linux-kernel - AW: [PATCH] gpu: ipu-v3: Fix dev

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Date:   Fri, 25 Mar 2022 18:01:50 +0000
From:   "Jonas Mark (BT-FIR/ENG1-Grb)" <Mark.Jonas@...bosch.com>
To:     Philipp Zabel <p.zabel@...gutronix.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
CC:     "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "RUAN Tingquan (BT-FIR/ENG1-Zhu)" <Tingquan.Ruan@...bosch.com>,
        "Jonas Mark (BT-FIR/ENG1-Grb)" <Mark.Jonas@...bosch.com>
Subject: AW: [PATCH] gpu: ipu-v3: Fix dev_dbg frequency output

Hi,

> > This commit corrects the printing of the IPU clock error percentage if
> > it is between -0.1% to -0.9%. For example, if the pixel clock
> > requested is 27.2 MHz but only 27.0 MHz can be achieved the deviation is -
> 0.8%.
> > But the fixed point math had a flaw and calculated error of 0.2%.
> >
> > Before:
> >   Clocks: IPU 270000000Hz DI 24716667Hz Needed 27200000Hz
> >   IPU clock can give 27000000 with divider 10, error 0.2%
> >   Want 27200000Hz IPU 270000000Hz DI 24716667Hz using IPU,
> 27000000Hz
> >
> > After:
> >   Clocks: IPU 270000000Hz DI 24716667Hz Needed 27200000Hz
> >   IPU clock can give 27000000 with divider 10, error -0.8%
> >   Want 27200000Hz IPU 270000000Hz DI 24716667Hz using IPU,
> 27000000Hz
> >
> > Signed-off-by: Leo Ruan <tingquan.ruan@...bosch.com>
> > Signed-off-by: Mark Jonas <mark.jonas@...bosch.com>
> > ---
> >  drivers/gpu/ipu-v3/ipu-di.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/ipu-v3/ipu-di.c b/drivers/gpu/ipu-v3/ipu-di.c
> > index b4a31d506fcc..74eca68891ad 100644
> > --- a/drivers/gpu/ipu-v3/ipu-di.c
> > +++ b/drivers/gpu/ipu-v3/ipu-di.c
> > @@ -451,8 +451,9 @@ static void ipu_di_config_clock(struct ipu_di *di,
> >
> >                 error = rate / (sig->mode.pixelclock / 1000);
> >
> > -               dev_dbg(di->ipu->dev, "  IPU clock can give %lu with
> > divider %u, error %d.%u%%\n",
> > -                       rate, div, (signed)(error - 1000) / 10, error
> > % 10);
> > +               dev_dbg(di->ipu->dev, "  IPU clock can give %lu with
> > +divider %u, error %c%d.%d%%\n",
> > +                       rate, div, error < 1000 ? '-' : '+',
> > +                       abs(error - 1000) / 10, abs(error - 1000) %
> > +10);
> >
> >                 /* Allow a 1% error */
> >                 if (error < 1010 && error >= 990) {
> 
> Rounding (always down) is still a bit unintuitive, but this certainly improves
> things.
> 
> Reviewed-by: Philipp Zabel <p.zabel@...gutronix.de>

What are the chances of getting this patch into 5.18?

Can I do something to support the process?

Cheers,
Mark