Hi Christoph, Am Dienstag, 12. März 2019, 15:46:44 CET schrieb Christoph Müllner: > > On 12.03.2019, at 14:17, Heiko Stuebner <heiko@xxxxxxxxx> wrote: > > > > Am Freitag, 8. März 2019, 14:10:45 CET schrieb Christoph Müllner: > >>> On 08.03.2019, at 13:46, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: > >>> > >>> On 7/03/19 10:43 AM, Christoph Muellner wrote: > >>>> This patch documents the new property disable-cqe-dcmd > >>>> for the Arasan eMMC 5.1 driver. > >>>> > >>>> Signed-off-by: Christoph Muellner > >>>> <christoph.muellner@xxxxxxxxxxxxxxxxxxxxx> Signed-off-by: Philipp > >>>> Tomsich <philipp.tomsich@xxxxxxxxxxxxxxxxxxxxx> --- > >>>> Documentation/devicetree/bindings/mmc/arasan,sdhci.txt | 4 ++++ > >>>> 1 file changed, 4 insertions(+) > >>>> > >>>> diff --git a/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt > >>>> b/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt index > >>>> 1edbb049cccb..ec699bf98b7c 100644 > >>>> --- a/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt > >>>> +++ b/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt > >>>> > >>>> @@ -44,6 +44,10 @@ Optional Properties: > >>>> properly. Test mode can be used to force the controller to function. > >>>> > >>>> - xlnx,int-clock-stable-broken: when present, the controller always > >>>> reports > >>>> > >>>> that the internal clock is stable even when it is not. > >>>> > >>>> + - disable-cqe-dcmd: The eMMC 5.1 standard specifies direct commands > >>>> (DCMDs) + as part of the command queue engine (CQE). On controllers > >>>> with a CQHCI, + such as the Arasan eMMC 5.1 host controller, the > >>>> driver has to enable DCMDs. + This is done unless disable-cqe-dcmd > >>>> is specified. > > > > This needs a rewording please. See below for hw-description vs. driver, so > > the description should be centered around why this is a property of the hw > > [like faulty controller implementation or whatever] > > I understand, that you prefer a HW-specific name for a property > over one, that explains the actual effect. Actually I think the property-name is just fine :-) . The description might profit from a rewording though. Aka not driver- centric but hw-centric, describing why some controllers may need the option to disable these dcmds (controller bugs or whatever). Heiko > However, using disable-<feature> (which is always a directive for the driver > and not a HW description) is not uncommon: > > * disable-wp should be "no-wp-line-connection" > * disable-over-current -> "no-over-current-line-connection" > * srp-disable -> "not-existing-srp-implementation" > * ... > > But I don't mind using something else. > Would "broken-cqe-dcmd" (like broken-cd or broken-flash-reset) be ok? > Or other suggestions? > > Also I'd like to mention, that my first implementation was > "supports-cqe-dcmd". I guess that would be a good choice, if it would have > been there > from the beginning. Introducing it now, would silently disable DCMD > for existing DTBs. Therefore I went on to "disable-cqe-dcmd". > > >>> If "supports-cqe" is in mmc.txt, should "disable-cqe-dcmd" be there > >>> also? > >> > >> The file mmc.txt says on top: > >> "These properties are common to multiple MMC host controllers". > >> As my patchset introduces "disable-cqe-dcmd" just for sdhci-of-arasan, > >> I would say it should not go into that file. > >> > >> Also I wonder why "supports-cqe" is in mmc.txt, because > >> only sdhci-tegra.c is evaluating that property. > >> So I would expect it to be documented in > >> Documentation/devicetree/bindings/mmc/nvidia,tegra20-sdhci.txt > >> > >> However, I see that "disable-cqe-dcmd" could go into other drivers as > >> well. > >> But is this enough to document it in mmc.txt? > > > > Devicetree is always about describing the hardware capabilites and never > > about the actual nitty-gritty of driver implementation, aka it is not > > meant > > as a space for hardware-independent config-settings or such. > > > > As for only tegra evaluating this, is probably because it is still so new, > > like january 2019 and Rob explicitly suggested it becoming common [0], > > which suggests that the disable-cqe-dcmds should probably also be common. > So mmc.txt lists "standardised" names for properties to reduce the risk > of having similar, but distinct names for different MMC drivers. > So whenever you want to introduce a new property for a driver, > check if there isn't already something defined in mmc.txt. > > When seeing it this way, it clearly makes sense to have the property there. > > Thanks, > Christoph
