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At bind time, vc4_v3d_bind() will read a register to retrieve the v3d version and make sure it's a version we're compatible with. However, the v3d has an optional clock that is enabled only after the register read-out and a power domain that wasn't enabled at all in the bind implementation. This was working fine at boot because both were enabled, but resulted in the version check failing if we were unbinding and rebinding the driver because the unbinding would have turned them off. The fix isn't as easy as calling pm_runtime_resume_and_get() prior to the register access to power up the power domain though. Indeed, the runtime_resume implementation will enable the clock mentioned above, call vc4_v3d_init_hw() and then vc4_irq_enable(). Prior to the previous patch, vc4_irq_enable() needed to occur after our call to platform_get_irq() and vc4_irq_install(), since vc4_irq_enable() used to call enable_irq() and vc4_irq_install() will call request_irq(). vc4_irq_install() will also do some register access, so needs the power domain to be on. So we ended up in a situation where vc4_v3d_runtime_resume() needed vc4_irq_install() to have been called before, and vc4_irq_install() needed vc4_v3d_runtime_resume(). The previous patch removed the enable_irq() call in vc4_irq_enable() and thus removed the dependency of vc4_v3d_runtime_resume() on vc4_irq_install(). Thus, we can now rework our bind implementation to call pm_runtime_resume_and_get() before our register access to make sure the power domain is on. vc4_v3d_runtime_resume() also takes care of turning the clock on and calling vc4_v3d_init_hw() so we can remove them from bind. Acked-by: Thomas Zimmermann <tzimmermann@suse.de> Signed-off-by: Maxime Ripard <maxime@cerno.tech> Link: https://lore.kernel.org/r/20220711173939.1132294-69-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.