Re: [PATCH] drm/dsi: Add _NO_ to MIPI_DSI_* flags disabling features

From: Linus Walleij <linus.walleij@linaro.org>
To: Nicolas Boichat <drinkcat@chromium.org>
Cc: Andrzej Hajda <a.hajda@samsung.com>,
	Robert Foss <robert.foss@linaro.org>,
	Chun-Kuang Hu <chunkuang.hu@kernel.org>,
	Daniel Vetter <daniel@ffwll.ch>, David Airlie <airlied@linux.ie>,
	Emil Velikov <emil.velikov@collabora.com>,
	Inki Dae <inki.dae@samsung.com>,
	Jernej Skrabec <jernej.skrabec@siol.net>,
	Jonas Karlman <jonas@kwiboo.se>,
	Joonyoung Shim <jy0922.shim@samsung.com>,
	Jordan Crouse <jcrouse@codeaurora.org>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	Kyungmin Park <kyungmin.park@samsung.com>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	Maxime Ripard <mripard@kernel.org>,
	Neil Armstrong <narmstrong@baylibre.com>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Rajendra Nayak <rnayak@codeaurora.org>,
	Rikard Falkeborn <rikard.falkeborn@gmail.com>,
	Rob Clark <robdclark@gmail.com>, Sam Ravnborg <sam@ravnborg.org>,
	Sean Paul <sean@poorly.run>,
	Seung-Woo Kim <sw0312.kim@samsung.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Xin Ji <xji@analogixsemi.com>,
	"open list:DRM PANEL DRIVERS" <dri-devel@lists.freedesktop.org>,
	freedreno <freedreno@lists.freedesktop.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	MSM <linux-arm-msm@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"moderated list:ARM/Mediatek SoC support" 
	<linux-mediatek@lists.infradead.org>,
	linux-samsung-soc <linux-samsung-soc@vger.kernel.org>
Subject: Re: [PATCH] drm/dsi: Add _NO_ to MIPI_DSI_* flags disabling features
Date: Mon, 1 Mar 2021 09:59:35 +0100	[thread overview]
Message-ID: <CACRpkdbQa3BZwgtp3=061cu+y+4qkMqtXQhXH_VuHB3KcLyDCA@mail.gmail.com> (raw)
In-Reply-To: <20210211113309.1.I629b2366a6591410359c7fcf6d385b474b705ca2@changeid>

On Thu, Feb 11, 2021 at 4:34 AM Nicolas Boichat <drinkcat@chromium.org> wrote:

> Many of the DSI flags have names opposite to their actual effects,
> e.g. MIPI_DSI_MODE_EOT_PACKET means that EoT packets will actually
> be disabled. Fix this by including _NO_ in the flag names, e.g.
> MIPI_DSI_MODE_NO_EOT_PACKET.

Unless someone like me interpreted it literally...

Like in these:

>  drivers/gpu/drm/mcde/mcde_dsi.c                      | 2 +-
>  drivers/gpu/drm/panel/panel-novatek-nt35510.c        | 2 +-
>  drivers/gpu/drm/panel/panel-samsung-s6d16d0.c        | 2 +-
>  drivers/gpu/drm/panel/panel-sony-acx424akp.c         | 2 +-

> diff --git a/drivers/gpu/drm/mcde/mcde_dsi.c b/drivers/gpu/drm/mcde/mcde_dsi.c
> index 2314c8122992..f4cdc3cfd7d0 100644
> --- a/drivers/gpu/drm/mcde/mcde_dsi.c
> +++ b/drivers/gpu/drm/mcde/mcde_dsi.c
> @@ -760,7 +760,7 @@ static void mcde_dsi_start(struct mcde_dsi *d)
>                 DSI_MCTL_MAIN_DATA_CTL_BTA_EN |
>                 DSI_MCTL_MAIN_DATA_CTL_READ_EN |
>                 DSI_MCTL_MAIN_DATA_CTL_REG_TE_EN;
> -       if (d->mdsi->mode_flags & MIPI_DSI_MODE_EOT_PACKET)
> +       if (d->mdsi->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET)
>                 val |= DSI_MCTL_MAIN_DATA_CTL_HOST_EOT_GEN;

If you read the code you can see that this is interpreted as inserting
an EOT packet, so here you need to change the logic such:

if (!d->mdsi->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET)
    val |= DSI_MCTL_MAIN_DATA_CTL_HOST_EOT_GEN;

This will make sure the host generates the EOT packet in HS mode
*unless* the flag is set.

(I checked the data sheet.)

> diff --git a/drivers/gpu/drm/panel/panel-novatek-nt35510.c b/drivers/gpu/drm/panel/panel-novatek-nt35510.c
> index b9a0e56f33e2..9d9334656803 100644
> --- a/drivers/gpu/drm/panel/panel-novatek-nt35510.c
> +++ b/drivers/gpu/drm/panel/panel-novatek-nt35510.c
> @@ -899,7 +899,7 @@ static int nt35510_probe(struct mipi_dsi_device *dsi)
>         dsi->hs_rate = 349440000;
>         dsi->lp_rate = 9600000;
>         dsi->mode_flags = MIPI_DSI_CLOCK_NON_CONTINUOUS |
> -               MIPI_DSI_MODE_EOT_PACKET;
> +               MIPI_DSI_MODE_NO_EOT_PACKET;

Here you should just delete the MIPI_DSI_MODE_EOT_PACKET
flag because this was used with the MCDE driver which interpret the
flag literally.

> diff --git a/drivers/gpu/drm/panel/panel-samsung-s6d16d0.c b/drivers/gpu/drm/panel/panel-samsung-s6d16d0.c
> index 4aac0d1573dd..b04b9975e9b2 100644
> --- a/drivers/gpu/drm/panel/panel-samsung-s6d16d0.c
> +++ b/drivers/gpu/drm/panel/panel-samsung-s6d16d0.c
> @@ -186,7 +186,7 @@ static int s6d16d0_probe(struct mipi_dsi_device *dsi)
>          */
>         dsi->mode_flags =
>                 MIPI_DSI_CLOCK_NON_CONTINUOUS |
> -               MIPI_DSI_MODE_EOT_PACKET;
> +               MIPI_DSI_MODE_NO_EOT_PACKET;

Same, just delete the flag.

> --- a/drivers/gpu/drm/panel/panel-samsung-s6e63m0-dsi.c
> +++ b/drivers/gpu/drm/panel/panel-samsung-s6e63m0-dsi.c
> @@ -97,7 +97,7 @@ static int s6e63m0_dsi_probe(struct mipi_dsi_device *dsi)
>         dsi->hs_rate = 349440000;
>         dsi->lp_rate = 9600000;
>         dsi->mode_flags = MIPI_DSI_MODE_VIDEO |
> -               MIPI_DSI_MODE_EOT_PACKET |
> +               MIPI_DSI_MODE_NO_EOT_PACKET |
>                 MIPI_DSI_MODE_VIDEO_BURST;

Same, just delete the flag.

> diff --git a/drivers/gpu/drm/panel/panel-sony-acx424akp.c b/drivers/gpu/drm/panel/panel-sony-acx424akp.c
> index 065efae213f5..6b706cbf2f9c 100644
> --- a/drivers/gpu/drm/panel/panel-sony-acx424akp.c
> +++ b/drivers/gpu/drm/panel/panel-sony-acx424akp.c
> @@ -450,7 +450,7 @@ static int acx424akp_probe(struct mipi_dsi_device *dsi)
>         else
>                 dsi->mode_flags =
>                         MIPI_DSI_CLOCK_NON_CONTINUOUS |
> -                       MIPI_DSI_MODE_EOT_PACKET;
> +                       MIPI_DSI_MODE_NO_EOT_PACKET;

Same, just delete the flag.

These are all just semantic bugs due to the ambiguity of the flags, it is
possible to provide a Fixes: flag for each file using this flag the wrong way
but I dunno if it's worth it.

Yours,
Linus Walleij