On Jul 22, 2013, at 4:47 AM, Wrobel Heinz-R39252 wrote:
>> Subject: [PATCH 1/2] Powerpc: Add voltage ranges support for T4
>>
>> Special voltages that can be support by eSDHC of T4 in esdhc node.
>>
>> Signed-off-by: Haijun Zhang <haijun.zhang@xxxxxxxxxxxxx>
>> Signed-off-by: Anton Vorontsov <cbouatmailru@xxxxxxxxx>
>
>> --- a/Documentation/devicetree/bindings/mmc/fsl-esdhc.txt
>> +++ b/Documentation/devicetree/bindings/mmc/fsl-esdhc.txt
>> @@ -19,6 +19,8 @@ Optional properties:
>> "bus-width = <1>" property.
>> - sdhci,auto-cmd12: specifies that a controller can only handle auto
>> CMD12.
>> + - 3300 3300: specifies that eSDHC controller can support voltages
>> ranges
>> + from 3300 to 3300. This is an optional.
>
> "This is an optional." is an unclear statement.
>
>> +++ b/arch/powerpc/boot/dts/fsl/t4240si-post.dtsi
>> @@ -399,6 +399,7 @@
>> sdhc@114000 {
>> compatible = "fsl,t4240-esdhc", "fsl,esdhc";
>> sdhci,auto-cmd12;
>> + voltage-ranges = <1800 1800 3300 3300>;
>
> This is IMHO incorrect and potentially dangerous.
> The T4 silicon will only support 1.8V on SDHC pins per hardware specification.
> The Freescale T4240QDS reference board has extra voltage shifters added to allow 3.3V operation, but that is _not_ a silicon feature. It is a specific board feature that may or may not translate to other boards, depending on how SD spec conformant a board builder wants to be.
>
> If the intent is to state that a physical SDHC interface on a board has to be built to support 3.3V operation to be SD spec conformant for off-the-shelf cards because a reset would change the signal voltage to 3.3V, then I am not sure that putting this down as silicon "feature" without further explanation about the background anywhere is the right way to go.
> IMHO silicon features are really just silicon features and not technically optional external circuitry additions implied by common use.
>
> Best regards,
>
> Heinz
I'd say that the t4240si-post.dtsi should be:
voltage-ranges = <1800 1800>;
Than have the t4240qds.dts do:
voltage-ranges = <1800 1800 3300 3300>;
As the 3.3V sounds like a board specific feature.
[ send this as 2 patches, on for the t4240si-post.dtsi and another for the t4240qds.dts ]
- k
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