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

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Message-ID: <CAE-0n50C82He9KCyXRTQGwQxqS6CWhm3w6Vv-5ayKYEfZyt-jg@mail.gmail.com>
Date:   Tue, 26 Oct 2021 12:36:24 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     LKML <linux-kernel@...r.kernel.org>,
        Philip Chen <philipchen@...omium.org>
Cc:     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

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?

> +{
> +       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>