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From:   Philip Chen <philipchen@chromium.org>
Date:   Thu, 9 Sep 2021 11:15:27 -0700
Message-ID: <CA+cxXhnPd1Z_HVjgM8b0wskASF-ZGuvYDh0quiVMwKFhKVx-JA@mail.gmail.com>
Subject: Re: [PATCH 2/2] drm/bridge: parade-ps8640: Add support for AUX channel
To:     Stephen Boyd <swboyd@chromium.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Douglas Anderson <dianders@chromium.org>,
        Andrzej Hajda <a.hajda@samsung.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@linux.ie>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Jonas Karlman <jonas@kwiboo.se>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Robert Foss <robert.foss@linaro.org>,
        dri-devel <dri-devel@lists.freedesktop.org>
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Hi,

On Wed, Sep 8, 2021 at 3:27 PM Stephen Boyd <swboyd@chromium.org> wrote:
>
> Quoting Philip Chen (2021-09-08 11:18:06)
> > diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
> > index a16725dbf912..3f0241a60357 100644
> > --- a/drivers/gpu/drm/bridge/parade-ps8640.c
> > +++ b/drivers/gpu/drm/bridge/parade-ps8640.c
> > @@ -93,6 +115,102 @@ static inline struct ps8640 *bridge_to_ps8640(struct drm_bridge *e)
> >         return container_of(e, struct ps8640, bridge);
> >  }
> >
> > +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)
> > +{
> > +       struct ps8640 *ps_bridge = aux_to_ps8640(aux);
> > +       struct i2c_client *client = ps_bridge->page[PAGE0_DP_CNTL];
> > +       struct regmap *map = ps_bridge->regmap[PAGE0_DP_CNTL];
> > +       unsigned int len = msg->size;
> > +       unsigned int data;
> > +       int ret;
> > +       u8 request = msg->request &
> > +                    ~(DP_AUX_I2C_MOT | DP_AUX_I2C_WRITE_STATUS_UPDATE);
> > +       u8 *buf = msg->buffer;
> > +       bool is_native_aux = false;
> > +
> > +       if (len > DP_AUX_MAX_PAYLOAD_BYTES)
> > +               return -EINVAL;
> > +
> > +       pm_runtime_get_sync(&client->dev);
>
> Is this driver using runtime PM? Probably can't add this until it is
> actually runtime PM enabled.
Thanks - I think this driver doesn't enable runtime PM yet.
I'll remove all of the pm_runtime_* calls for now.
>
> > +
> > +       switch (request) {
> > +       case DP_AUX_NATIVE_WRITE:
> > +       case DP_AUX_NATIVE_READ:
> > +               is_native_aux = true;
> > +       case DP_AUX_I2C_WRITE:
> > +       case DP_AUX_I2C_READ:
> > +               regmap_write(map, PAGE0_AUXCH_CFG3, AUXCH_CFG3_RESET);
> > +               break;
> > +       default:
> > +               ret = -EINVAL;
> > +               goto exit;
> > +       }
> > +
> > +       /* Assume it's good */
> > +       msg->reply = 0;
> > +
> > +       data = ((request << 4) & AUX_CMD_MASK) |
> > +              ((msg->address >> 16) & AUX_ADDR_19_16_MASK);
> > +       regmap_write(map, PAGE0_AUX_ADDR_23_16, data);
> > +       data = (msg->address >> 8) & 0xff;
> > +       regmap_write(map, PAGE0_AUX_ADDR_15_8, data);
> > +       data = msg->address & 0xff;
> > +       regmap_write(map, PAGE0_AUX_ADDR_7_0, msg->address & 0xff);
>
> Can we pack this into a three byte buffer and write it in one
> regmap_bulk_write()? That would be nice because it looks like the
> addresses are all next to each other in the i2c address space.
Sure, I will address this in the next version.
>
> > +
> > +       data = (len - 1) & AUX_LENGTH_MASK;
> > +       regmap_write(map, PAGE0_AUX_LENGTH, data);
> > +
> > +       if (request == DP_AUX_NATIVE_WRITE || request == DP_AUX_I2C_WRITE) {
> > +               ret = regmap_noinc_write(map, PAGE0_AUX_WDATA, buf, len);
> > +               if (ret < 0) {
> > +                       DRM_ERROR("failed to write PAGE0_AUX_WDATA");
>
> Needs a newline.
Adding an empty line here doesn't look like a common Linux style?
Could you point me to any similar instances in the Linux codebase?
>
> > +                       goto exit;
> > +               }
> > +       }
> > +
> > +       regmap_write(map, PAGE0_AUX_CTRL, AUX_START);
> > +
> > +       regmap_read(map, PAGE0_AUX_STATUS, &data);
> > +       switch (data & AUX_STATUS_MASK) {
> > +       case AUX_STATUS_DEFER:
> > +               if (is_native_aux)
> > +                       msg->reply |= DP_AUX_NATIVE_REPLY_DEFER;
> > +               else
> > +                       msg->reply |= DP_AUX_I2C_REPLY_DEFER;
> > +               goto exit;
> > +       case AUX_STATUS_NACK:
> > +               if (is_native_aux)
> > +                       msg->reply |= DP_AUX_NATIVE_REPLY_NACK;
> > +               else
> > +                       msg->reply |= DP_AUX_I2C_REPLY_NACK;
> > +               goto exit;
> > +       case AUX_STATUS_TIMEOUT:
> > +               ret = -ETIMEDOUT;
> > +               goto exit;
> > +       }
> > +
> > +       if (request == DP_AUX_NATIVE_READ || request == DP_AUX_I2C_READ) {
> > +               ret = regmap_noinc_read(map, PAGE0_AUX_RDATA, buf, len);
> > +               if (ret < 0)
> > +                       DRM_ERROR("failed to read PAGE0_AUX_RDATA");
>
> Needs a newline.
>
> > +       }
> > +
> > +exit:
> > +       pm_runtime_mark_last_busy(&client->dev);
> > +       pm_runtime_put_autosuspend(&client->dev);
> > +
> > +       if (ret)
> > +               return ret;
> > +
> > +       return len;
> > +}
> > +
> >  static int ps8640_bridge_vdo_control(struct ps8640 *ps_bridge,
> >                                      const enum ps8640_vdo_control ctrl)
> >  {