linux-kernel - Re: [PATCH v5 0/2] clk: fractional-divider: Improve approximation when zero based and export

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Message-ID: <874jm3lzce.fsf@oltmanns.dev>
Date:   Mon, 17 Jul 2023 10:24:49 +0200
From:   Frank Oltmanns <frank@...manns.dev>
To:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     "A.s. Dong" <aisheng.dong@....com>,
        Abel Vesa <abelvesa@...nel.org>,
        Fabio Estevam <festevam@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, NXP Linux Team <linux-imx@....com>,
        Peng Fan <peng.fan@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>,
        Elaine Zhang <zhangqing@...k-chips.com>
Subject: Re: [PATCH v5 0/2] clk: fractional-divider: Improve approximation
 when zero based and export

Hi,

On 2023-06-17 at 15:10:39 +0200, Frank Oltmanns <frank@...manns.dev> wrote:
> The fractional divider approximation does not utilize the full available
> range for clocks that are flagged CLK_FRAC_DIVIDER_ZERO_BASED. This
> patchset aims to fix that.
>
> It also adds test cases for the edge cases of fractional divider clocks
> with and without the CLK_FRAC_DIVIDER_ZERO_BASED flag to highlight the
> changes.
>
> Finally, it also exports clk_fractional_divider_general_approximation so
> that the test cases (but also other users like rockchip clk driver) can
> be compiled as a module.
>
> Unfortunately, I have no boards to test this patch. So all we have are
> the unit tests. It seems the only user of this flag in mainline is
> drivers/clk/imx/clk-composite-7ulp.c, therefore I'm cc-ing
> get_maintainers.pl --git-blame -f drivers/clk/imx/clk-composite-7ulp.c
> in the hopes of a wider audience.

Are there remarks or questions on this patchset? Anything that needs to
be improved?

Thanks,
  Frank

>
> Thank you for considering this contribution,
>   Frank
>
> P.S.: V4 was short-lived, because it triggered a compiler warning on
> clang. I'm sorry for the noise. -- Frank
>
> V4: https://lore.kernel.org/all/20230617102919.27564-1-frank@oltmanns.dev/
> V3: https://lore.kernel.org/all/20230614185521.477924-1-frank@oltmanns.dev/
> V2: https://lore.kernel.org/lkml/20230613083626.227476-1-frank@oltmanns.dev/
> V1: https://lore.kernel.org/lkml/20230529133433.56215-1-frank@oltmanns.dev/
>
> Changes in V5 (since V4):
>  - Fix compiler warnings on clang by removing superfluous variable max_m
>    in the test cases for the maximum denominator (n) and max_n in the
>    test cases for max numerator (m).
>    Thank you, Intel, for your kernel test robot!
>
> Changes in V4 (since V3):
>  - Export clk_fractional_divider_general_approximation so that users
>    (e.g., the testcases) can be compiled as modules.
>  - Change test cases so that they test
>    clk_fractional_divider_general_approximation again (like in V2)
>    instead of clk_fd_round_rate (like in V3), but keeping the structure
>    of V3 with separate file and individual test cases for each edge
>    case.
>
> Changes in V3 (since V2):
>  - Completely reworked the test cases
>    - Moved tests to separate file as per Stephen's request
>    - Move each edge case into their individual test case as per
>      Stephen's request
>    - Test clk_fd_round_rate instead of
>      clk_fractional_divider_general_approximation as testing the latter
>      broke builds
>
> Changes in V2 (since V1):
>  - Added test case as requested by Stephen Boyd
>  - Fixed commit message as the Cc: was missing a closing bracket, so that the
>    original mail unfortunately did not go out to A. s. Dong.
>
> Frank Oltmanns (2):
>   clk: fractional-divider: Improve approximation when zero based and
>     export
>   clk: fractional-divider: tests: Add test suite for edge cases
>
>  drivers/clk/.kunitconfig                  |   1 +
>  drivers/clk/Kconfig                       |   7 +
>  drivers/clk/Makefile                      |   1 +
>  drivers/clk/clk-fractional-divider.c      |  27 +++-
>  drivers/clk/clk-fractional-divider_test.c | 157 ++++++++++++++++++++++
>  5 files changed, 186 insertions(+), 7 deletions(-)
>  create mode 100644 drivers/clk/clk-fractional-divider_test.c