From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Herring Subject: Re: [RFC 1/2] sdhci: Add device tree property sd-broken-highspeed Date: Wed, 5 Oct 2016 15:03:44 -0500 Message-ID: References: <1474660869-15532-1-git-send-email-zach.brown@ni.com> <1474660869-15532-2-git-send-email-zach.brown@ni.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: Sender: linux-mmc-owner@vger.kernel.org To: Ulf Hansson Cc: Zach Brown , Adrian Hunter , Mark Rutland , linux-mmc , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" List-Id: devicetree@vger.kernel.org On Wed, Oct 5, 2016 at 1:33 PM, Ulf Hansson wrote: > On 23 September 2016 at 22:01, Zach Brown wrote: >> Certain board configurations can make highspeed malfunction due to >> timing issues. In these cases a way is needed to force the controller >> and card into standard speed even if they otherwise appear to be capable >> of highspeed. >> >> The sd-broken-highspeed property will let the sdhci driver know that >> highspeed will not work. >> >> Signed-off-by: Zach Brown >> --- >> Documentation/devicetree/bindings/mmc/mmc.txt | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/Documentation/devicetree/bindings/mmc/mmc.txt b/Documentation/devicetree/bindings/mmc/mmc.txt >> index 8a37782..59332ea 100644 >> --- a/Documentation/devicetree/bindings/mmc/mmc.txt >> +++ b/Documentation/devicetree/bindings/mmc/mmc.txt >> @@ -52,6 +52,8 @@ Optional properties: >> - no-sdio: controller is limited to send sdio cmd during initialization >> - no-sd: controller is limited to send sd cmd during initialization >> - no-mmc: controller is limited to send mmc cmd during initialization >> +- sd-broken-highspeed: Highspeed is broken, even if the controller and card >> + themselves claim they support highspeed. > > Regarding a broken card, that is managed via the card quirks and not in DT. > > If this is about a controller limitation, we already have the option > to describe what it supports, so we don't need an option to tell what > it *not* supports. > > For example "cap-sd-highspeed" tells whether the controller supports > SD high-speed, please use that instead. If a controller has a capability register and it lies (perhaps the board has limitations that the SoC does not), then you may need to disable a feature. Rob