Hi Annaliese, On 08.06.19 19:14, Annaliese McDermond wrote: > Model the I2C bus clock divider as a part of the Core Clock Framework. > Primarily this removes the clk_get_rate() call from each transfer. > This call causes problems for slave drivers that themselves have > internal clock components that are controlled by an I2C interface. > When the slave's internal clock component is prepared, the prepare > lock is obtained, and it makes calls to the I2C subsystem to > command the hardware to activate the clock. In order to perform > the I2C transfer, this driver sets the divider, which requires > it to get the parent clock rate, which it does with clk_get_rate(). > Unfortunately, this function will try to take the clock prepare > lock, which is already held by the slave's internal clock calls > creating a deadlock. > > Modeling the divider in the CCF natively removes this dependency > and the divider value is only set upon changing the bus clock > frequency or changes in the parent clock that cascade down to this > divisor. This obviates the need to set the divider with every > transfer and avoids the deadlock described above. It also should > provide better clock debugging and save a few cycles on each > transfer due to not having to recalcuate the divider value. > i've seen reports [1], [2] that this commit causes trouble. Could you please look into them? Thanks [1] - https://www.raspberrypi.org/forums/viewtopic.php?f=44&t=242856 [2] - https://archlinuxarm.org/forum/viewtopic.php?f=23&t=13719
