From mboxrd@z Thu Jan 1 00:00:00 1970 From: Heiko =?ISO-8859-1?Q?St=FCbner?= Subject: Re: [PATCH v2 2/3] dt-bindings: mmc: Add a new property disable-cqe-dcmd. Date: Tue, 12 Mar 2019 18:10:56 +0100 Message-ID: <2038789.ZmMFo7ZELZ@diego> References: <20190307084329.25416-1-christoph.muellner@theobroma-systems.com> <4793843.T1TZ7EF8k3@phil> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Christoph =?ISO-8859-1?Q?M=FCllner?= Cc: mark.rutland@arm.com, ulf.hansson@linaro.org, Emil Renner Berthing , Viresh Kumar , shawn.lin@rock-chips.com, Adrian Hunter , Tony Xie , Klaus Goger , Philipp Tomsich , Michal Simek , linux-rockchip@lists.infradead.org, devicetree@vger.kernel.org, Randy Li , Vicente Bergas , robh+dt@kernel.org, Ezequiel Garcia , linux-arm-kernel@lists.infradead.org, Lin Huang , linux-mmc@vger.kernel.org, Douglas Anderson , linux-kernel@vger.kernel.org, Enric Balletbo i Serra List-Id: devicetree@vger.kernel.org Hi Christoph, Am Dienstag, 12. M=E4rz 2019, 15:46:44 CET schrieb Christoph M=FCllner: > > On 12.03.2019, at 14:17, Heiko Stuebner wrote: > > = > > Am Freitag, 8. M=E4rz 2019, 14:10:45 CET schrieb Christoph M=FCllner: > >>> On 08.03.2019, at 13:46, Adrian Hunter wrot= e: > >>> = > >>> 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 > >>>> Signed-off-by: Philipp > >>>> Tomsich --- > >>>> 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 functi= on. > >>>> = > >>>> - 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 comman= ds > >>>> (DCMDs) + as part of the command queue engine (CQE). On controlle= rs > >>>> 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- (which is always a directive for the dri= ver > 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 n= ew, > > like january 2019 and Rob explicitly suggested it becoming common [0], > > which suggests that the disable-cqe-dcmds should probably also be commo= n. > 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 ther= e. > = > Thanks, > Christoph