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On the RaspberryPi0-3, the HSM clock was provided by the clk-bcm2835 driver, but on the Pi4 it was provided by the firmware through the clk-raspberrypi driver. The clk-bcm2835 driver registers the HSM clock using the CLK_SET_RATE_GATE flag that prevents any modification to the rate while the clock is active. This meant that we needed to call clk_set_min_rate() before our call to pm_runtime_resume_and_get() since our runtime_resume implementation needs to enable the HSM clock for the HDMI controller registers to be functional. However, the HSM clock is part of the HDMI power domain which might not be powered prior to the pm_runtime_resume_and_get() call, so we could end up changing the rate of the HSM clock while its power domain was disabled. We recently changed the backing driver for the RaspberryPi0-3 to clk-raspberrypi though, which doesn't have such restrictions. We can thus move the clk_set_min_rate() after our call to runtime_resume and avoid the access while the power domain is disabled. Reviewed-by: Javier Martinez Canillas <javierm@redhat.com> Link: https://lore.kernel.org/r/20230126-rpi-display-fw-clk-cleanup-v1-2-d646ff6fb842@cerno.tech Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.