Re: [PATCH v6 7/7] drm/bridge: it6505: Register Type C mode switches

[Pin-yen Lin <treapking@chromium.org>]

Hi Andy,

Thanks for reviewing the patch.

On Thu, Nov 24, 2022 at 8:23 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Thu, Nov 24, 2022 at 06:20:56PM +0800, Pin-yen Lin wrote:
> > Register USB Type-C mode switches when the "mode-switch" property and
> > relevant port are available in Device Tree. Configure the "lane_swap"
> > state based on the entered alternate mode for a specific Type-C
> > connector, which ends up updating the lane swap registers of the it6505
> > chip.
>
> ...
>
> >  config DRM_ITE_IT6505
> >          tristate "ITE IT6505 DisplayPort bridge"
> >          depends on OF
> > +     depends on TYPEC || TYPEC=n
> >       select DRM_DISPLAY_DP_HELPER
> >       select DRM_DISPLAY_HDCP_HELPER
> >       select DRM_DISPLAY_HELPER
>
> Something went wrong with the indentation. Perhaps you need to fix it first.
>
> ...
>
> >  #include <drm/drm_edid.h>
> >  #include <drm/drm_print.h>
> >  #include <drm/drm_probe_helper.h>
> > +#include <drm/drm_of.h>
>
> Make it ordered?

Will fix it in v7.

>
> ...
>
> > +struct it6505_port_data {
>
> > +     bool dp_connected;
>
> Perhaps make it last?

Will fix it in v7.

>
> > +     struct typec_mux_dev *typec_mux;
> > +     struct it6505 *it6505;
> > +};
>
> ...
>
> > +static void it6505_typec_ports_update(struct it6505 *it6505)
> > +{
> > +     usleep_range(3000, 4000);
> > +
> > +     if (it6505->typec_ports[0].dp_connected && it6505->typec_ports[1].dp_connected)
> > +             /* Both ports available, do nothing to retain the current one. */
> > +             return;
> > +     else if (it6505->typec_ports[0].dp_connected)
> > +             it6505->lane_swap = false;
> > +     else if (it6505->typec_ports[1].dp_connected)
> > +             it6505->lane_swap = true;
> > +
> > +     usleep_range(3000, 4000);
> > +}
>
> As per previous patch comments.

Will update it in v7.

>
> Also, comment out these long sleeps. Why they are needed.

Actually, it turns out that these sleeps are not needed. I'll remove it in v7.

>
> ...
>
> > +             int ret = pm_runtime_get_sync(dev);
> > +
> > +             /*
> > +              * On system resume, mux_set can be triggered before
> > +              * pm_runtime_force_resume re-enables runtime power management.
>
> We refer to the functions as func().

Will fix this in v7.

>
> > +              * Handling the error here to make sure the bridge is powered on.
> > +              */
> > +             if (ret < 0)
> > +                     it6505_poweron(it6505);
>
> This seems needed a bit more of explanation, esp. why you leave PM runtime
> reference count bumped up.

pm_runtime_force_suspend() disables runtime PM when the device enters
suspend, and sometime it6505_typec_mux_set() is called before
pm_runtime_force_resume brings runtime PM back. We force power up the
bridge in this case and leave the ref count incremented to make the
future pm_runtime_(get|put)_sync() calls balanced.

I'll include more explanations around this in v7.

>
> ...
>
> > +     num_lanes = drm_of_get_data_lanes_count(node, 0, 2);
> > +     if (num_lanes <= 0) {
> > +             dev_err(dev, "Error on getting data lanes count: %d\n",
> > +                     num_lanes);
> > +             return num_lanes;
> > +     }
> > +
> > +     ret = of_property_read_u32_array(node, "data-lanes", dp_lanes, num_lanes);
> > +     if (ret) {
> > +             dev_err(dev, "Failed to read the data-lanes variable: %d\n",
> > +                     ret);
> > +             return ret;
> > +     }
> > +
> > +     for (i = 0; i < num_lanes; i++) {
> > +             if (port_num != -1 && port_num != dp_lanes[i] / 2) {
> > +                     dev_err(dev, "Invalid data lane numbers\n");
> > +                     return -EINVAL;
> > +             }
>
> As per previous patch comments.

I'll remove this part in v7 and try to figure out how to do similar
checking with schemas.
>
> > +             port_num = dp_lanes[i] / 2;
> > +     }
>
> The above seems like tons of duplicating code that drivers need to implement.
> Can we shrink that burden by adding some library functions?

Could you advise where this lib file should go, and what the namings
can be? The "port-switching" logic is specific to some of the DP
bridges, and I'm not sure what kinds of naming/structure fit into this
case.

Thanks and regards,
Pin-yen

>
> --
> With Best Regards,
> Andy Shevchenko
>
>