linux-kernel - Re: [PATCH v6 11/11] drm/mediatek: dp: Don't register HPD interrupt handler for eDP case

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Message-ID: <eaeeb44b-b102-1865-9600-58de7f682ee8@collabora.com>
Date:   Tue, 25 Jul 2023 09:19:59 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     CK Hu (胡俊光) <ck.hu@...iatek.com>,
        "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "wenst@...omium.org" <wenst@...omium.org>,
        "kernel@...labora.com" <kernel@...labora.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "nfraprado@...labora.com" <nfraprado@...labora.com>
Subject: Re: [PATCH v6 11/11] drm/mediatek: dp: Don't register HPD interrupt
 handler for eDP case

Il 25/07/23 08:37, CK Hu (胡俊光) ha scritto:
> 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.
>>   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.
>>
>> Signed-off-by: AngeloGioacchino Del Regno <
>> angelogioacchino.delregno@...labora.com>
>> ---
>>   drivers/gpu/drm/mediatek/mtk_dp.c | 81 ++++++++++++++++++-----------
>> --
>>   1 file changed, 46 insertions(+), 35 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c
>> b/drivers/gpu/drm/mediatek/mtk_dp.c
>> index e74295ba9707..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);
>> @@ -2579,40 +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");
>> -
>> -	mtk_dp->next_bridge = devm_drm_of_get_bridge(dev, dev->of_node,
>> 1, 0);
>> -	if (IS_ERR(mtk_dp->next_bridge) &&
>> -	    PTR_ERR(mtk_dp->next_bridge) == -ENODEV)
>> -		mtk_dp->next_bridge = NULL;
>> -	else if (IS_ERR(mtk_dp->next_bridge))
>> -		return dev_err_probe(dev, PTR_ERR(mtk_dp->next_bridge),
>> -				     "Failed to get bridge\n");
>> -
> 
> Why remove next_bridge setting?
> 

Hello CK,

Thanks for making me notice that! The removal of this code snippet belongs
to patch [9/11] `drm/mediatek: dp: Add support for embedded DisplayPort aux-bus`
because in that patch I am moving the call to devm_drm_of_get_bridge() to function
mtk_dp_edp_link_panel(), which is called as a .done_probing() callback if the eDP
panel is on aux-bus, or "manually" if not on aux-bus.

I'll send a v7 with the removal of this snippet in the right patch.

Thanks again,
Angelo