Re: [PATCH v7 7/7] media: mtk-mdp: use mdp-rdma0 alias to point to MDP master

[houlong wei]

Hi Eizan,

Thanks for you patch. I have inline comment below.

Regards,
Houlong

On Wed, 2021-08-25 at 14:33 +0800, Eizan Miyamoto wrote:
> ... Instead of depending on the presence of a mediatek,vpu property in
> the device node.
> 
> That property was originally added to link to the vpu node so that the
> mtk_mdp_core driver could pass the right device to
> vpu_wdt_reg_handler(). However in a previous patch in this series,
> the driver has been modified to search the device tree for that node
> instead.
> 
> That property was also used to indicate the primary MDP device, so that
> it can be passed to the V4L2 subsystem as well as register it to be
> used when setting up queues in the open() callback for the filesystem
> device node that is created. In this case, assuming that the primary
> MDP device is the one with a specific alias seems useable because the
> alternative is to add a property to the device tree which doesn't
> actually represent any facet of hardware (i.e., this being the primary
> MDP device is a software decision). In other words, this solution is
> equally as arbitrary, but at least it doesn't add a property to a
> device node where said property is unrelated to the hardware present.
> 
> Signed-off-by: Eizan Miyamoto <eizan@xxxxxxxxxxxx>
> Reviewed-by: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
> ---
> 
> (no changes since v1)
> 
>  drivers/media/platform/mtk-mdp/mtk_mdp_comp.c | 56 +++++++++++++------
>  drivers/media/platform/mtk-mdp/mtk_mdp_core.c | 36 ++++++++----
>  2 files changed, 64 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/media/platform/mtk-mdp/mtk_mdp_comp.c b/drivers/media/platform/mtk-mdp/mtk_mdp_comp.c
> index 85ef274841a3..9527649de98e 100644
> --- a/drivers/media/platform/mtk-mdp/mtk_mdp_comp.c
> +++ b/drivers/media/platform/mtk-mdp/mtk_mdp_comp.c
> @@ -151,29 +151,50 @@ void mtk_mdp_comp_clock_off(struct mtk_mdp_comp *comp)
>  		mtk_smi_larb_put(comp->larb_dev);
>  }
>  
> -static int mtk_mdp_comp_bind(struct device *dev, struct device *master, void *data)
> +/*
> + * The MDP master device node is identified by the device tree alias
> + * "mdp-rdma0".
> + */
> +static bool is_mdp_master(struct device *dev)
> +{
> +	struct device_node *aliases, *mdp_rdma0_node;
> +	const char *mdp_rdma0_path;
> +
> +	if (!dev->of_node)
> +		return false;
> +
> +	aliases = of_find_node_by_path("/aliases");
> +	if (!aliases) {
> +		dev_err(dev, "no aliases found for mdp-rdma0");
> +		return false;
> +	}
> +
> +	mdp_rdma0_path = of_get_property(aliases, "mdp-rdma0", NULL);
> +	if (!mdp_rdma0_path) {
> +		dev_err(dev, "get mdp-rdma0 property of /aliases failed");
> +		return false;
> +	}
> +
> +	mdp_rdma0_node = of_find_node_by_path(mdp_rdma0_path);
> +	if (!mdp_rdma0_node) {
> +		dev_err(dev, "path resolution failed for %s", mdp_rdma0_path);
> +		return false;
> +	}
> +
> +	return dev->of_node == mdp_rdma0_node;


About how to determine the master mdp driver, we also can
judge the component type. The component type can be gotten by calling
of_device_get_match_data(dev). If the component is MTK_MDP_RDMA, it is
the master driver. No matter it is mdp_rdma0 or mdp_rdma1.
http://lists.infradead.org/pipermail/linux-mediatek/2021-August/028533.html

IMO, judging it by component type is more flexible because it does not
limit to 'mdp_rdma0'.

> +}
> +
> +static int mtk_mdp_comp_bind(struct device *dev, struct device *master,
> +			void *data)
>  {
>  	struct mtk_mdp_comp *comp = dev_get_drvdata(dev);
>  	struct mtk_mdp_dev *mdp = data;
> -	struct device_node *vpu_node;
>  
>  	mtk_mdp_register_component(mdp, comp);
>  
> -	/*
> -	 * If this component has a "mediatek-vpu" property, it is responsible for
> -	 * notifying the mdp master driver about it so it can be further initialized
> -	 * later.
> -	 */
> -	vpu_node = of_parse_phandle(dev->of_node, "mediatek,vpu", 0);
> -	if (vpu_node) {
> +	if (is_mdp_master(dev)) {
>  		int ret;
>  
> -		mdp->vpu_dev = of_find_device_by_node(vpu_node);
> -		if (WARN_ON(!mdp->vpu_dev)) {
> -			dev_err(dev, "vpu pdev failed\n");
> -			of_node_put(vpu_node);
> -		}
> -
>  		ret = v4l2_device_register(dev, &mdp->v4l2_dev);
>  		if (ret) {
>  			dev_err(dev, "Failed to register v4l2 device\n");
> @@ -187,9 +208,8 @@ static int mtk_mdp_comp_bind(struct device *dev, struct device *master, void *da
>  		}
>  
>  		/*
> -		 * presence of the "mediatek,vpu" property in a device node
> -		 * indicates that it is the primary MDP rdma device and MDP DMA
> -		 * ops should be handled by its DMA callbacks.
> +		 * MDP DMA ops will be handled by the DMA callbacks associated with this
> +		 * device;
>  		 */
>  		mdp->rdma_dev = dev;
>  	}
> diff --git a/drivers/media/platform/mtk-mdp/mtk_mdp_core.c b/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
> index 50eafcc9993d..6a775463399c 100644
> --- a/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
> +++ b/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
> @@ -150,8 +150,9 @@ static void release_of(struct device *dev, void *data)
>  
>  static int mtk_mdp_master_bind(struct device *dev)
>  {
> -	int status;
>  	struct mtk_mdp_dev *mdp = dev_get_drvdata(dev);
> +	struct device_node *vpu_node;
> +	int status;
>  
>  	status = component_bind_all(dev, mdp);
>  	if (status) {
> @@ -159,15 +160,30 @@ static int mtk_mdp_master_bind(struct device *dev)
>  		goto err_component_bind_all;
>  	}
>  
> -	if (mdp->vpu_dev) {
> -		int ret = vpu_wdt_reg_handler(mdp->vpu_dev, mtk_mdp_reset_handler, mdp,
> -					  VPU_RST_MDP);
> -		if (ret) {
> -			dev_err(dev, "Failed to register reset handler\n");
> -			goto err_wdt_reg;
> -		}
> -	} else {
> -		dev_err(dev, "no vpu_dev found\n");
> +	if (mdp->rdma_dev == NULL) {
> +		dev_err(dev, "Primary MDP device not found");
> +		status = -ENODEV;
> +		goto err_component_bind_all;
> +	}
> +
> +	vpu_node = of_find_node_by_name(NULL, "vpu");
> +	if (!vpu_node) {
> +		dev_err(dev, "unable to find vpu node");
> +		status = -ENODEV;
> +		goto err_wdt_reg;
> +	}
> +
> +	mdp->vpu_dev = of_find_device_by_node(vpu_node);

The 'vpu_node' should be put by calling 'of_node_put(vpu_node)' when it
is not used.

> +	if (!mdp->vpu_dev) {
> +		dev_err(dev, "unable to find vpu device");
> +		status = -ENODEV;
> +		goto err_wdt_reg;
> +	}
> +
> +	status = vpu_wdt_reg_handler(mdp->vpu_dev, mtk_mdp_reset_handler, mdp, VPU_RST_MDP);
> +	if (status) {
> +		dev_err(dev, "Failed to register reset handler\n");
> +		goto err_wdt_reg;
>  	}
>  
>  	status = mtk_mdp_register_m2m_device(mdp);