Re: [PATCH v7 11/11] drm/mediatek: dp: Don't register HPD interrupt handler for eDP case

[CK Hu (胡俊光)]

Hi, Angelo:

On Tue, 2023-07-25 at 09:32 +0200, AngeloGioacchino Del Regno wrote:
> The interrupt handler for HPD is useful only if a display is actually
> supposed to be hotpluggable, as that manages the machinery to perform
> cable (un)plug detection, debouncing and setup for re-training.
> 
> Since eDP panels are not supposed to be hotpluggable we can avoid
> using the HPD interrupts altogether and rely on HPD polling only
> for the suspend/resume case, saving us some spinlocking action and
> the overhead of interrupts firing at every suspend/resume cycle,
> achieving a faster (even if just slightly) display resume.

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

> 
> Signed-off-by: AngeloGioacchino Del Regno <
> angelogioacchino.delregno@xxxxxxxxxxxxx>
> Tested-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx>
> Reviewed-by: Alexandre Mergnat <amergnat@xxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/mediatek/mtk_dp.c | 73 +++++++++++++++++++--------
> ----
>  1 file changed, 46 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c
> b/drivers/gpu/drm/mediatek/mtk_dp.c
> index ba750d463e41..c06fcc7318e7 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dp.c
> @@ -2182,9 +2182,11 @@ static int mtk_dp_bridge_attach(struct
> drm_bridge *bridge,
>  
>  	mtk_dp->drm_dev = bridge->dev;
>  
> -	irq_clear_status_flags(mtk_dp->irq, IRQ_NOAUTOEN);
> -	enable_irq(mtk_dp->irq);
> -	mtk_dp_hwirq_enable(mtk_dp, true);
> +	if (mtk_dp->bridge.type != DRM_MODE_CONNECTOR_eDP) {
> +		irq_clear_status_flags(mtk_dp->irq, IRQ_NOAUTOEN);
> +		enable_irq(mtk_dp->irq);
> +		mtk_dp_hwirq_enable(mtk_dp, true);
> +	}
>  
>  	return 0;
>  
> @@ -2199,8 +2201,10 @@ static void mtk_dp_bridge_detach(struct
> drm_bridge *bridge)
>  {
>  	struct mtk_dp *mtk_dp = mtk_dp_from_bridge(bridge);
>  
> -	mtk_dp_hwirq_enable(mtk_dp, false);
> -	disable_irq(mtk_dp->irq);
> +	if (mtk_dp->bridge.type != DRM_MODE_CONNECTOR_eDP) {
> +		mtk_dp_hwirq_enable(mtk_dp, false);
> +		disable_irq(mtk_dp->irq);
> +	}
>  	mtk_dp->drm_dev = NULL;
>  	mtk_dp_poweroff(mtk_dp);
>  	drm_dp_aux_unregister(&mtk_dp->aux);
> @@ -2579,32 +2583,44 @@ static int mtk_dp_probe(struct
> platform_device *pdev)
>  	mtk_dp->dev = dev;
>  	mtk_dp->data = (struct mtk_dp_data
> *)of_device_get_match_data(dev);
>  
> -	mtk_dp->irq = platform_get_irq(pdev, 0);
> -	if (mtk_dp->irq < 0)
> -		return dev_err_probe(dev, mtk_dp->irq,
> -				     "failed to request dp irq
> resource\n");
> -
>  	ret = mtk_dp_dt_parse(mtk_dp, pdev);
>  	if (ret)
>  		return dev_err_probe(dev, ret, "Failed to parse dt\n");
>  
> +	/*
> +	 * Request the interrupt and install service routine only if we
> are
> +	 * on full DisplayPort.
> +	 * For eDP, polling the HPD instead is more convenient because
> we
> +	 * don't expect any (un)plug events during runtime, hence we
> can
> +	 * avoid some locking.
> +	 */
> +	if (mtk_dp->data->bridge_type != DRM_MODE_CONNECTOR_eDP) {
> +		mtk_dp->irq = platform_get_irq(pdev, 0);
> +		if (mtk_dp->irq < 0)
> +			return dev_err_probe(dev, mtk_dp->irq,
> +					     "failed to request dp irq
> resource\n");
> +
> +		spin_lock_init(&mtk_dp->irq_thread_lock);
> +
> +		irq_set_status_flags(mtk_dp->irq, IRQ_NOAUTOEN);
> +		ret = devm_request_threaded_irq(dev, mtk_dp->irq,
> mtk_dp_hpd_event,
> +						mtk_dp_hpd_event_thread
> ,
> +						IRQ_TYPE_LEVEL_HIGH,
> dev_name(dev),
> +						mtk_dp);
> +		if (ret)
> +			return dev_err_probe(dev, ret,
> +					     "failed to request
> mediatek dptx irq\n");
> +
> +		mtk_dp->need_debounce = true;
> +		timer_setup(&mtk_dp->debounce_timer,
> mtk_dp_debounce_timer, 0);
> +	}
> +
>  	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);
> -
> -	irq_set_status_flags(mtk_dp->irq, IRQ_NOAUTOEN);
> -	ret = devm_request_threaded_irq(dev, mtk_dp->irq,
> mtk_dp_hpd_event,
> -					mtk_dp_hpd_event_thread,
> -					IRQ_TYPE_LEVEL_HIGH,
> dev_name(dev),
> -					mtk_dp);
> -	if (ret)
> -		return dev_err_probe(dev, ret,
> -				     "failed to request mediatek dptx
> irq\n");
> -
>  	platform_set_drvdata(pdev, mtk_dp);
>  
>  	if (mtk_dp->data->audio_supported) {
> @@ -2626,9 +2642,6 @@ static int mtk_dp_probe(struct platform_device
> *pdev)
>  	mtk_dp->bridge.of_node = dev->of_node;
>  	mtk_dp->bridge.type = mtk_dp->data->bridge_type;
>  
> -	mtk_dp->need_debounce = true;
> -	timer_setup(&mtk_dp->debounce_timer, mtk_dp_debounce_timer, 0);
> -
>  	if (mtk_dp->bridge.type == DRM_MODE_CONNECTOR_eDP) {
>  		/*
>  		 * Set the data lanes to idle in case the bootloader
> didn't
> @@ -2639,6 +2652,9 @@ static int mtk_dp_probe(struct platform_device
> *pdev)
>  		mtk_dp_initialize_aux_settings(mtk_dp);
>  		mtk_dp_power_enable(mtk_dp);
>  
> +		/* Disable HW interrupts: we don't need any for eDP */
> +		mtk_dp_hwirq_enable(mtk_dp, false);
> +
>  		/*
>  		 * Power on the AUX to allow reading the EDID from aux-
> bus:
>  		 * please note that it is necessary to call power off
> in the
> @@ -2684,7 +2700,8 @@ static int mtk_dp_remove(struct platform_device
> *pdev)
>  
>  	pm_runtime_put(&pdev->dev);
>  	pm_runtime_disable(&pdev->dev);
> -	del_timer_sync(&mtk_dp->debounce_timer);
> +	if (mtk_dp->data->bridge_type != DRM_MODE_CONNECTOR_eDP)
> +		del_timer_sync(&mtk_dp->debounce_timer);
>  	platform_device_unregister(mtk_dp->phy_dev);
>  	if (mtk_dp->audio_pdev)
>  		platform_device_unregister(mtk_dp->audio_pdev);
> @@ -2698,7 +2715,8 @@ static int mtk_dp_suspend(struct device *dev)
>  	struct mtk_dp *mtk_dp = dev_get_drvdata(dev);
>  
>  	mtk_dp_power_disable(mtk_dp);
> -	mtk_dp_hwirq_enable(mtk_dp, false);
> +	if (mtk_dp->bridge.type != DRM_MODE_CONNECTOR_eDP)
> +		mtk_dp_hwirq_enable(mtk_dp, false);
>  	pm_runtime_put_sync(dev);
>  
>  	return 0;
> @@ -2710,7 +2728,8 @@ static int mtk_dp_resume(struct device *dev)
>  
>  	pm_runtime_get_sync(dev);
>  	mtk_dp_init_port(mtk_dp);
> -	mtk_dp_hwirq_enable(mtk_dp, true);
> +	if (mtk_dp->bridge.type != DRM_MODE_CONNECTOR_eDP)
> +		mtk_dp_hwirq_enable(mtk_dp, true);
>  	mtk_dp_power_enable(mtk_dp);
>  
>  	return 0;