can: flexcan: add wakeup support for imx95

can: flexcan: add wakeup support for imx95

iMX95 defines a bit in GPR that sets/unsets the IPG_STOP signal to the
FlexCAN module, controlling its entry into STOP mode. Wakeup should work
even if FlexCAN is in STOP mode.

Due to iMX95 architecture design, the A-Core cannot access GPR; only the
system manager (SM) can configure GPR. To support the wakeup feature,
follow these steps:

- For suspend:
  1) During Linux suspend, when CAN suspends, do nothing for GPR and keep
     CAN-related clocks on.
  2) In ATF, check whether CAN needs to support wakeup; if yes, send a
     request to SM through the SCMI protocol.
  3) In SM, configure the GPR and unset IPG_STOP.
  4) A-Core suspends.

- For wakeup and resume:
  1) A-Core wakeup event arrives.
  2) In SM, deassert IPG_STOP.
  3) Linux resumes.

Add a new fsl_imx95_devtype_data and FLEXCAN_QUIRK_SETUP_STOP_MODE_SCMI to
reflect this.

Reviewed-by: Han Xu <han.xu@nxp.com>
Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/all/20240731-flexcan-v4-2-82ece66e5a76@nxp.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>