Stefan -- > On Jun 19, 2019, at 12:16 AM, Stefan Wahren <stefan.wahren@xxxxxxxx> wrote: > > 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? I’ll see if I can look into these and see what’s up. > Thanks > > [1] - https://www.raspberrypi.org/forums/viewtopic.php?f=44&t=242856 > [2] - https://archlinuxarm.org/forum/viewtopic.php?f=23&t=13719 -- Annaliese McDermond nh6z@xxxxxxxx
