Re: [V2] tty: serial: qcom-geni-serial: Fix get_clk_div_rate() which otherwise could return a sub-optimal clock rate.

[Doug Anderson]

Hi,

On Thu, Jun 30, 2022 at 10:19 AM Vijaya Krishna Nivarthi (Temp) (QUIC)
<quic_vnivarth@xxxxxxxxxxx> wrote:
>
> > -----Original Message-----
> > From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
> > Sent: Thursday, June 30, 2022 8:31 PM
> > To: Vijaya Krishna Nivarthi (Temp) (QUIC) <quic_vnivarth@xxxxxxxxxxx>
> > Cc: agross@xxxxxxxxxx; bjorn.andersson@xxxxxxxxxx;
> > konrad.dybcio@xxxxxxxxxxxxxx; jirislaby@xxxxxxxxxx; linux-arm-
> > msm@xxxxxxxxxxxxxxx; linux-serial@xxxxxxxxxxxxxxx; linux-
> > kernel@xxxxxxxxxxxxxxx; Mukesh Savaliya (QUIC)
> > <quic_msavaliy@xxxxxxxxxxx>; dianders@xxxxxxxxxxxx;
> > mka@xxxxxxxxxxxx; swboyd@xxxxxxxxxxxx
> > Subject: Re: [V2] tty: serial: qcom-geni-serial: Fix get_clk_div_rate() which
> > otherwise could return a sub-optimal clock rate.
> >
> > WARNING: This email originated from outside of Qualcomm. Please be wary
> > of any links or attachments, and do not enable macros.
> >
> > On Wed, Jun 29, 2022 at 03:30:41PM +0530, Vijaya Krishna Nivarthi wrote:
> > > In the logic around call to clk_round_rate(), for some corner
> > > conditions,
> > > get_clk_div_rate() could return an sub-optimal clock rate. Also, if an
> > > exact clock rate was not found lowest clock was being returned.
> > >
> > > Search for suitable clock rate in 2 steps
> > > a) exact match or within 2% tolerance
> > > b) within 5% tolerance
> > > This also takes care of corner conditions.
> > >
> > > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> >
> > Did the test robot really report the original issue, or just the v2 change?
> >
> > thanks,
> >
> > greg k-h
>
> Test robot raised error for v1 patch and (I think) it got addressed in v2 with call to div_u64.
> V2 doesn't have this error but other warnings which I am addressing along with other feedback.
> Below is the error raised for v1.

I think the adding of the "Reported-by" only really makes sense if the
commit landed and then you fixed the robot-reported bug in a separate
commit. If it reported problems in v1 and you fix them in v2 you
shouldn't add the tag.

-Doug