From: Biju Das <biju.das.jz@bp.renesas.com>
To: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>,
"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
"linux-renesas-soc@vger.kernel.org"
<linux-renesas-soc@vger.kernel.org>,
Geert Uytterhoeven <geert+renesas@glider.be>,
Chris Paterson <Chris.Paterson2@renesas.com>,
Biju Das <biju.das@bp.renesas.com>,
Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>
Subject: RE: [PATCH v3] mmc: renesas_sdhi: Fix rounding errors
Date: Sun, 25 Sep 2022 17:06:39 +0000 [thread overview]
Message-ID: <TYCPR01MB5933319E9510B176644D2BC986539@TYCPR01MB5933.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <Yy7ZcJ8h2VCtUDnW@shikoro>
Hi Wolfram,
Thanks for the feedback.
> Subject: Re: [PATCH v3] mmc: renesas_sdhi: Fix rounding errors
>
> Hi,
>
> > v2->v3:
> > * Renamed the variable new_clock_margin->new_upper_limit in
> renesas_sdhi_clk_
> > update()
> > * Moved setting of new_upper_limit outside for loop.
> > * Updated the comment section to mention the rounding errors and
> merged with
> > existing comment out side the for loop.
> > * Updated commit description.
>
> I really like the new variable names.
>
> > + * To fix rounding errors, eg:- (533333333 Hz / 4 * 4 = 533333332
> Hz
> > +<
>
> (What is the '-' after 'eg:' for?)
Regarding 'eg:-', I got this habit from school days. On exams, I usually
write for eg:- to provide some examples.
OK, Will remove '-' after 'eg:'.
>
> > + * 533333333 Hz) add an upper limit of 1/1024 rate higher to the
> clock
> > + * rate.
>
> I know Geert suggesgted this. I think, however, this description is
> too short. It should be mentioned IMHO that this rounding error can
> lead to the selection of a clock which is way off (the 400MHz one). I
> liked this example from v2. Geert, what do you say?
Yes, I can put back the real example from v2, if that is useful.
533MHz->400 MHz is a big jump due to this rounding error and it has
impacted the performance.
Waiting for Geert's feedback.
Cheers,
Biju
next prev parent reply other threads:[~2022-09-25 17:06 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-22 8:55 [PATCH v3] mmc: renesas_sdhi: Fix rounding errors Biju Das
2022-09-24 10:18 ` Wolfram Sang
2022-09-25 17:06 ` Biju Das [this message]
2022-09-26 12:20 ` Geert Uytterhoeven
2022-09-26 12:52 ` Biju Das
2022-09-25 16:51 ` Wolfram Sang
2022-09-26 17:13 ` Biju Das
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