it into 2 variants - one that
>>>>> disables FIFOs & one that does not, then use the latter in
>>>>> __do_stop_tx_rs485():
>>>>>
>>>>> https://lore.kernel.org/lkml/20181213014805.77u5dzydo23cm6fq@pburton-laptop/
>>>>>
>>>>> However I have no access to the OMAP3 hardware that Marek's patch was
>>>>> attempting to fix & have heard nothing back with regards to him testing
>>>>> that approach, so here's a simple revert that fixes the Ingenic JZ4780.
>>>>>
>>>>> I've marked for stable back to v4.10 presuming that this is how far the
>>>>> broken patch may be backported, given that this is where commit
>>>>> 2bed8a8e7072 ("Clearing FIFOs in RS485 emulation mode causes subsequent
>>>>> transmits to break") that it tried to fix was introduced.
>>>>
>>>> OK, I tested this on AM335x / OMAP3 and the system is again broken, so
>>>> that's a NAK.
>>>
>>> To be clear - what did you test? This revert or the patch linked to
>>> above?
>>>
>>> This revert would of course reintroduce your RS485 issue because it just
>>> undoes your change.
>>
>> The revert. Which of the two patches do you need me to test.
> 
> The one in the email I sent on Thursday 13th at 01:48:06 UTC, linked to
> at lore.kernel.org in the quote right above:
> 
> https://lore.kernel.org/lkml/20181213014805.77u5dzydo23cm6fq@pburton-laptop/
> 
> You replied with comments on the patch, you just never tested it or
> never told me if you did. The lack of response means I don't know
> whether that potential patch even still works for your system, hence the
> revert.

I shared the entire testcase, which now fails on AM335x due to this
revert. Is there any progress on a proper fix from your side which does
not break the AM335x ?

-- 
Best regards,
Marek Vasut