Re: [PATCH 2/3] usb: typec: fsa4480: Add support to swap SBU orientation

["Luca Weiss" <luca.weiss@fairphone.com>]

On Tue Oct 17, 2023 at 11:01 AM CEST, Heikki Krogerus wrote:
> Hi Luca,
>
> On Fri, Oct 13, 2023 at 01:38:06PM +0200, Luca Weiss wrote:
> > On some hardware designs the AUX+/- lanes are connected reversed to
> > SBU1/2 compared to the expected design by FSA4480.
> > 
> > Made more complicated, the otherwise compatible Orient-Chip OCP96011
> > expects the lanes to be connected reversed compared to FSA4480.
> > 
> > * FSA4480 block diagram shows AUX+ connected to SBU2 and AUX- to SBU1.
> > * OCP96011 block diagram shows AUX+ connected to SBU1 and AUX- to SBU2.
> > 
> > So if OCP96011 is used as drop-in for FSA4480 then the orientation
> > handling in the driver needs to be reversed to match the expectation of
> > the OCP96011 hardware.
> > 
> > Support parsing the data-lanes parameter in the endpoint node to swap
> > this in the driver.
> > 
> > The parse_data_lanes_mapping function is mostly taken from nb7vpq904m.c.
> > 
> > Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
> > ---
> >  drivers/usb/typec/mux/fsa4480.c | 81 +++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 81 insertions(+)
> > 
> > diff --git a/drivers/usb/typec/mux/fsa4480.c b/drivers/usb/typec/mux/fsa4480.c
> > index e0ee1f621abb..6ee467c96fb6 100644
> > --- a/drivers/usb/typec/mux/fsa4480.c
> > +++ b/drivers/usb/typec/mux/fsa4480.c
> > @@ -9,6 +9,7 @@
> >  #include <linux/kernel.h>
> >  #include <linux/module.h>
> >  #include <linux/mutex.h>
> > +#include <linux/of_graph.h>
>
> If you don't mind, let's keep this driver ready for ACPI, just in
> case...

I'm quite clueless about any details about ACPI but makes sense to use
the generic APIs.

>
> >  #include <linux/regmap.h>
> >  #include <linux/usb/typec_dp.h>
> >  #include <linux/usb/typec_mux.h>
> > @@ -60,6 +61,7 @@ struct fsa4480 {
> >  	unsigned int svid;
> >  
> >  	u8 cur_enable;
> > +	bool swap_sbu_lanes;
> >  };
> >  
> >  static const struct regmap_config fsa4480_regmap_config = {
> > @@ -76,6 +78,9 @@ static int fsa4480_set(struct fsa4480 *fsa)
> >  	u8 enable = FSA4480_ENABLE_DEVICE;
> >  	u8 sel = 0;
> >  
> > +	if (fsa->swap_sbu_lanes)
> > +		reverse = !reverse;
> > +
> >  	/* USB Mode */
> >  	if (fsa->mode < TYPEC_STATE_MODAL ||
> >  	    (!fsa->svid && (fsa->mode == TYPEC_MODE_USB2 ||
> > @@ -179,12 +184,84 @@ static int fsa4480_mux_set(struct typec_mux_dev *mux, struct typec_mux_state *st
> >  	return ret;
> >  }
> >  
> > +enum {
> > +	NORMAL_LANE_MAPPING,
> > +	INVERT_LANE_MAPPING,
> > +};
> > +
> > +#define DATA_LANES_COUNT	2
> > +
> > +static const int supported_data_lane_mapping[][DATA_LANES_COUNT] = {
> > +	[NORMAL_LANE_MAPPING] = { 0, 1 },
> > +	[INVERT_LANE_MAPPING] = { 1, 0 },
> > +};
> > +
> > +static int fsa4480_parse_data_lanes_mapping(struct fsa4480 *fsa)
> > +{
> > +	struct device_node *ep;
>
>         struct fwnode_handle *ep;
>
> > +	u32 data_lanes[DATA_LANES_COUNT];
> > +	int ret, i, j;
> > +
> > +	ep = of_graph_get_next_endpoint(fsa->client->dev.of_node, NULL);
>
> Shouldn't you loop through the endpoints? In any case:
>
>         ep = fwnode_graph_get_next_endpoint(dev_fwnode(&fsa->client->dev, NULL));

The docs only mention one endpoint so I'm assuming just next_endpoint is
fine?

>
> > +	if (!ep)
> > +		return 0;
> > +
> > +	ret = of_property_count_u32_elems(ep, "data-lanes");
>
>         ret = fwnode_property_count_u32(ep, "data-lanes");
>
> But is this necessary at all in this case - why not just read the
> array since you expect a fixed size for it (if the read fails it fails)?

Hm yeah that should be okay.. Will check the docs
of_property_read_u32_array (or well fwnode_property_read_u32_array) to
see if there's any gotchas if there's less or more elements provided.

Regards
Luca

>
> > +	if (ret == -EINVAL)
> > +		/* Property isn't here, consider default mapping */
> > +		goto out_done;
> > +	if (ret < 0)
> > +		goto out_error;
> > +
> > +	if (ret != DATA_LANES_COUNT) {
> > +		dev_err(&fsa->client->dev, "expected 2 data lanes\n");
> > +		ret = -EINVAL;
> > +		goto out_error;
> > +	}
> > +
> > +	ret = of_property_read_u32_array(ep, "data-lanes", data_lanes, DATA_LANES_COUNT);
>
>         ret = fwnode_property_read_u32_array(ep, "data-lanes", data_lanes, DATA_LANES_COUNT);
>
> > +	if (ret)
> > +		goto out_error;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(supported_data_lane_mapping); i++) {
> > +		for (j = 0; j < DATA_LANES_COUNT; j++) {
> > +			if (data_lanes[j] != supported_data_lane_mapping[i][j])
> > +				break;
> > +		}
> > +
> > +		if (j == DATA_LANES_COUNT)
> > +			break;
> > +	}
> > +
> > +	switch (i) {
> > +	case NORMAL_LANE_MAPPING:
> > +		break;
> > +	case INVERT_LANE_MAPPING:
> > +		fsa->swap_sbu_lanes = true;
> > +		dev_info(&fsa->client->dev, "using inverted data lanes mapping\n");
>
> That is just noise. Please drop it.
>
> > +		break;
> > +	default:
> > +		dev_err(&fsa->client->dev, "invalid data lanes mapping\n");
> > +		ret = -EINVAL;
> > +		goto out_error;
> > +	}
> > +
> > +out_done:
> > +	ret = 0;
> > +
> > +out_error:
> > +	of_node_put(ep);
> > +
> > +	return ret;
> > +}
> > +
> >  static int fsa4480_probe(struct i2c_client *client)
> >  {
> >  	struct device *dev = &client->dev;
> >  	struct typec_switch_desc sw_desc = { };
> >  	struct typec_mux_desc mux_desc = { };
> >  	struct fsa4480 *fsa;
> > +	int ret;
> >  
> >  	fsa = devm_kzalloc(dev, sizeof(*fsa), GFP_KERNEL);
> >  	if (!fsa)
> > @@ -193,6 +270,10 @@ static int fsa4480_probe(struct i2c_client *client)
> >  	fsa->client = client;
> >  	mutex_init(&fsa->lock);
> >  
> > +	ret = fsa4480_parse_data_lanes_mapping(fsa);
> > +	if (ret)
> > +		return ret;
> > +
> >  	fsa->regmap = devm_regmap_init_i2c(client, &fsa4480_regmap_config);
> >  	if (IS_ERR(fsa->regmap))
> >  		return dev_err_probe(dev, PTR_ERR(fsa->regmap), "failed to initialize regmap\n");
> > 
> > -- 
> > 2.42.0