linux-kernel - Re: [PATCH 2/3] aspeed-video: clear spurious interrupt bits unconditionally

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Date:   Tue, 22 Dec 2020 13:14:33 -0600
From:   Zev Weiss <zev@...ilderbeest.net>
To:     Joel Stanley <joel@....id.au>
Cc:     Eddie James <eajames@...ux.ibm.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Andrew Jeffery <andrew@...id.au>, linux-media@...r.kernel.org,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-aspeed <linux-aspeed@...ts.ozlabs.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jae Hyun Yoo <jae.hyun.yoo@...ux.intel.com>
Subject: Re: [PATCH 2/3] aspeed-video: clear spurious interrupt bits
 unconditionally

On Mon, Dec 21, 2020 at 10:47:37PM CST, Joel Stanley wrote:
>On Tue, 15 Dec 2020 at 02:46, Zev Weiss <zev@...ilderbeest.net> wrote:
>>
>> Instead of testing and conditionally clearing them one by one, we can
>> instead just unconditionally clear them all at once.
>>
>> Signed-off-by: Zev Weiss <zev@...ilderbeest.net>
>
>I had a poke at the assembly and it looks like GCC is clearing the
>bits unconditionally anyway, so removing the tests provides no change.
>
>Combining them is a good further optimization.
>
>Reviewed-by: Joel Stanley <joel@....id.au>
>
>A question unrelated to this patch: Do you know why the driver doesn't
>clear the status bits in the interrupt handler? I would expect it to
>write the value of sts back to the register to ack the pending
>interrupt.
>

No, I don't, and I was sort of wondering the same thing actually -- I'm 
not deeply familiar with this hardware or driver though, so I was a bit 
hesitant to start messing with things.  (Though maybe doing so would 
address the "stickiness" aspect when it does manifest.)  Perhaps Eddie 
or Jae can shed some light here?


Zev