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

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Message-ID: <CAHp75Vcxtk0f2KRSL8gh2mz-AYE7Kav6co8N8XMbsvtyLohG5w@mail.gmail.com>
Date:   Tue, 13 Jul 2021 12:13:23 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Vignesh Raghavendra <vigneshr@...com>
Cc:     "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Tony Lindgren <tony@...mide.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

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).

-- 
With Best Regards,
Andy Shevchenko