drm: bridge: dw_hdmi: Add cec suspend/resume functions

CEC interrupt status/mask and logical address registers
will be reset when device enter suspend.
It will cause cec fail to work after device resume.
Add CEC suspend/resume functions, reinitialize logical address registers
and restore interrupt status/mask registers after resume.

Signed-off-by: Sandor Yu <[e-mail]>
Reviewed-by: Neil Armstrong <[e-mail]>
Signed-off-by: Neil Armstrong <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/bridge/synopsys/dw-hdmi-cec.c

···
 	bool rx_done;
 	struct cec_notifier *notify;
 	int irq;
+
+	u8 regs_polarity;
+	u8 regs_mask;
+	u8 regs_mute_stat0;
 };
 
 static void dw_hdmi_write(struct dw_hdmi_cec *cec, u8 val, int offset)
···
 	cec_unregister_adapter(cec->adap);
 }
 
+static int __maybe_unused dw_hdmi_cec_resume(struct device *dev)
+{
+	struct dw_hdmi_cec *cec = dev_get_drvdata(dev);
+
+	/* Restore logical address */
+	dw_hdmi_write(cec, cec->addresses & 255, HDMI_CEC_ADDR_L);
+	dw_hdmi_write(cec, cec->addresses >> 8, HDMI_CEC_ADDR_H);
+
+	/* Restore interrupt status/mask registers */
+	dw_hdmi_write(cec, cec->regs_polarity, HDMI_CEC_POLARITY);
+	dw_hdmi_write(cec, cec->regs_mask, HDMI_CEC_MASK);
+	dw_hdmi_write(cec, cec->regs_mute_stat0, HDMI_IH_MUTE_CEC_STAT0);
+
+	return 0;
+}
+
+static int __maybe_unused dw_hdmi_cec_suspend(struct device *dev)
+{
+	struct dw_hdmi_cec *cec = dev_get_drvdata(dev);
+
+	/* store interrupt status/mask registers */
+	 cec->regs_polarity = dw_hdmi_read(cec, HDMI_CEC_POLARITY);
+	 cec->regs_mask = dw_hdmi_read(cec, HDMI_CEC_MASK);
+	 cec->regs_mute_stat0 = dw_hdmi_read(cec, HDMI_IH_MUTE_CEC_STAT0);
+
+	return 0;
+}
+
+static const struct dev_pm_ops dw_hdmi_cec_pm = {
+	SET_SYSTEM_SLEEP_PM_OPS(dw_hdmi_cec_suspend, dw_hdmi_cec_resume)
+};
+
 static struct platform_driver dw_hdmi_cec_driver = {
 	.probe	= dw_hdmi_cec_probe,
 	.remove_new = dw_hdmi_cec_remove,
 	.driver = {
 		.name = "dw-hdmi-cec",
+		.pm = &dw_hdmi_cec_pm,
 	},
 };
 module_platform_driver(dw_hdmi_cec_driver);