linux-kernel - Re: [PATCH v3 1/2] drm/bridge: parade-ps8640: Enable runtime power management

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Date:   Tue, 26 Oct 2021 14:28:44 -0700
From:   Philip Chen <philipchen@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, dianders@...omium.org,
        Andrzej Hajda <a.hajda@...sung.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Jonas Karlman <jonas@...boo.se>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v3 1/2] drm/bridge: parade-ps8640: Enable runtime power management

Hi

On Tue, Oct 26, 2021 at 12:36 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Philip Chen (2021-10-26 12:11:09)
> > Fit ps8640 driver into runtime power management framework:
> >
> > First, break _poweron() to 3 parts: (1) turn on power and wait for
> > ps8640's internal MCU to finish init (2) check panel HPD (which is
> > proxied by GPIO9) (3) the other configs. As runtime_resume() can be
> > called before panel is powered, we only add (1) to _resume() and leave
> > (2)(3) to _pre_enable(). We also add (2) to _aux_transfer() as we want
> > to ensure panel HPD is asserted before we start AUX CH transactions.
> >
> > Second, the original driver has a mysterious delay of 50 ms between (2)
> > and (3). Since Parade's support can't explain what the delay is for,
> > and we don't see removing the delay break any boards at hand, remove
> > the delay to fit into this driver change.
> >
> > In addition, rename "powered" to "pre_enabled" and don't check for it
> > in the pm_runtime calls. The pm_runtime calls are already refcounted
> > so there's no reason to check there. The other user of "powered",
> > _get_edid(), only cares if pre_enable() has already been called.
> >
> > Lastly, change some existing DRM_...() logging to dev_...() along the
> > way, since DRM_...() seem to be deprecated in [1].
> >
> > [1] https://patchwork.freedesktop.org/patch/454760/
> >
> > Signed-off-by: Philip Chen <philipchen@...omium.org>
> > Reviewed-by: Douglas Anderson <dianders@...omium.org>
> > ---
> >
> > Changes in v3:
> > - Fix typo/wording in the commit message.
> > - Add ps8640_aux_transfer_msg() for AUX operation. In
> >   ps8640_aux_transfer(), wrap around ps8640_aux_transfer_msg()
> >   with PM operations and HPD check.
> > - Document why autosuspend_delay is set to 500ms.
> >
> >  drivers/gpu/drm/bridge/parade-ps8640.c | 186 +++++++++++++++----------
> >  1 file changed, 115 insertions(+), 71 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
> > index 3aaa90913bf8..ac42a3473770 100644
> > --- a/drivers/gpu/drm/bridge/parade-ps8640.c
> > +++ b/drivers/gpu/drm/bridge/parade-ps8640.c
> > @@ -9,6 +9,7 @@
> >  #include <linux/i2c.h>
> >  #include <linux/module.h>
> >  #include <linux/of_graph.h>
> > +#include <linux/pm_runtime.h>
> >  #include <linux/regmap.h>
> >  #include <linux/regulator/consumer.h>
> >
> > @@ -100,7 +101,7 @@ struct ps8640 {
> >         struct regulator_bulk_data supplies[2];
> >         struct gpio_desc *gpio_reset;
> >         struct gpio_desc *gpio_powerdown;
> > -       bool powered;
> > +       bool pre_enabled;
> >  };
> >
> >  static const struct regmap_config ps8640_regmap_config[] = {
> > @@ -148,8 +149,29 @@ static inline struct ps8640 *aux_to_ps8640(struct drm_dp_aux *aux)
> >         return container_of(aux, struct ps8640, aux);
> >  }
> >
> > -static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux,
> > -                                  struct drm_dp_aux_msg *msg)
> > +static void ps8640_ensure_hpd(struct ps8640 *ps_bridge)
>
> static int ps8640_ensure_hpd?
Oops, this change was mis-added to the patch on top of this one.
I'll fix it in v4...

>
> > +{
> > +       struct regmap *map = ps_bridge->regmap[PAGE2_TOP_CNTL];
> > +       struct device *dev = &ps_bridge->page[PAGE2_TOP_CNTL]->dev;
> > +       int status;
> > +       int ret;
> > +
> > +       /*
> > +        * Apparently something about the firmware in the chip signals that
> > +        * HPD goes high by reporting GPIO9 as high (even though HPD isn't
> > +        * actually connected to GPIO9).
> > +        */
> > +       ret = regmap_read_poll_timeout(map, PAGE2_GPIO_H, status,
> > +                               status & PS_GPIO9, 20 * 1000, 200 * 1000);
> > +
> > +       if (ret < 0)
> > +               dev_warn(dev, "HPD didn't go high: %d\n", ret);
> > +
> > +       return ret;
> > +}
> > +
> > +static ssize_t ps8640_aux_transfer_msg(struct drm_dp_aux *aux,
> > +                                      struct drm_dp_aux_msg *msg)
> >  {
> >         struct ps8640 *ps_bridge = aux_to_ps8640(aux);
> >         struct regmap *map = ps_bridge->regmap[PAGE0_DP_CNTL];
>
> Otherwise
>
> Reviewed-by: Stephen Boyd <swboyd@...omium.org>