linux-kernel - Re: [PATCH] media: ov5640: Fix check for PLL1 exceeding max allowed rate

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Message-ID: <20191128102141.beq7wzdu5vxwx7wk@uno.localdomain>
Date:   Thu, 28 Nov 2019 11:21:41 +0100
From:   Jacopo Mondi <jacopo@...ndi.org>
To:     Adam Ford <aford173@...il.com>
Cc:     linux-media <linux-media@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Steve Longerbeam <slongerbeam@...il.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Adam Ford <adam.ford@...icpd.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] media: ov5640: Fix check for PLL1 exceeding max allowed
 rate

Hi Adam,

On Tue, Nov 26, 2019 at 08:08:05PM -0600, Adam Ford wrote:
> On Tue, Oct 29, 2019 at 7:42 AM Adam Ford <aford173@...il.com> wrote:
> >
> > The variable _rate is by ov5640_compute_sys_clk() which returns
> > zero if the PLL exceeds 1GHz.  Unfortunately, the check to see
> > if the max PLL1 output is checking 'rate' and not '_rate' and
> > 'rate' does not ever appear to be 0.

This seems a bit convoluted. What about:

"The PLL calculation routine checks the wrong variable 'rate' to
verify that the calculated PLL1 output frequency does not exceed
1GHz. Fix this by using the correct '_rate' one."

Or something against these lines

> >
> > This patch changes the check against the returned value of
> > '_rate' to determine if the PLL1 output exceeds 1GHz.
> >
> > Fixes: aa2882481cad ("media: ov5640: Adjust the clock based on the expected rate")
> >
>
> I haven't seen any responses to this patch.  Has anyone had a chance
> to review this?  It's been nearly a month.

You're totally right! Sorry about this

> I think it would be appropriate to backport to stable if deemed acceptable.
>

Indeed! This fixes a real issue

Acked-by: Jacopo Mondi <jacopo@...ndi.org>

Thanks
  j

> adam
>
> > Signed-off-by: Adam Ford <aford173@...il.com>
> >
> > diff --git a/drivers/media/i2c/ov5640.c b/drivers/media/i2c/ov5640.c
> > index 5e495c833d32..bb968e764f31 100644
> > --- a/drivers/media/i2c/ov5640.c
> > +++ b/drivers/media/i2c/ov5640.c
> > @@ -874,7 +874,7 @@ static unsigned long ov5640_calc_sys_clk(struct ov5640_dev *sensor,
> >                          * We have reached the maximum allowed PLL1 output,
> >                          * increase sysdiv.
> >                          */
> > -                       if (!rate)
> > +                       if (!_rate)
> >                                 break;
> >
> >                         /*
> > --
> > 2.17.1
> >

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