From: Wolfram Sang <wsa+renesas@sang-engineering.com>
To: Biju Das <biju.das.jz@bp.renesas.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>,
linux-mmc@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: Sat, 24 Sep 2022 12:18:24 +0200 [thread overview]
Message-ID: <Yy7ZcJ8h2VCtUDnW@shikoro> (raw)
In-Reply-To: <20220922085511.1078256-1-biju.das.jz@bp.renesas.com>
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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?)
> + * 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?
Happy hacking,
Wolfram
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next prev parent reply other threads:[~2022-09-24 10:18 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 [this message]
2022-09-25 17:06 ` Biju Das
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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