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Date: Tue, 12 Jul 2022 07:41:06 -0500 From: Dinh Nguyen <dinguyen@...nel.org> To: Wolfram Sang <wsa@...nel.org>, jarkko.nikula@...ux.intel.com, andriy.shevchenko@...ux.intel.com, mika.westerberg@...ux.intel.com, robh+dt@...nel.org, krzk+dt@...nel.org, linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org, devicetree@...r.kernel.org Subject: Re: [PATCHv6 1/2] i2c: designware: introduce a custom scl recovery for SoCFPGA platforms Hi Wolfram, On 6/22/22 15:07, Wolfram Sang wrote: > >> From the original code, the first mechanism to a recovery is to acquire a >> GPIO for the SCL line and send the 9 SCL pulses, after that, it does a reset >> of the I2C module. For the SOCFPGA part, there is no GPIO line for the SCL, >> thus the I2C module cannot even get a reset. This code allows the function >> to reset the I2C module for SOCFPGA, which is the 2nd part of the recovery >> process. > > The second part is totally useless if the client device is holding SDA > low. Which is exactly the situation that recovery tries to fix. As I > said, if you can't control SCL, you don't have recovery. > This is recovery of the master and not the slave. We have a customer that is the using I2C with the signals routed through the FPGA, and thus are not GPIO. During a timeout, with this code, the driver is able to recover the master. Dinh
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