drm/msm: add a kernel param to select between MDP5 and DPU drivers

For some of the platforms (e.g. SDM660, SDM630, MSM8996, etc.) it is
possible to support this platform via the DPU driver (e.g. to provide
support for DP, multirect, etc). Add a modparam to be able to switch
between these two drivers.

All platforms supported by both drivers are by default handled by the
MDP5 driver. To let them be handled by the DPU driver pass the
`msm.prefer_mdp5=false` kernel param.

Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Carl Vanderlip <quic_carlv@quicinc.com>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/577504/
Link: https://lore.kernel.org/r/20240208-fd-migrate-mdp5-v4-3-945d08ef3fa8@linaro.org

drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c

@@ -1279,6 +1279,9 @@ static int dpu_dev_probe(struct platform_device *pdev)
 	int irq;
 	int ret = 0;
 
+	if (!msm_disp_drv_should_bind(&pdev->dev, true))
+		return -ENODEV;
+
 	dpu_kms = devm_kzalloc(dev, sizeof(*dpu_kms), GFP_KERNEL);
 	if (!dpu_kms)
 		return -ENOMEM;

drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c

@@ -852,6 +852,9 @@ static int mdp5_dev_probe(struct platform_device *pdev)
 
 	DBG("");
 
+	if (!msm_disp_drv_should_bind(&pdev->dev, false))
+		return -ENODEV;
+
 	mdp5_kms = devm_kzalloc(&pdev->dev, sizeof(*mdp5_kms), GFP_KERNEL);
 	if (!mdp5_kms)
 		return -ENOMEM;

drivers/gpu/drm/msm/msm_drv.c

@@ -969,6 +969,37 @@ static int add_components_mdp(struct device *master_dev,
 	return 0;
 }
 
+#if !IS_REACHABLE(CONFIG_DRM_MSM_MDP5) || !IS_REACHABLE(CONFIG_DRM_MSM_DPU)
+bool msm_disp_drv_should_bind(struct device *dev, bool dpu_driver)
+{
+	/* If just a single driver is enabled, use it no matter what */
+	return true;
+}
+#else
+
+static bool prefer_mdp5 = true;
+MODULE_PARM_DESC(prefer_mdp5, "Select whether MDP5 or DPU driver should be preferred");
+module_param(prefer_mdp5, bool, 0444);
+
+/* list all platforms supported by both mdp5 and dpu drivers */
+static const char *const msm_mdp5_dpu_migration[] = {
+	NULL,
+};
+
+bool msm_disp_drv_should_bind(struct device *dev, bool dpu_driver)
+{
+	/* If it is not an MDP5 device, do not try MDP5 driver */
+	if (!of_device_is_compatible(dev->of_node, "qcom,mdp5"))
+		return dpu_driver;
+
+	/* If it is not in the migration list, use MDP5 */
+	if (!of_device_compatible_match(dev->of_node, msm_mdp5_dpu_migration))
+		return !dpu_driver;
+
+	return prefer_mdp5 ? !dpu_driver : dpu_driver;
+}
+#endif
+
 /*
  * We don't know what's the best binding to link the gpu with the drm device.
  * Fow now, we just hunt for all the possible gpus that we support, and add them

drivers/gpu/drm/msm/msm_drv.h

@@ -563,5 +563,6 @@ int msm_drv_probe(struct device *dev,
 	struct msm_kms *kms);
 void msm_kms_shutdown(struct platform_device *pdev);
 
+bool msm_disp_drv_should_bind(struct device *dev, bool dpu_driver);
 
 #endif /* __MSM_DRV_H__ */