From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Nikula Subject: Re: Regression: bd698d24b1b57: i2c: designware: Get selected speed mode sda-hold-time via ACPI Date: Fri, 19 May 2017 10:11:29 +0300 Message-ID: <2b97458f-245c-b914-bdff-8805b5b7ccbb@linux.intel.com> References: <20170509140720.GA21122@red-moon> <1494341651.30052.82.camel@linux.intel.com> <20170509155253.GA21475@red-moon> <1494346848.30052.84.camel@linux.intel.com> <20170510092450.GA26012@red-moon> <1105edd1-8649-66f2-8df8-79aeae61af3a@linux.intel.com> <25ff2580-d461-87f2-f61d-2ede10ea4c01@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-acpi-owner@vger.kernel.org To: Ard Biesheuvel Cc: Lorenzo Pieralisi , Andy Shevchenko , chin.yew.tan@intel.com, mika.westerberg@linux.intel.com, wsa@the-dreams.de, "linux-acpi@vger.kernel.org" , linux-i2c@vger.kernel.org, ken.xue@amd.com, jeff.wu@amd.com List-Id: linux-i2c@vger.kernel.org On 05/18/2017 04:44 PM, Ard Biesheuvel wrote: > On 18 May 2017 at 14:05, Jarkko Nikula wrote: >> I have a fix for this. Could you try does it fix the issue for you? >> >> http://www.spinics.net/lists/linux-i2c/msg29509.html >> > > Thanks. But the question is really whether we want to change the > driver so that the DW_IC_SS_SCL_HCNT/DW_IC_SS_SCL_LCNT registers are > no longer programmed at all when running at a higher speed. Can you > guarantee that this will not cause any change in behavior in all > instances of this hardware that are supported currently, no matter how > they are synthesized and described to the OS? The previous commit only > affected the platdrv variety AFAIR > Obviously I cannot guarantee are there any side effects as I don't know the IP. However I forgot one important point: high-speed transfers always starts in fast-mode so those timing parameters too are needed when bus is configured for high-speed. So best is to write all of them. -- Jarkko