linux-kernel - Re: [PATCH v2 2/3] dt-bindings: mmc: Add a new property disable-cqe-dcmd.

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Message-Id: <3BCC2A27-3AF4-4E5E-BBD4-6A5B49831D3C@theobroma-systems.com>
Date:   Fri, 8 Mar 2019 14:10:45 +0100
From:   Christoph Müllner 
        <christoph.muellner@...obroma-systems.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     robh+dt@...nel.org, mark.rutland@....com,
        Heiko Stuebner <heiko@...ech.de>, shawn.lin@...k-chips.com,
        ulf.hansson@...aro.org,
        Philipp Tomsich <philipp.tomsich@...obroma-systems.com>,
        Michal Simek <michal.simek@...inx.com>,
        Douglas Anderson <dianders@...omium.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Vicente Bergas <vicencb@...il.com>,
        Emil Renner Berthing <kernel@...il.dk>,
        Randy Li <ayaka@...lik.info>,
        Tony Xie <tony.xie@...k-chips.com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Klaus Goger <klaus.goger@...obroma-systems.com>,
        Lin Huang <hl@...k-chips.com>, linux-mmc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v2 2/3] dt-bindings: mmc: Add a new property
 disable-cqe-dcmd.


> On 08.03.2019, at 13:46, Adrian Hunter <adrian.hunter@...el.com> wrote:
> 
> On 7/03/19 10:43 AM, Christoph Muellner wrote:
>> This patch documents the new property disable-cqe-dcmd
>> for the Arasan eMMC 5.1 driver.
>> 
>> Signed-off-by: Christoph Muellner <christoph.muellner@...obroma-systems.com>
>> Signed-off-by: Philipp Tomsich <philipp.tomsich@...obroma-systems.com>
>> ---
>> Documentation/devicetree/bindings/mmc/arasan,sdhci.txt | 4 ++++
>> 1 file changed, 4 insertions(+)
>> 
>> diff --git a/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt b/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
>> index 1edbb049cccb..ec699bf98b7c 100644
>> --- a/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
>> +++ b/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
>> @@ -44,6 +44,10 @@ Optional Properties:
>>     properly. Test mode can be used to force the controller to function.
>>   - xlnx,int-clock-stable-broken: when present, the controller always reports
>>     that the internal clock is stable even when it is not.
>> +  - disable-cqe-dcmd: The eMMC 5.1 standard specifies direct commands (DCMDs)
>> +    as part of the command queue engine (CQE). On controllers with a CQHCI,
>> +    such as the Arasan eMMC 5.1 host controller, the driver has to enable DCMDs.
>> +    This is done unless disable-cqe-dcmd is specified.
> 
> If "supports-cqe" is in mmc.txt, should "disable-cqe-dcmd" be there also?

The file mmc.txt says on top:
"These properties are common to multiple MMC host controllers".
As my patchset introduces "disable-cqe-dcmd" just for sdhci-of-arasan,
I would say it should not go into that file.

Also I wonder why "supports-cqe" is in mmc.txt, because
only sdhci-tegra.c is evaluating that property.
So I would expect it to be documented in
Documentation/devicetree/bindings/mmc/nvidia,tegra20-sdhci.txt

However, I see that "disable-cqe-dcmd" could go into other drivers as well.
But is this enough to document it in mmc.txt?