Re: [PATCH v6 10/11] drm/mediatek: dp: Add .wait_hpd_asserted() for AUX bus

[CK Hu (胡俊光)]

Hi, Angelo:

On Mon, 2023-07-17 at 16:14 +0200, AngeloGioacchino Del Regno wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  In order to support usecases in which the panel regulator can be
> switched on and off to save power, and usecases in which the panel
> regulator is off at boot, add a .wait_hpd_asserted() callback for
> the AUX bus: this will make sure to wait until the panel is fully
> ready after power-on before trying to communicate with it.
> 
> Also, parse the eDP display capabilities in that callback, so that
> we can also avoid using the .get_edid() callback from this bridge.
> 
> Since at this point the hpd machinery is performed in the new hpd
> callback and the detection and edid reading are done outside of
> this driver, assign the DRM_BRIDGE_OP_{DETECT, EDID, HPD} ops and
> register the bridge unconditionally at probe time only if we are
> probing full DisplayPort and not eDP while, for the latter, we
> register the bridge in the .done_probing() callback and only if
> the panel was found and triggered HPD.

Reviewed-by: CK Hu <ck.hu@xxxxxxxxxxxx>

> 
> Signed-off-by: AngeloGioacchino Del Regno <
> angelogioacchino.delregno@xxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/mediatek/mtk_dp.c | 45 ++++++++++++++++++++++++++---
> --
>  1 file changed, 38 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c
> b/drivers/gpu/drm/mediatek/mtk_dp.c
> index acdd457b5449..e74295ba9707 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dp.c
> @@ -1920,6 +1920,31 @@ static irqreturn_t mtk_dp_hpd_event(int hpd,
> void *dev)
>  	return IRQ_WAKE_THREAD;
>  }
>  
> +static int mtk_dp_wait_hpd_asserted(struct drm_dp_aux *mtk_aux,
> unsigned long wait_us)
> +{
> +	struct mtk_dp *mtk_dp = container_of(mtk_aux, struct mtk_dp,
> aux);
> +	u32 val;
> +	int ret;
> +
> +	ret = regmap_read_poll_timeout(mtk_dp->regs,
> MTK_DP_TRANS_P0_3414,
> +				       val, !!(val &
> HPD_DB_DP_TRANS_P0_MASK),
> +				       wait_us / 100, wait_us);
> +	if (ret) {
> +		mtk_dp->train_info.cable_plugged_in = false;
> +		return ret;
> +	}
> +
> +	mtk_dp->train_info.cable_plugged_in = true;
> +
> +	ret = mtk_dp_parse_capabilities(mtk_dp);
> +	if (ret) {
> +		drm_err(mtk_dp->drm_dev, "Can't parse capabilities\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
>  static int mtk_dp_dt_parse(struct mtk_dp *mtk_dp,
>  			   struct platform_device *pdev)
>  {
> @@ -2532,6 +2557,12 @@ static int mtk_dp_edp_link_panel(struct
> drm_dp_aux *mtk_aux)
>  		mtk_dp->next_bridge = NULL;
>  		return ret;
>  	}
> +
> +	/* For eDP, we add the bridge only if the panel was found */
> +	ret = devm_drm_bridge_add(dev, &mtk_dp->bridge);
> +	if (ret)
> +		return ret;
> +
>  	return 0;
>  }
>  
> @@ -2568,6 +2599,7 @@ static int mtk_dp_probe(struct platform_device
> *pdev)
>  	mtk_dp->aux.name = "aux_mtk_dp";
>  	mtk_dp->aux.dev = dev;
>  	mtk_dp->aux.transfer = mtk_dp_aux_transfer;
> +	mtk_dp->aux.wait_hpd_asserted = mtk_dp_wait_hpd_asserted;
>  	drm_dp_aux_init(&mtk_dp->aux);
>  
>  	spin_lock_init(&mtk_dp->irq_thread_lock);
> @@ -2600,15 +2632,8 @@ static int mtk_dp_probe(struct platform_device
> *pdev)
>  
>  	mtk_dp->bridge.funcs = &mtk_dp_bridge_funcs;
>  	mtk_dp->bridge.of_node = dev->of_node;
> -
> -	mtk_dp->bridge.ops =
> -		DRM_BRIDGE_OP_DETECT | DRM_BRIDGE_OP_EDID |
> DRM_BRIDGE_OP_HPD;
>  	mtk_dp->bridge.type = mtk_dp->data->bridge_type;
>  
> -	ret = devm_drm_bridge_add(dev, &mtk_dp->bridge);
> -	if (ret)
> -		return dev_err_probe(dev, ret, "Failed to add
> bridge\n");
> -
>  	mtk_dp->need_debounce = true;
>  	timer_setup(&mtk_dp->debounce_timer, mtk_dp_debounce_timer, 0);
>  
> @@ -2647,6 +2672,12 @@ static int mtk_dp_probe(struct platform_device
> *pdev)
>  				return ret;
>  			}
>  		}
> +	} else {
> +		mtk_dp->bridge.ops = DRM_BRIDGE_OP_DETECT |
> +				     DRM_BRIDGE_OP_EDID |
> DRM_BRIDGE_OP_HPD;
> +		ret = devm_drm_bridge_add(dev, &mtk_dp->bridge);
> +		if (ret)
> +			return dev_err_probe(dev, ret, "Failed to add
> bridge\n");
>  	}
>  
>  	pm_runtime_enable(dev);
> -- 
> 2.40.1