Thanks. Regards Haijun. > -----Original Message----- > From: Kumar Gala [mailto:galak@xxxxxxxxxxxxxxxxxxx] > Sent: Monday, July 22, 2013 10:40 PM > To: Wrobel Heinz-R39252 > Cc: Zhang Haijun-B42677; linux-mmc@xxxxxxxxxxxxxxx; linuxppc- > dev@xxxxxxxxxxxxxxxx; Wood Scott-B07421; cjb@xxxxxxxxxx; Fleming Andy- > AFLEMING; cbouatmailru@xxxxxxxxx > Subject: Re: [PATCH 1/2] Powerpc: Add voltage ranges support for T4 > > > 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 ] [Haijun Wrote:] ok, thanks Heinz and Kumar. > > - k > -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
