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Wed, 07 Apr 2021 05:15:13 -0700 Received: from MTKMBS31N1.mediatek.inc (172.27.4.69) by MTKMBS62N2.mediatek.inc (172.29.193.42) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 7 Apr 2021 05:15:12 -0700 Received: from MTKCAS32.mediatek.inc (172.27.4.184) by MTKMBS31N1.mediatek.inc (172.27.4.69) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 7 Apr 2021 20:15:07 +0800 Received: from [10.17.3.153] (10.17.3.153) by MTKCAS32.mediatek.inc (172.27.4.170) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Wed, 7 Apr 2021 20:15:06 +0800 Message-ID: <1617797706.32076.1.camel@mhfsdcap03> Subject: Re: [RESEND] i2c: mediatek: Get device clock-stretch time via dts From: Qii Wang To: Wolfram Sang CC: , , , , , , Date: Wed, 7 Apr 2021 20:15:06 +0800 In-Reply-To: <20210406194856.GF3122@kunai> References: <1615622664-15032-1-git-send-email-qii.wang@mediatek.com> <20210406194856.GF3122@kunai> X-Mailer: Evolution 3.10.4-0ubuntu2 MIME-Version: 1.0 X-TM-SNTS-SMTP: 4B9A90AB75786AB472DAB22F2EC572602C5BF8B0252F9FE5E8EC257F3838AAC72000:8 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210407_131523_760776_BA0D5015 X-CRM114-Status: GOOD ( 14.85 ) 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 Tue, 2021-04-06 at 21:48 +0200, Wolfram Sang wrote: > On Sat, Mar 13, 2021 at 04:04:24PM +0800, qii.wang@mediatek.com wrote: > > From: Qii Wang > > > > tSU,STA/tHD,STA/tSU,STOP maybe out of spec due to device > > clock-stretching or circuit loss, we could get device > > clock-stretch time from dts to adjust these parameters > > to meet the spec via EXT_CONF register. > > > > Signed-off-by: Qii Wang > > I tried to understand from the code what the new binding expresses, but > I don't fully understand it. Is it the maximum clock stretch time? > Because I cannot recall a device which always uses the same delay for > clock stretching. > Due to clock stretch, our HW IP cannot meet the ac-timing spec(tSU;STA,tSU;STO). There isn't a same delay for clock stretching, so we need pass a parameter which can be found through measurement to meet most conditions. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel