Re: [PATCH v3 3/4] drm/msm: add a kernel param to select between MDP5 and DPU drivers

[Carl Vanderlip <quic_carlv@quicinc.com>]

On 1/5/2024 3:34 PM, Dmitry Baryshkov wrote:
> 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>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c  |  3 +++
>   drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c |  3 +++
>   drivers/gpu/drm/msm/msm_drv.c            | 31 +++++++++++++++++++++++++++++++
>   drivers/gpu/drm/msm/msm_drv.h            |  1 +
>   4 files changed, 38 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> index aa9e0ad33ebb..8f11a98491a1 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> @@ -1276,6 +1276,9 @@ 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;
> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
> index 0827634664ae..43d05851c54d 100644
> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
> @@ -866,6 +866,9 @@ 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;
> diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> index 50b65ffc24b1..ef57586fbeca 100644
> --- a/drivers/gpu/drm/msm/msm_drv.c
> +++ b/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 mdp5_driver)

s/mdp5_driver/dpu_driver/

> +{
> +	/* If just a single driver is enabled, use it no matter what */
> +	return true;
> +}

This will cause both MDP/DPU probes to return -ENODEV, rather than
select the enabled one.

> +#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
> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> index 01e783130054..762e13e2df74 100644
> --- a/drivers/gpu/drm/msm/msm_drv.h
> +++ b/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__ */
>