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After commit7999eecb7e("i2c: exynos5: fix arbitration lost handling"), some I2C transactions are failing because the TRANSFER_DONE_AUTO field is not set in the I2C_TRANS_STATUS register so the i2c->status value is left to -EINVAL causing the i2c->msg_complete completion to never be signaled. For example, when reading the time of an I2C rtc on an Exynos5800 machine: $ cat /sys/class/rtc/rtc0/time [ 25.924594] exynos5-hsi2c 12e10000.i2c: rx timeout [ 65.028365] max77686-rtc max77802-rtc: Fail to read time reg(-22) cat: /sys/class/rtc/rtc0/time: Invalid argument The Exynos5422 manual states clearly that most I2C_TRANS_STATUS reg bits (including TRANSFER_DONE_AUTO) are cleared after the register is read. So reading has side effects and should only be done if HSI2C_INT_I2C was set. Fixes:7999eecb7e("i2c: exynos5: fix arbitration lost handling") Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com> Reviewed-by: Andrzej Hajda <a.hajda@samsung.com> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.