linux-kernel - Re: [PATCH v10 18/21] drm/mediatek: Add mt8195 Embedded DisplayPort driver

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Message-ID: <828da579f872747943dbb7684b35f58bc592c6ca.camel@mediatek.com>
Date:   Mon, 30 May 2022 18:08:33 +0800
From:   CK Hu <ck.hu@...iatek.com>
To:     Guillaume Ranquet <granquet@...libre.com>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "David Airlie" <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        "Kishon Vijay Abraham I" <kishon@...com>,
        Vinod Koul <vkoul@...nel.org>, "Helge Deller" <deller@....de>,
        Jitao shi <jitao.shi@...iatek.com>
CC:     Markus Schneider-Pargmann <msp@...libre.com>,
        <dri-devel@...ts.freedesktop.org>,
        <linux-mediatek@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-phy@...ts.infradead.org>, <linux-fbdev@...r.kernel.org>
Subject: Re: [PATCH v10 18/21] drm/mediatek: Add mt8195 Embedded DisplayPort
 driver

Hi, Guillaume:

On Mon, 2022-05-23 at 12:47 +0200, Guillaume Ranquet wrote:
> From: Markus Schneider-Pargmann <msp@...libre.com>
> 
> This patch adds a 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
> Jason-JH.Lin <jason-jh.lin@...iatek.com>.
> 
> Signed-off-by: Markus Schneider-Pargmann <msp@...libre.com>
> Signed-off-by: Guillaume Ranquet <granquet@...libre.com>
> ---
>  

[snip]

> +
> +static irqreturn_t mtk_dp_hpd_isr_handler(struct mtk_dp *mtk_dp)
> +{
> +	bool connected;
> +	u16 swirq_status = mtk_dp_swirq_get_clear(mtk_dp);
> +	u8 hwirq_status = mtk_dp_hwirq_get_clear(mtk_dp);
> +	struct mtk_dp_train_info *train_info = &mtk_dp->train_info;
> +
> +	train_info->irq_status |= hwirq_status | swirq_status;

You mix software control variable and irq status here. Break each flag
in irq_status to variables in train_info to decouple software control
variable and irq status.

> +
> +	if (!train_info->irq_status)
> +		return IRQ_HANDLED;
> +
> +	connected = mtk_dp_plug_state(mtk_dp);
> +	if (connected || !train_info->cable_plugged_in)
> +		train_info->irq_status &= ~MTK_DP_HPD_DISCONNECT;
> +	else if (!connected || train_info->cable_plugged_in)
> +		train_info->irq_status &= ~MTK_DP_HPD_CONNECT;
> +
> +	if (!(train_info->irq_status &
> +	      (MTK_DP_HPD_CONNECT | MTK_DP_HPD_DISCONNECT)))
> +		return IRQ_HANDLED;
> +
> +	if (train_info->irq_status & MTK_DP_HPD_CONNECT) {
> +		train_info->irq_status &= ~MTK_DP_HPD_CONNECT;
> +		train_info->cable_plugged_in = true;
> +	} else {
> +		train_info->irq_status &= ~MTK_DP_HPD_DISCONNECT;
> +		train_info->cable_plugged_in = false;
> +		mtk_dp->train_state = MTK_DP_TRAIN_STATE_STARTUP;
> +	}
> +	train_info->cable_state_change = true;
> +
> +	return IRQ_WAKE_THREAD;
> +}
> +