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Message-ID: <20240729093259.GB2320@pendragon.ideasonboard.com>
Date: Mon, 29 Jul 2024 12:32:59 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Matthias Fend <matthias.fend@...end.at>
Cc: Rui Miguel Silva <rmfrfs@...il.com>,
Martin Kepplinger <martink@...teo.de>,
Purism Kernel Team <kernel@...i.sm>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Shawn Guo <shawnguo@...nel.org>,
Sascha Hauer <s.hauer@...gutronix.de>,
Pengutronix Kernel Team <kernel@...gutronix.de>,
Fabio Estevam <festevam@...il.com>, linux-media@...r.kernel.org,
imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: imx-mipi-csis: avoid logging while holding
spinlock
On Fri, Jul 26, 2024 at 02:16:07PM +0200, Matthias Fend wrote:
> Hi Laurent,
>
> Am 26.07.2024 um 12:42 schrieb Laurent Pinchart:
> > Hi Matthias,
> >
> > Thank you for the patch.
> >
> > On Tue, Jul 23, 2024 at 08:09:08AM +0200, Matthias Fend wrote:
> >> Refactor mipi_csis_log_counters() to prevent calling dev_info() while
> >> IRQs are disabled. This reduces crucial IRQs off time to a bare minimum.
> >
> > Should we add
> >
> > Cc: stable@...r.kernel.org
> >
> > to get this backported to stable kernels ?
>
> Hard for me to tell. Since this problem only occurs when you explicitly
> trigger the debug output from this driver, it probably only affects very
> few end users. So I'm not sure if a backport would be worth it.
I slept over it and decided not to Cc stable.
> >> Signed-off-by: Matthias Fend <matthias.fend@...end.at>
> >> ---
> >> drivers/media/platform/nxp/imx-mipi-csis.c | 9 ++++++---
> >> 1 file changed, 6 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/media/platform/nxp/imx-mipi-csis.c b/drivers/media/platform/nxp/imx-mipi-csis.c
> >> index f49b06978f14..0c34d316ed29 100644
> >> --- a/drivers/media/platform/nxp/imx-mipi-csis.c
> >> +++ b/drivers/media/platform/nxp/imx-mipi-csis.c
> >> @@ -857,18 +857,21 @@ static void mipi_csis_log_counters(struct mipi_csis_device *csis, bool non_error
> >> {
> >> unsigned int num_events = non_errors ? MIPI_CSIS_NUM_EVENTS
> >> : MIPI_CSIS_NUM_EVENTS - 8;
> >> + unsigned int counters[MIPI_CSIS_NUM_EVENTS];
> >> unsigned long flags;
> >> unsigned int i;
> >>
> >> spin_lock_irqsave(&csis->slock, flags);
> >> + for (i = 0; i < num_events; ++i)
> >> + counters[i] = csis->events[i].counter;
> >> + spin_unlock_irqrestore(&csis->slock, flags);
> >>
> >> for (i = 0; i < num_events; ++i) {
> >> - if (csis->events[i].counter > 0 || csis->debug.enable)
> >> + if (counters[i] > 0 || csis->debug.enable)
> >> dev_info(csis->dev, "%s events: %d\n",
> >> csis->events[i].name,
> >> - csis->events[i].counter);
> >> + counters[i]);
> >
> > The last two lines now fit in a single line. No need for a v2, I'll
> > rewrap the code myself, and add the Cc line if you think that's a good
> > idea.
>
> Thanks! Regarding Cc, I would like to leave it up to you; you have the
> necessary experience and overview to judge that.
>
> ~Matthias
>
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> >
> >> }
> >> - spin_unlock_irqrestore(&csis->slock, flags);
> >> }
> >>
> >> static int mipi_csis_dump_regs(struct mipi_csis_device *csis)
--
Regards,
Laurent Pinchart
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