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Date: Mon, 25 Oct 2021 13:05:25 -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 v2 1/2] drm/bridge: parade-ps8640: Enable runtime power management
Quoting Philip Chen (2021-10-21 14:05:59)
> 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.
>
> 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 dalay
s/dalay/delay/
> to fit into this driver change.
>
> Besides, rename "powered" to "pre_enabled" and don't check for it in
"Besides" doesn't make sense here. Probably "In addition" or "Also"?
> 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>
> ---
> diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
> index 3aaa90913bf8..220ca3b03d24 100644
> --- a/drivers/gpu/drm/bridge/parade-ps8640.c
> +++ b/drivers/gpu/drm/bridge/parade-ps8640.c
> @@ -148,6 +149,25 @@ static inline struct ps8640 *aux_to_ps8640(struct drm_dp_aux *aux)
> return container_of(aux, struct ps8640, aux);
> }
>
> +static void ps8640_ensure_hpd(struct ps8640 *ps_bridge)
> +{
> + 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", ret);
Missing newline on the print message.
> +}
> +
> static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux,
> struct drm_dp_aux_msg *msg)
> {
> @@ -171,6 +191,9 @@ static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux,
> if (msg->address & ~SWAUX_ADDR_MASK)
> return -EINVAL;
>
> + pm_runtime_get_sync(dev);
> + ps8640_ensure_hpd(ps_bridge);
Shouldn't we bail out of here with an error if we can't ensure hpd?
> +
> switch (request) {
> case DP_AUX_NATIVE_WRITE:
> case DP_AUX_NATIVE_READ:
> @@ -180,14 +203,15 @@ static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux,
> case DP_AUX_I2C_READ:
> break;
> default:
> - return -EINVAL;
> + ret = -EINVAL;
> + goto exit;
> }
>
> ret = regmap_write(map, PAGE0_AUXCH_CFG3, AUXCH_CFG3_RESET);
> if (ret) {
> DRM_DEV_ERROR(dev, "failed to write PAGE0_AUXCH_CFG3: %d\n",
> ret);
> - return ret;
> + goto exit;
> }
>
> /* Assume it's good */
> @@ -213,7 +237,7 @@ static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux,
> DRM_DEV_ERROR(dev,
> "failed to write WDATA: %d\n",
> ret);
> - return ret;
> + goto exit;
> }
> }
> }
> @@ -228,7 +252,7 @@ static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux,
> if (ret) {
> DRM_DEV_ERROR(dev, "failed to read PAGE0_SWAUX_STATUS: %d\n",
> ret);
> - return ret;
> + goto exit;
> }
>
> switch (data & SWAUX_STATUS_MASK) {
> @@ -250,9 +274,11 @@ static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux,
> len = data & SWAUX_M_MASK;
> break;
> case SWAUX_STATUS_INVALID:
> - return -EOPNOTSUPP;
> + ret = -EOPNOTSUPP;
> + goto exit;
> case SWAUX_STATUS_TIMEOUT:
> - return -ETIMEDOUT;
> + ret = -ETIMEDOUT;
> + goto exit;
> }
>
> if (len && (request == DP_AUX_NATIVE_READ ||
It may be simpler to understand the diff if the transfer function still
exited the same way and a small wrapper function was put around this to
do the runtime PM operations.
pm_runtime_get_sync();
if (ps8640_hpd_asserted())
ret = ps8640_aux_transfer_msg();
pm_runtime_mark_last_busy();
pm_runtime_put_autosuspend();
return ret;
> @@ -587,6 +611,13 @@ static int ps8640_probe(struct i2c_client *client)
> ps_bridge->aux.transfer = ps8640_aux_transfer;
> drm_dp_aux_init(&ps_bridge->aux);
>
> + pm_runtime_enable(dev);
> + pm_runtime_set_autosuspend_delay(dev, 500);
Presumably 500 is chosen because the message transfer speed is faster
than that? Can we get a comment in the code for that?
> + pm_runtime_use_autosuspend(dev);
> + ret = devm_add_action_or_reset(dev, ps8640_runtime_disable, dev);
> + if (ret)
> + return ret;
> +
> drm_bridge_add(&ps_bridge->bridge);
>
> return 0;
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