From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 6826F2C00A8 for ; Tue, 23 Jul 2013 00:40:21 +1000 (EST) Subject: Re: [PATCH 1/2] Powerpc: Add voltage ranges support for T4 Mime-Version: 1.0 (Apple Message framework v1283) Content-Type: text/plain; charset=us-ascii From: Kumar Gala In-Reply-To: <192298D25D96A042975E372855100DB70A1A93DC@039-SN2MPN1-012.039d.mgd.msft.net> Date: Mon, 22 Jul 2013 09:39:41 -0500 Message-Id: <18210A71-9F5A-40B7-AC3A-03CEF6C28982@kernel.crashing.org> References: <1374479636-9254-1-git-send-email-Haijun.Zhang@freescale.com> <192298D25D96A042975E372855100DB70A1A93DC@039-SN2MPN1-012.039d.mgd.msft.net> To: Wrobel Heinz-R39252 Cc: Wood Scott-B07421 , "linux-mmc@vger.kernel.org" , Zhang Haijun-B42677 , Fleming Andy-AFLEMING , "cbouatmailru@gmail.com" , "cjb@laptop.org" , "linuxppc-dev@lists.ozlabs.org" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Jul 22, 2013, at 4:47 AM, Wrobel Heinz-R39252 wrote: >> Subject: [PATCH 1/2] Powerpc: Add voltage ranges support for T4 >>=20 >> Special voltages that can be support by eSDHC of T4 in esdhc node. >>=20 >> Signed-off-by: Haijun Zhang >> Signed-off-by: Anton Vorontsov >=20 >> --- a/Documentation/devicetree/bindings/mmc/fsl-esdhc.txt >> +++ b/Documentation/devicetree/bindings/mmc/fsl-esdhc.txt >> @@ -19,6 +19,8 @@ Optional properties: >> "bus-width =3D <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. >=20 > "This is an optional." is an unclear statement. >=20 >> +++ b/arch/powerpc/boot/dts/fsl/t4240si-post.dtsi >> @@ -399,6 +399,7 @@ >> sdhc@114000 { >> compatible =3D "fsl,t4240-esdhc", "fsl,esdhc"; >> sdhci,auto-cmd12; >> + voltage-ranges =3D <1800 1800 3300 3300>; >=20 > 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. >=20 > 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. >=20 > Best regards, >=20 > Heinz I'd say that the t4240si-post.dtsi should be: voltage-ranges =3D <1800 1800>; Than have the t4240qds.dts do: voltage-ranges =3D <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 =09=