Hi, On Wednesday 23 October 2013 08:12 PM, Matt Porter wrote: > On Tue, Oct 22, 2013 at 04:38:52PM -0500, Rob Herring wrote: >> On 10/22/2013 06:25 AM, Matt Porter wrote: >>> On Tue, Oct 22, 2013 at 12:48:29PM +0200, Matthijs Kooijman wrote: >>>> Hi Kishon, >>>> >>>> On Mon, Oct 21, 2013 at 02:57:26PM +0530, Kishon Vijay Abraham I wrote: >>>>> I think it makes sense to keep the data width property in the dwc2 node itself. >>>>> I mean it describes how the dwc2 IP is configured in that particular SoC (given >>>>> that it can be either <8> or <16>). >>>> If I'm reading the RT3052 datasheet correctly (GHWCFG4 register), the IP >>>> can be configured for 8, 16 or 8 _and_ 16. In the latter case, the "8 >>>> and 16 supported" would make sense as a property of dwc2 (though this >>>> value should be autodetectable through GHWCFG4), while the actual 8 or >>>> 16 supported by the PHY would make sense as property of a phy. >>> >>> There would be no value in adding a property for an already detectable >>> value to dwc2's binding. To be honest, it's pretty much useless >>> information due to the existence of the "8 and 16" option. >>> >>>> Note sure if this is really useful in practice as well, or if just >>>> setting the actual width to use on dwc2 makes more sense... >>> >>> The GHWCFG4 information itself is not useful in practice, as described >>> in the original thread: https://lkml.org/lkml/2013/10/10/477 >>> >>> It's certainly useful in practice to have this width property in either >>> the dwc2 or the phy binding. One can make a case for either. As I >>> mentioned in the original post, if we put it in the phy binding we'll be >>> updating the generic phy binding. We'll then need an api added into the >>> generic phy framework to fetch the width of a phy. >>> >>> Both cases are doable and trivial, we just need the canonical decision >>> from a DT maintainer as to where the property belongs. Given that they >>> are in ARM ksummit, I'm not expecting to hear anything right this >>> moment. :) >> >> The host can support both, so it is not a property of the host and is a >> property of the phy. It is no different than what mode a SPI slave >> requires or whether an i2c slave supports 8 or 10-bit addressing. Those >> examples are all 1 to many rather than 1 to 1 where it doesn't really >> matter, but the same logic applies. > > Makes good sense, thanks. > > In this case, given the PHY ownership of width, we can completely avoid > any DT properties. The generic phy compliant BCM Kona phy driver can > report via the generic phy framework that it is 8-bit wide. There's no > support for this type of thing now but it's pretty trivial to add. > > I went ahead and did a quick proof-of-concept that adds a free-form > phy attributes struct for the generic phy. Given that generic phys can > be for any transmission technology this could be filled with a jumble > unrelated and often unpopulated attributes over time. In any case, the > below patch allows the phy provider to choose to specify utmi_width and > a controller driver that cares can use phy_get_attrs() to fetch the > optional phy attributes and use the utmi_width field if applicable. > > Kishon: I'll start a separate thread to discuss what approach you'd like > to see in the generic phy framework to manage this. > > -Matt > > diff --git a/include/linux/phy/phy.h b/include/linux/phy/phy.h > index 6d72269..b763d7b 100644 > --- a/include/linux/phy/phy.h > +++ b/include/linux/phy/phy.h > @@ -38,6 +38,14 @@ struct phy_ops { > }; > > /** > + * struct phy_attrs - represents phy attributes > + * @utmi_width: Data path width implemented by UTMI PHY > + */ > +struct phy_attrs { > + int utmi_width; > +}; > + > +/** > * struct phy - represents the phy device > * @dev: phy device > * @id: id of the phy device > @@ -51,6 +59,7 @@ struct phy { > struct device dev; > int id; > const struct phy_ops *ops; > + struct phy_attrs *attrs; > struct phy_init_data *init_data; > struct mutex mutex; > int init_count; > @@ -127,6 +136,9 @@ int phy_init(struct phy *phy); > int phy_exit(struct phy *phy); > int phy_power_on(struct phy *phy); > int phy_power_off(struct phy *phy); > +static inline struct phy_attrs *phy_get_attrs(struct phy *phy) { > + return phy->attrs; > +}; I'd prefer to have phy_set_bus_width and phy_get_bus_width instead. Thanks Kishon > struct phy *phy_get(struct device *dev, const char *string); > struct phy *devm_phy_get(struct device *dev, const char *string); > void phy_put(struct phy *phy); > -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
