Re: [PATCH] i2c: bcm2835: Model Divider in CCF

[Stefan Wahren <stefan.wahren@i2se.com>]

Hi Annaliese,

Am 05.05.19 um 05:43 schrieb Annaliese McDermond:
> 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.

i think i understand the problem, but could you please explain the
specific use case where this happend?

I suspect bcm2835 is not the only platform which is affected, so it
would be better to fix this in general.

Regards

Stefan