From mboxrd@z Thu Jan 1 00:00:00 1970 From: dgilbert@interlog.com (Douglas Gilbert) Date: Thu, 01 Jan 2015 13:02:13 -0500 Subject: [PATCH] at91: i2c-at91: improve time-out handling Message-ID: <54A58BA5.3080003@interlog.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org With lk 3.19.0-rc2 and a at91sam9g25 (9x5) based system I connected a NXP SC16IS750 I2C to serial bridge. After routing the 750's IRQ back to the sc16is7xx driver and some simple successful test, it was time for some intense testing: Tx looped back to Rx on the 750, open picocom on /dev/ttySC0 at 38400, and use hexdump to blast a binary file (in hex) at ttySC0. The I2C SCL speed was 200,000 Hz. It worked as expected for a few seconds then it wedged the I2C bus. That was repeatable. In the cases that I checked SCL was high, SDA was low (driven by _both_ the G25's macrocell and the 750!!) and IRQ was active (low). This patch stopped the G25 macrocell from driving SDA low in the above wedge (and stopped copious error reports going to the log). I was surprised that a NXP I2C chip got into this situation, IMO SDA on a slave should have a driven low timeout. IMO all I2C master drivers should have provision to drive a gpio connected to a (or all the) slave's RESET line(s). ChangeLog: when handling an I2C bus time-out, first clean-up the DMA transfer, then do an I2C macrocell software reset and restore some registers, including the interrupt mask Signed-off-by: Douglas Gilbert -------------- next part -------------- A non-text attachment was scrubbed... Name: i2c-at91-timeout1.patch Type: text/x-patch Size: 972 bytes Desc: not available URL: