linux-kernel - Re: [PATCH 1/2] Documentation: phy: introduce new optional property to specify drive impedance

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Date:   Fri, 6 Jan 2017 08:44:09 +0800
From:   Shawn Lin <shawn.lin@...k-chips.com>
To:     Heiko Stübner <heiko@...ech.de>
Cc:     shawn.lin@...k-chips.com, Kishon Vijay Abraham I <kishon@...com>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-rockchip@...ts.infradead.org,
        Douglas Anderson <dianders@...omium.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] Documentation: phy: introduce new optional property
 to specify drive impedance

On 2017/1/5 19:15, Heiko Stübner wrote:
> Hi Shawn,
>
> Am Donnerstag, 5. Januar 2017, 17:31:21 schrieb Shawn Lin:
>> We need to modify the drive impedance according to the
>> different hardware condition. So let's expose this to
>> the DT.
>>
>> Signed-off-by: Shawn Lin <shawn.lin@...k-chips.com>
>> ---
>>
>>  Documentation/devicetree/bindings/phy/rockchip-emmc-phy.txt | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/phy/rockchip-emmc-phy.txt
>> b/Documentation/devicetree/bindings/phy/rockchip-emmc-phy.txt index
>> e3ea557..731aeb9 100644
>> --- a/Documentation/devicetree/bindings/phy/rockchip-emmc-phy.txt
>> +++ b/Documentation/devicetree/bindings/phy/rockchip-emmc-phy.txt
>> @@ -14,6 +14,11 @@ specified by name:
>>  		access to it), it is strongly suggested.
>>   - clocks: Should have a phandle to the card clock exported by the SDHCI
>> driver.
>>
>> +Optional Properties:
>> +- drive_impedance: Must be one of 33, 40, 50, 66, 100. This property allows
>> +	different boards to specify their own drive impedance depending on the
>> +	hardware condition.
>
> In what unit are your 33, 40 etc values?
>
> It is recommended that properties should specify their unit, see all the
> properties ending in "-ma", "-ns" and so on and also
> Documentation/devicetree/bindings/property-units.txt
>
> Also properties should use dashes ("-") not underscores.
>
> Judging by the second patch, these are Ohm, so combining the above you
> probably want
>
> 	drive-impedance-ohms
>
> as property name.
>
> Also the patch subject is slightly misleading and should probably specify the
> rockchip-emmc as well :-)

Thanks, will fix them.

>
>
> Heiko
>
>
>


-- 
Best Regards
Shawn Lin