remoteproc: imx_rproc: skip clock enable when M-core is managed by the SCU

remoteproc: imx_rproc: skip clock enable when M-core is managed by the SCU

[ Upstream commit 496deecb020d14ba89ba7084fbc3024f91687023 ]

For the i.MX8X and i.MX8 family SoCs, when the Cortex-M core is powered
up and started by the Cortex-A core using the bootloader (e.g., via the
U-Boot bootaux command), both M-core and Linux run within the same SCFW
(System Controller Firmware) partition. With that, Linux has permission
to control the M-core.

But once the M-core is started by the bootloader, the SCFW automatically
enables its clock and sets the clock rate. If Linux later attempts to
enable the same clock via clk_prepare_enable(), the SCFW returns a
'LOCKED' error, as the clock is already configured by the SCFW. This
causes the probe function in imx_rproc.c to fail, leading to the M-core
power domain being shut down while the core is still running. This
results in a fault from the SCU (System Controller Unit) and triggers a
system reset.

To address this issue, ignore handling the clk for i.MX8X and i.MX8
M-core, as SCFW already takes care of enabling and configuring the
clock.

Suggested-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Hiago De Franco <hiago.franco@toradex.com>
Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20250629172512.14857-3-hiagofranco@gmail.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>