Re: [PATCH v3 3/3] media: mtk-mdp: Fix mdp device tree

[Matthias Brugger]

On 15/05/17 04:31, Minghsiu Tsai wrote:
> On Fri, 2017-05-12 at 17:05 +0200, Matthias Brugger wrote:
> > On 12/05/17 05:22, Minghsiu Tsai wrote:
> > > From: Daniel Kurtz <djkurtz@xxxxxxxxxxxx>
> > >
> > > If the mdp_* nodes are under an mdp sub-node, their corresponding
> > > platform device does not automatically get its iommu assigned properly.
> > >
> > > Fix this by moving the mdp component nodes up a level such that they are
> > > siblings of mdp and all other SoC subsystems.  This also simplifies the
> > > device tree.
> > >
> > > Although it fixes iommu assignment issue, it also break compatibility
> > > with old device tree. So, the patch in driver is needed to iterate over
> > > sibling mdp device nodes, not child ones, to keep driver work properly.
> >
> > Couldn't we preserve backwards compatibility by doing something like this:
> > diff --git a/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
> > b/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
> > index 9e4eb7dcc424..277d8fe6eb76 100644
> > --- a/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
> > +++ b/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
> > @@ -103,7 +103,7 @@ static int mtk_mdp_probe(struct platform_device *pdev)
> >    {
> >    	struct mtk_mdp_dev *mdp;
> >    	struct device *dev = &pdev->dev;
> > -	struct device_node *node;
> > +	struct device_node *node, *parent;
> >    	int i, ret = 0;
> >
> >    	mdp = devm_kzalloc(dev, sizeof(*mdp), GFP_KERNEL);
> > @@ -117,8 +117,14 @@ static int mtk_mdp_probe(struct platform_device *pdev)
> >    	mutex_init(&mdp->lock);
> >    	mutex_init(&mdp->vpulock);
> >
> > +	/* Old dts had the components as child nodes */
> > +	if (of_get_next_child(dev->of_node, NULL))
> > +		parent = dev->of_node;
> > +	else
> > +		parent = dev->of_node->parent;
> > +
> >    	/* Iterate over sibling MDP function blocks */
> > -	for_each_child_of_node(dev->of_node, node) {
> > +	for_each_child_of_node(parent, node) {
> >    		const struct of_device_id *of_id;
> >    		enum mtk_mdp_comp_type comp_type;
> >    		int comp_id;
> >
> > Maybe even by putting a warning in the if branch to make sure, people
> > are aware of their out-of-date device tree blobs.
> >
> > Regards,
> > Matthias
>
> Hi Matthias,
>
> It is a good idea to do compatible in such a way and put a warning the
> device tree is out of date. People can find out cause soon if device
> tree is old.
>
> I modify the code as below:
>
> +	/* Old dts had the components as child nodes */
> +	if (of_get_next_child(dev->of_node, NULL)) {
> +		parent = dev->of_node;
> +		dev_warn(dev, "device tree is out of date\n");
> +	} else {
> +		parent = dev->of_node->parent;
> +	}
>
> Will you upload it in a separate patch?
> If not, I can merge it in my patch series and upload v4.

Please integrate it into your patch series.

Mauro, are you ok with the dev_warn about the out-of-date device-tree?

Regards,
Matthias


> Best Regards,
>
> Ming Hsiu
>
> > > Signed-off-by: Daniel Kurtz <djkurtz@xxxxxxxxxxxx>
> > > Signed-off-by: Minghsiu Tsai <minghsiu.tsai@xxxxxxxxxxxx>
> > >
> > > ---
> > >    drivers/media/platform/mtk-mdp/mtk_mdp_core.c | 2 +-
> > >    1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/media/platform/mtk-mdp/mtk_mdp_core.c b/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
> > > index 9e4eb7d..a5ad586 100644
> > > --- a/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
> > > +++ b/drivers/media/platform/mtk-mdp/mtk_mdp_core.c
> > > @@ -118,7 +118,7 @@ static int mtk_mdp_probe(struct platform_device *pdev)
> > >    	mutex_init(&mdp->vpulock);
> > >    
> > >    	/* Iterate over sibling MDP function blocks */
> > > -	for_each_child_of_node(dev->of_node, node) {
> > > +	for_each_child_of_node(dev->of_node->parent, node) {
> > >    		const struct of_device_id *of_id;
> > >    		enum mtk_mdp_comp_type comp_type;
> > >    		int comp_id;