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.comSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/flexcan/flexcan-core.c

@@ -354,6 +354,14 @@ static struct flexcan_devtype_data fsl_imx93_devtype_data = {
 		FLEXCAN_QUIRK_SUPPORT_RX_MAILBOX_RTR,
 };
 
+static const struct flexcan_devtype_data fsl_imx95_devtype_data = {
+	.quirks = FLEXCAN_QUIRK_DISABLE_RXFG | FLEXCAN_QUIRK_ENABLE_EACEN_RRS |
+		FLEXCAN_QUIRK_DISABLE_MECR | FLEXCAN_QUIRK_USE_RX_MAILBOX |
+		FLEXCAN_QUIRK_BROKEN_PERR_STATE | FLEXCAN_QUIRK_SUPPORT_FD |
+		FLEXCAN_QUIRK_SUPPORT_ECC | FLEXCAN_QUIRK_SUPPORT_RX_MAILBOX |
+		FLEXCAN_QUIRK_SUPPORT_RX_MAILBOX_RTR | FLEXCAN_QUIRK_SETUP_STOP_MODE_SCMI,
+};
+
 static const struct flexcan_devtype_data fsl_vf610_devtype_data = {
 	.quirks = FLEXCAN_QUIRK_DISABLE_RXFG | FLEXCAN_QUIRK_ENABLE_EACEN_RRS |
 		FLEXCAN_QUIRK_DISABLE_MECR | FLEXCAN_QUIRK_USE_RX_MAILBOX |
@@ -544,6 +552,13 @@ static inline int flexcan_enter_stop_mode(struct flexcan_priv *priv)
 	} else if (priv->devtype_data.quirks & FLEXCAN_QUIRK_SETUP_STOP_MODE_GPR) {
 		regmap_update_bits(priv->stm.gpr, priv->stm.req_gpr,
 				   1 << priv->stm.req_bit, 1 << priv->stm.req_bit);
+	} else if (priv->devtype_data.quirks & FLEXCAN_QUIRK_SETUP_STOP_MODE_SCMI) {
+		/* For the SCMI mode, driver do nothing, ATF will send request to
+		 * SM(system manager, M33 core) through SCMI protocol after linux
+		 * suspend. Once SM get this request, it will send IPG_STOP signal
+		 * to Flex_CAN, let CAN in STOP mode.
+		 */
+		return 0;
 	}
 
 	return flexcan_low_power_enter_ack(priv);
@@ -555,7 +570,11 @@ static inline int flexcan_exit_stop_mode(struct flexcan_priv *priv)
 	u32 reg_mcr;
 	int ret;
 
-	/* remove stop request */
+	/* Remove stop request, for FLEXCAN_QUIRK_SETUP_STOP_MODE_SCMI,
+	 * do nothing here, because ATF already send request to SM before
+	 * linux resume. Once SM get this request, it will deassert the
+	 * IPG_STOP signal to Flex_CAN.
+	 */
 	if (priv->devtype_data.quirks & FLEXCAN_QUIRK_SETUP_STOP_MODE_SCFW) {
 		ret = flexcan_stop_mode_enable_scfw(priv, false);
 		if (ret < 0)
@@ -1983,6 +2002,9 @@ static int flexcan_setup_stop_mode(struct platform_device *pdev)
 		ret = flexcan_setup_stop_mode_scfw(pdev);
 	else if (priv->devtype_data.quirks & FLEXCAN_QUIRK_SETUP_STOP_MODE_GPR)
 		ret = flexcan_setup_stop_mode_gpr(pdev);
+	else if (priv->devtype_data.quirks & FLEXCAN_QUIRK_SETUP_STOP_MODE_SCMI)
+		/* ATF will handle all STOP_IPG related work */
+		ret = 0;
 	else
 		/* return 0 directly if doesn't support stop mode feature */
 		return 0;
@@ -2009,6 +2031,7 @@ static const struct of_device_id flexcan_of_match[] = {
 	{ .compatible = "fsl,imx8qm-flexcan", .data = &fsl_imx8qm_devtype_data, },
 	{ .compatible = "fsl,imx8mp-flexcan", .data = &fsl_imx8mp_devtype_data, },
 	{ .compatible = "fsl,imx93-flexcan", .data = &fsl_imx93_devtype_data, },
+	{ .compatible = "fsl,imx95-flexcan", .data = &fsl_imx95_devtype_data, },
 	{ .compatible = "fsl,imx6q-flexcan", .data = &fsl_imx6q_devtype_data, },
 	{ .compatible = "fsl,imx28-flexcan", .data = &fsl_imx28_devtype_data, },
 	{ .compatible = "fsl,imx53-flexcan", .data = &fsl_imx25_devtype_data, },
@@ -2309,9 +2332,19 @@ static int __maybe_unused flexcan_noirq_suspend(struct device *device)
 		if (device_may_wakeup(device))
 			flexcan_enable_wakeup_irq(priv, true);
 
-		err = pm_runtime_force_suspend(device);
-		if (err)
-			return err;
+		/* For FLEXCAN_QUIRK_SETUP_STOP_MODE_SCMI, it need ATF to send
+		 * to SM through SCMI protocol, SM will assert the IPG_STOP
+		 * signal. But all this works need the CAN clocks keep on.
+		 * After the CAN module get the IPG_STOP mode, and switch to
+		 * STOP mode, whether still keep the CAN clocks on or gate them
+		 * off depend on the Hardware design.
+		 */
+		if (!(device_may_wakeup(device) &&
+		      priv->devtype_data.quirks & FLEXCAN_QUIRK_SETUP_STOP_MODE_SCMI)) {
+			err = pm_runtime_force_suspend(device);
+			if (err)
+				return err;
+		}
 	}
 
 	return 0;
@@ -2325,9 +2358,12 @@ static int __maybe_unused flexcan_noirq_resume(struct device *device)
 	if (netif_running(dev)) {
 		int err;
 
-		err = pm_runtime_force_resume(device);
-		if (err)
-			return err;
+		if (!(device_may_wakeup(device) &&
+		      priv->devtype_data.quirks & FLEXCAN_QUIRK_SETUP_STOP_MODE_SCMI)) {
+			err = pm_runtime_force_resume(device);
+			if (err)
+				return err;
+		}
 
 		if (device_may_wakeup(device))
 			flexcan_enable_wakeup_irq(priv, false);

drivers/net/can/flexcan/flexcan.h

@@ -68,6 +68,8 @@
 #define FLEXCAN_QUIRK_SUPPORT_RX_MAILBOX_RTR BIT(15)
 /* Device supports RX via FIFO */
 #define FLEXCAN_QUIRK_SUPPORT_RX_FIFO BIT(16)
+/* Setup stop mode with ATF SCMI protocol to support wakeup */
+#define FLEXCAN_QUIRK_SETUP_STOP_MODE_SCMI BIT(17)
 
 struct flexcan_devtype_data {
 	u32 quirks;		/* quirks needed for different IP cores */