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Mon, 25 Mar 2019 02:44:02 -0700 (PDT) Message-ID: <283b286671a65160ac8ae08b1e1889bc029db363.camel@baylibre.com> Subject: Re: [PATCH 0/2] pinctrl: meson: add g12a drive strength support From: Jerome Brunet To: Linus Walleij , Kevin Hilman , =?UTF-8?Q?Go=C5=82aszewski=2C?= Bartosz , Kevin Hilman Date: Mon, 25 Mar 2019 10:44:00 +0100 In-Reply-To: <20190314163725.7918-1-jbrunet@baylibre.com> References: <20190314163725.7918-1-jbrunet@baylibre.com> User-Agent: Evolution 3.30.5 (3.30.5-1.fc29) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190325_094406_735587_74F89CBC X-CRM114-Status: GOOD ( 28.61 ) X-BeenThere: linux-amlogic@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: devicetree@vger.kernel.org, linux-gpio@vger.kernel.org, Guillaume La Roque , linux-kernel@vger.kernel.org, linux-amlogic@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-amlogic" Errors-To: linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org On Thu, 2019-03-14 at 17:37 +0100, Jerome Brunet wrote: > The purpose of this patchset is to add drive-strength support in meson pinconf > driver. This is a new feature that was added on the g12a. It is critical for us > to support this since many functions are failing with default pad drive-strength. > > Now the slightly annoying part :( > The value achievable by the SoC are 0.5mA, 2.5mA, 3mA and 4mA and the DT property > 'drive-strength' is expressed in mA. > > 1) Rounding down the value, we could be requesting a 0mA drive strength. > That would look weird. > 2) Rounding up, we can't distinguish between 2.5mA and 3mA > > To solve this issue in this in this v1, we chose to document that, on Amlogic, > drive-strength is expressed in uA instead of mA. > It works well and there is no impact on the other platforms but I'm not sure this > is really OK with the DT rules ? > > Linus, if this is not OK with you, here are 2 other options we are > considering. We would be very interested to get your opinion on the matter: > > 1) instead the generic 'drive-strength' property, we could add an amlogic > specific property, 'amlogic,drive-strength'. It would be expressed in uA > and parsed in amlogic specific code. > I think this option is kind of overkill. Expressing drive strength in uA is > not really amlogic specific so it does not make much sense, but it would > work ... > > 2) Add another generic property "drive-strength-uA". The change to do so > would be minimal and could be benefit to other platforms later on. Hi Linus, I know it has only been 10 days and you must be busy but I was wondering if we could get your view on the issue above ? Since the vast majority of SoC functions need a drive strength setting, DT patches are somehow blocked until we decide which binding to use for it. Sorry for this early ping. Jerome > > Cheers > Jerome > > Guillaume La Roque (2): > dt-bindings: pinctrl: meson: Add drive-strength property > pinctrl: meson: add support of drive-strength > > .../bindings/pinctrl/meson,pinctrl.txt | 3 + > drivers/pinctrl/meson/pinctrl-meson-g12a.c | 36 ++-- > drivers/pinctrl/meson/pinctrl-meson.c | 166 +++++++++++++----- > drivers/pinctrl/meson/pinctrl-meson.h | 20 ++- > 4 files changed, 165 insertions(+), 60 deletions(-) > _______________________________________________ linux-amlogic mailing list linux-amlogic@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-amlogic