Date:   Mon, 27 Apr 2020 10:56:08 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        linux-amlogic@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-mmc@...r.kernel.org, ulf.hansson@...aro.org,
        robh+dt@...nel.org
Cc:     mark.rutland@....com, jianxin.pan@...ogic.com,
        linux-kernel@...r.kernel.org, yinxin_1989@...yun.com,
        linux-arm-kernel@...ts.infradead.org, lnykww@...il.com
Subject: Re: [PATCH v5 0/3] Amlogic 32-bit Meson SoC SDHC MMC controller driver


On Sat 28 Mar 2020 at 01:32, Martin Blumenstingl <martin.blumenstingl@...glemail.com> wrote:

> Hello,
>
> this is the patchset for a driver for the Amlogic "SDHC" MMC controller
> found on Meson6, Meson8, Meson8b and Meson8m2 SoCs.
>
> The public S805 (Meson8b) datasheet has some documentation starting on
> page 74: [0]
>
> It's performance is still not as good as the driver from Amlogic's 3.10
> kernel, but it does not corrupt data anymore (as RFC v1 did).
>
> Special thanks to the people who supported me off-list - you are
> amazing and deserve to be mentioned here:
> - Xin Yin who helped me fix two more write corruption problems. I am
>   hoping that he will reply with Reviewed-by, Tested-by and Bug-fixed-by
> - Jianxin Pan for sharing some of the internal workings of this MMC
>   controller with me
> - Wei Wang for spotting the initial write corruption problem and helping
>   test this driver on his board. I have his permission to add his
>   Tested-by (off-list, he's Cc'ed so if there's any problem he can speak
>   up)
>
>
> Changes since v4 at [4]:
> - move the four clkin clock inputs to the start of the clock-names list
>   as suggested by Rob, affects patch #1
> - fixed #include statement in dt-bindings example in patch #1
>
> Changes since v3 at [3]:
> - split the clock bits into a separate clock controller driver because
>   of two reasons: 1) it keeps the MMC controller driver mostly clean of
>   the clock bits

If the register is in the MMC controller register space and the MMC
driver is the driver using these clocks, it is where the clocks belong.
I don't get why it could be an issue ?

Is the clock block is shared with another device, like on the Gx family ?

> 2) the pure clock controller can use
>   devm_clk_hw_register() (instead of devm_clk_register(), which is
>   deprecated) and the MMC controller can act as a pure clock consumer.

Why can't you use devm_clk_hw_register in an MMC driver ?
Unless I missed something, it is provided by clk-provider.h, which can be
included by any driver.

I'm not sure I understand why the support for this device is split in
two drivers. Using CCF clocks out of "drivers/clk" is encouraged.

>   This also affects the dt-bindings which is why I dropped Rob's
>   Reviewed-by. Thanks to Ulf for the suggestions
>
> Changes since v2 at [2]:
> - rebased on top of v5.5-rc1
> - added Rob's and Xin Yin's Reviewed-by and Tested-by (thank you!)
> - (note: Kevin had v2 of this series in -next for a few days so the
>    build test robots could play with it. I haven't received any negative
>    feedback in that time)
>
> Changes since RFC v1 at [1]:
> - don't set MESON_SDHC_MISC_MANUAL_STOP to fix one of three write
>   corruption problems. the out-of-tree 3.10 "reference" driver doesn't
>   set it either
> - check against data->flags instead of cmd->flags when testing for
>   MMC_DATA_WRITE as spotted by Xin Yin (many thanks!). This fixes
>   another write corruption problem
> - clear the FIFOs after successfully transferring data as suggested by
>   Xin Yin (many thanks!). This is what the 3.10 driver did and fixes yet
>   another write corruption problem
> - integrate the clock suggestions from Jianxin Pan so the driver is now
>   able to set up the clocks correctly for all known cases. documentation
>   is also added to the patch description. Thank you Jianxin for the
>   help!
> - set the correct max_busy_timeout as suggested by Jianxin Pan (thanks!)
> - convert the dt-bindings to .yaml (which is why I didn't add Rob's
>   Reviewed-by)
> - switch to struct clk_parent_data as part of newer common clock
>   framework APIs to simplify the clock setup
> - dropped CMD23 support because it seems to hurt read and write
>   performance by 10-20% in my tests. it's not clear why, but for now we
>   can live without this.
> - use devm_platform_ioremap_resource instead of open-coding it
>
>
> [0] https://dn.odroid.com/S805/Datasheet/S805_Datasheet%20V0.8%2020150126.pdf
> [1] https://patchwork.kernel.org/cover/11035505/
> [2] http://lists.infradead.org/pipermail/linux-amlogic/2019-November/014576.html
> [3] https://patchwork.kernel.org/cover/11283179/
> [4] https://patchwork.kernel.org/cover/11329017/
>
> Martin Blumenstingl (3):
>   dt-bindings: mmc: Document the Amlogic Meson SDHC MMC host controller
>   clk: meson: add a driver for the Meson8/8b/8m2 SDHC clock controller
>   mmc: host: meson-mx-sdhc: new driver for the Amlogic Meson SDHC host
>
>  .../bindings/mmc/amlogic,meson-mx-sdhc.yaml   |   83 ++
>  drivers/clk/meson/Kconfig                     |    9 +
>  drivers/clk/meson/Makefile                    |    1 +
>  drivers/clk/meson/meson-mx-sdhc.c             |  212 ++++
>  drivers/mmc/host/Kconfig                      |   14 +
>  drivers/mmc/host/Makefile                     |    1 +
>  drivers/mmc/host/meson-mx-sdhc.c              | 1064 +++++++++++++++++
>  .../dt-bindings/clock/meson-mx-sdhc-clkc.h    |    8 +
>  8 files changed, 1392 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mmc/amlogic,meson-mx-sdhc.yaml
>  create mode 100644 drivers/clk/meson/meson-mx-sdhc.c
>  create mode 100644 drivers/mmc/host/meson-mx-sdhc.c
>  create mode 100644 include/dt-bindings/clock/meson-mx-sdhc-clkc.h

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