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Wed, 14 Jul 2021 00:49:47 -0700 Received: from MTKMBS31N1.mediatek.inc (172.27.4.69) by MTKMBS62N1.mediatek.inc (172.29.193.41) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 14 Jul 2021 00:49:46 -0700 Received: from MTKCAS36.mediatek.inc (172.27.4.186) by MTKMBS31N1.mediatek.inc (172.27.4.69) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 14 Jul 2021 15:49:39 +0800 Received: from [10.17.3.153] (10.17.3.153) by MTKCAS36.mediatek.inc (172.27.4.170) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Wed, 14 Jul 2021 15:49:39 +0800 Message-ID: <1626248978.8985.4.camel@mhfsdcap03> Subject: Re: [PATCH V3 2/3] dt-bindings: i2c: add attribute default-timing-adjust From: Kewei Xu To: Rob Herring CC: , , , , , , , , , , , , , Date: Wed, 14 Jul 2021 15:49:38 +0800 In-Reply-To: <20210712205342.GA2469648@robh.at.kernel.org> References: <1624271985-23591-1-git-send-email-kewei.xu@mediatek.com> <1624271985-23591-3-git-send-email-kewei.xu@mediatek.com> <20210712205342.GA2469648@robh.at.kernel.org> X-Mailer: Evolution 3.10.4-0ubuntu2 MIME-Version: 1.0 X-TM-SNTS-SMTP: F8EAEF2BEC1C758AA1F1F56F12303E5B8C124DDF5593E1195846295ACC508F7A2000:8 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210714_004954_346252_890DD204 X-CRM114-Status: GOOD ( 20.53 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 2021-07-12 at 14:53 -0600, Rob Herring wrote: > On Mon, Jun 21, 2021 at 06:39:44PM +0800, kewei.xu@mediatek.com wrote: > > From: Kewei Xu > > > > Add attribute default-timing-adjust for DT-binding document. > > > > Fixes: be5ce0e97cc7 ("i2c: mediatek: Add i2c ac-timing adjust support") > > You want to fix a kernel change with a DT change? That's not a > compatible change (and I guess neither was the kernel change). Sounds > like the above commit should be reverted and rethink how to add a new > feature... > > > Signed-off-by: Kewei Xu > > --- > > Documentation/devicetree/bindings/i2c/i2c-mt65xx.txt | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/Documentation/devicetree/bindings/i2c/i2c-mt65xx.txt b/Documentation/devicetree/bindings/i2c/i2c-mt65xx.txt > > index 7c4915bc..7b80a11 100644 > > --- a/Documentation/devicetree/bindings/i2c/i2c-mt65xx.txt > > +++ b/Documentation/devicetree/bindings/i2c/i2c-mt65xx.txt > > @@ -33,6 +33,8 @@ Optional properties: > > - mediatek,have-pmic: platform can control i2c form special pmic side. > > Only mt6589 and mt8135 support this feature. > > - mediatek,use-push-pull: IO config use push-pull mode. > > + - mediatek,default-timing-adjust: use default timing calculation, no timing > > + adjustment. > > > > Example: > > > > -- > > 1.9.1 > > > > Hi Rob, In the commit be5ce0e97cc7 ("i2c: mediatek: Add i2c ac-timing adjust support"), the I2C timing calculation has been revised to support ac-timing adjustment.But in our design, it will make tSU,STA/tHD,STA/tSU,STO shorter when the slave device have clock-stretching feature. Then we upload the commit a80f24945fcf ("i2c: mediatek: Use scl_int_delay_ns to compensate clock-stretching") to support adjusting tSU,STA/tHD,STA/tSU,STO when the slave device clock-stretching. But if the slave device stretch the SCL line for too long time, our design still cannot make tSU,STA/tHD,STA/tSU,STO meet spec. However in the old (default) timing algorithm before the commit be5ce0e97cc7 ("i2c: mediatek: Add i2c ac-timing adjust support"), tSU,STA/tHD,STA/tSU,STO can meet spec. So we want to define a new setting "default-adjust-timing" for using the old (default) timing algorithm. thanks kewei _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel