Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1496029

Re: [RFC 1/2] sdhci: Add device tree property sd-broken-highspeed

Show all headers | View raw

On Wed, Oct 5, 2016 at 1:33 PM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> On 23 September 2016 at 22:01, Zach Brown <zach.brown@ni.com> 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 <zach.brown@ni.com>
>> ---
>>  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

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[RFC 0/2] Add device tree property and quirk for supporting sdhci Zach Brown <zach.brown@ni.com> - 2016-09-23 22:30 +0200
  [RFC 1/2] sdhci: Add device tree property sd-broken-highspeed Zach Brown <zach.brown@ni.com> - 2016-09-23 22:30 +0200
    Re: [RFC 1/2] sdhci: Add device tree property sd-broken-highspeed Rob Herring <robh@kernel.org> - 2016-10-03 19:40 +0200
    Re: [RFC 1/2] sdhci: Add device tree property sd-broken-highspeed Ulf Hansson <ulf.hansson@linaro.org> - 2016-10-05 20:50 +0200
      Re: [RFC 1/2] sdhci: Add device tree property sd-broken-highspeed Rob Herring <robh+dt@kernel.org> - 2016-10-05 22:10 +0200
        Re: [RFC 1/2] sdhci: Add device tree property sd-broken-highspeed Julia Cartwright <julia@ni.com> - 2016-10-05 23:30 +0200
          Re: [RFC 1/2] sdhci: Add device tree property sd-broken-highspeed Shawn Lin <shawn.lin@rock-chips.com> - 2016-10-06 03:40 +0200
            Re: [RFC 1/2] sdhci: Add device tree property sd-broken-highspeed Adrian Hunter <adrian.hunter@intel.com> - 2016-10-06 08:20 +0200
        Re: [RFC 1/2] sdhci: Add device tree property sd-broken-highspeed Ulf Hansson <ulf.hansson@linaro.org> - 2016-10-06 10:10 +0200

csiph-web