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

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Message-ID: <CAHCN7xJpa68bB+acaywq+ca0sG0gYXM2wBiK=50KWLVp6e-9FA@mail.gmail.com>
Date:   Thu, 28 Nov 2019 08:28:49 -0600
From:   Adam Ford <aford173@...il.com>
To:     Jacopo Mondi <jacopo@...ndi.org>
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

On Thu, Nov 28, 2019 at 4:19 AM Jacopo Mondi <jacopo@...ndi.org> wrote:
>
> 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

That makes sense.

I'll do a V2 for this patch and change the description and add your
'acked-by' note to it.

I probably won't get to it until this weekend, since today is a
holiday in the US, and I am traveling.

adam
>
> > >
> > > 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
> > >