Re: [PATCH v16 3/8] drm/mediatek: Add MT8195 Embedded DisplayPort driver

[CK Hu <ck.hu@mediatek.com>]

Hi, Bo-Chen:

On Fri, 2022-08-05 at 18:14 +0800, Bo-Chen Chen wrote:
> From: Markus Schneider-Pargmann <msp@baylibre.com>
> 
> This patch adds a embedded displayport driver for the MediaTek mt8195
> SoC.
> 
> It supports the MT8195, the embedded DisplayPort units. It offers
> DisplayPort 1.4 with up to 4 lanes.
> 
> The driver creates a child device for the phy. The child device will
> never exist without the parent being active. As they are sharing a
> register range, the parent passes a regmap pointer to the child so
> that
> both can work with the same register range. The phy driver sets
> device
> data that is read by the parent to get the phy device that can be
> used
> to control the phy properties.
> 
> This driver is based on an initial version by
> Jitao shi <jitao.shi@mediatek.com>
> 
> Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> Signed-off-by: Guillaume Ranquet <granquet@baylibre.com>
> Signed-off-by: Bo-Chen Chen <rex-bc.chen@mediatek.com>
> Tested-by: AngeloGioacchino Del Regno <
> angelogioacchino.delregno@collabora.com>
> Reviewed-by: AngeloGioacchino Del Regno <
> angelogioacchino.delregno@collabora.com>
> ---

[snip]

> +
> +static irqreturn_t mtk_dp_hpd_event(int hpd, void *dev)
> +{
> +	struct mtk_dp *mtk_dp = dev;
> +	struct mtk_dp_train_info *train_info = &mtk_dp->train_info;
> +	u32 irq_status;
> +
> +	irq_status = mtk_dp_read(mtk_dp, MTK_DP_TOP_IRQ_STATUS);
> +
> +	if (!(irq_status & RGS_IRQ_STATUS_TRANSMITTER))
> +		return IRQ_HANDLED;

If one of MTK_DP_HPD_INTERRUPT, MTK_DP_HPD_CONNECT,
MTK_DP_HPD_DISCONNECT exist, does it imply RGS_IRQ_STATUS_TRANSMITTER
exist? If so, I think this checking is redundant because we could
directly check MTK_DP_HPD_INTERRUPT, MTK_DP_HPD_CONNECT,
MTK_DP_HPD_DISCONNECT.

> +
> +	irq_status = mtk_dp_swirq_get_clear(mtk_dp) |
> +		     mtk_dp_hwirq_get_clear(mtk_dp);
> +
> +	if (!irq_status)
> +		return IRQ_HANDLED;
> +
> +	if (irq_status & MTK_DP_HPD_INTERRUPT)
> +		train_info->hpd_inerrupt = true;

train_info->hpd_inerrupt is useless, so drop it.

> +
> +	if (!(irq_status & MTK_DP_HPD_CONNECT ||
> +	      irq_status & MTK_DP_HPD_DISCONNECT))
> +		return IRQ_WAKE_THREAD;

this could be changed to

if (irq_status == MTK_DP_HPD_INTERRUPT)
	return IRQ_WAKE_THREAD;

But I find one problem. If irq_status == MTK_DP_HPD_INTERRUPT |
MTK_DP_HPD_CONNECT, the thread would not be waked up. Is this what you
want?

Regards,
CK

> +
> +	if (!!(mtk_dp_read(mtk_dp, MTK_DP_TRANS_P0_3414) &
> +	       HPD_DB_DP_TRANS_P0_MASK))
> +		train_info->cable_plugged_in = true;
> +	else
> +		train_info->cable_plugged_in = false;
> +
> +	mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
> +			   DP_PWR_STATE_BANDGAP_TPLL_LANE,
> +			   DP_PWR_STATE_MASK);
> +
> +	return IRQ_HANDLED;
> +}
> +