linux-imx

LF-794-3 gpu: cdn: imx8qm: Add firmware loading support

This allows the  HDP i.MX8QM driver to load the firmware on init
and resume. In order to have backward compatibility, if there is
no firmware-name property defined in the hdmi node, the driver
probing sequence skips the firmware loading.

Also, if u-boot has loaded already a firmware, we run with that
but when probing the driver, the request_firmware_nowait is used
to locate and keep safe the firmware for when suspend/resume happens.

This leads to 4 possible scenarios:

1. u-boot loads the firmware, the kernel driver finds the firmware
when rootfs is mounted. This is the most desirable scenario. Also
this is the only scenario that allows the hdmi to work after resume.

2. u-boot loads the firmware, the kernel driver _doesn't_ find
the firmware in rootfs. If there is no suspend ever happening,
the kernel driver will keep using the firmware that was loaded by
u-boot. On the first suspend/resume, the firmware is lost
because the HDMI IP gets powered down.

3. u-boot doesn't load the firmare, the kernel driver probing
tries to load the firmware, assuming this is available
(see CONFIG_EXTRA_FIRMWARE).

4. u-boot doesn't load the firmware and the kernel driver is not
able to find it either. The probing fails and there is no HDMI
available in linux.

Signed-off-by: Abel Vesa <abel.vesa@nxp.com>
Reviewed-by: Sandor Yu <sandor.yu@nxp.com>
Acked-by: Wen He <wen.he_1@nxp.com>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>