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

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Date:   Sun, 16 Dec 2018 22:28:17 +0000
From:   Paul Burton <paul.burton@...s.com>
To:     Marek Vasut <marex@...x.de>
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>
Subject: Re: [PATCH] Revert "serial: 8250: Fix clearing FIFOs in RS485 mode
 again"

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.

Thanks,
    Paul