linux-kernel - Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm

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Message-ID: <YP/iSZpJ5AIJV70Z@atomide.com>
Date:   Tue, 27 Jul 2021 13:39:05 +0300
From:   Tony Lindgren <tony@...mide.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Vignesh Raghavendra <vigneshr@...com>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
        Linux ARM Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] serial: 8250: 8250_omap: Fix possible interrupt storm

* Andy Shevchenko <andy.shevchenko@...il.com> [210713 09:14]:
> On Tue, Jul 13, 2021 at 11:54 AM Vignesh Raghavendra <vigneshr@...com> wrote:
> > On 7/13/21 1:57 AM, andy@...facebook.localdomain wrote:
> > > Tue, Jun 22, 2021 at 11:53:38AM +0530, Vignesh Raghavendra kirjoitti:
> 
> ...
> 
> > > https://lore.kernel.org/linux-serial/20170206233000.3021-1-dianders@chromium.org/
> >
> > I am not sure if reading UART_LSR is a good idea in the above patch.
> > Some flags in LSR register are cleared on read (at least that's the case
> > for UARTs on TI SoCs) and thus can result in loss of error/FIFO status
> > information.
> >
> > > https://lore.kernel.org/linux-serial/1440015124-28393-1-git-send-email-california.l.sullivan@intel.com/
> >
> > Looks like this never made it.
> 
> Forgot to react to the above. Yes, they never made it because I
> believe due to the exact reason you mentioned above. Also California
> set up different experiments IIRC and it shows that the problem didn;t
> fully disappear with his approach. But maybe yours will work better
> (at least it's not the first time I have seen it on different hardware
> according to people's contributions).

Not sure if this is the same issue with noisy lines, but see also the
following in case it's related:

[PATCH 2/2] serial: 8250_omap: Handle optional overrun-throttle-ms property

Also available at [0] below.

Regards,

Tony

[0] https://lore.kernel.org/linux-omap/20210727103533.51547-1-tony@atomide.com/T/#m5f9da26c32503f2937d3d5977310ca337fa0cb5a