Re: [PATCH] phy: ti: gmii-sel: Allow parent to not be syscon node

[Andrew Davis]

On 5/15/23 11:05 PM, Siddharth Vadapalli wrote:
> Andrew,
>
> On 16/05/23 01:29, Andrew Davis wrote:
> > If the parent node is not a syscon type, then fallback and check
> > if we can get a regmap from our own node. This no longer forces
> > us to make the parent of this node a syscon node when that might
> > not be appropriate.
>
> Could you please let me know in which cases it is appropriate versus in which
> cases it isn't?

Use of syscon nodes should be discouraged, in most cases they can and should be
avoided. The only time we would need to have a syscon parent is when the register
space contains multiple sub-devices with bit level interleaving.

Most devices should never need syscon, we overuse syscon due to driver like
this that have no other option than to make the parent device a syscon node.

> Is syscon_node_to_regmap() being retained for backward
> compatibility until the device-tree nodes are cleaned up across all devices?

Yes, the old way is left only for backwards compatibility.

> > Signed-off-by: Andrew Davis <afd@xxxxxx>
> > ---
> >   drivers/phy/ti/phy-gmii-sel.c | 9 ++++++---
> >   1 file changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/phy/ti/phy-gmii-sel.c b/drivers/phy/ti/phy-gmii-sel.c
> > index 8c667819c39a..1e67ed9a5cf6 100644
> > --- a/drivers/phy/ti/phy-gmii-sel.c
> > +++ b/drivers/phy/ti/phy-gmii-sel.c
> > @@ -435,9 +435,12 @@ static int phy_gmii_sel_probe(struct platform_device *pdev)
> >   
> >   	priv->regmap = syscon_node_to_regmap(node->parent);
> >   	if (IS_ERR(priv->regmap)) {
> > -		ret = PTR_ERR(priv->regmap);
> > -		dev_err(dev, "Failed to get syscon %d\n", ret);
> > -		return ret;
> > +		priv->regmap = device_node_to_regmap(node);
>
> If device_node_to_regmap() can always be used with the corresponding changes
> made to the device-tree nodes, wouldn't it be better to use it directly instead
> of using it as a fallback? (This is based on the assumption that
> syscon_node_to_regmap() is only being retained until the device-tree nodes are
> cleaned up to work with device_node_to_regmap()).

Yes, that could work too. I was trying to make the minimal changes here, but
if we feel it works better we can have the default be to check the self node first.

Andrew

> > +		if (IS_ERR(priv->regmap)) {
> > +			ret = PTR_ERR(priv->regmap);
> > +			dev_err(dev, "Failed to get syscon %d\n", ret);
> > +			return ret;
> > +		}
> >   	}
> >   
> >   	ret = phy_gmii_sel_init_ports(priv);