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From: Linus Walleij <linus.walleij@linaro.org>
To: Maxime Ripard <mripard@kernel.org>
Cc: Neil Armstrong <narmstrong@baylibre.com>,
	David Airlie <airlied@linux.ie>,
	"open list:DRM PANEL DRIVERS" <dri-devel@lists.freedesktop.org>,
	Andrzej Hajda <a.hajda@samsung.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Benjamin Gaignard <benjamin.gaignard@linaro.org>,
	Sam Ravnborg <sam@ravnborg.org>,
	linux-samsung-soc <linux-samsung-soc@vger.kernel.org>,
	"open list:ARM/Rockchip SoC..."
	<linux-rockchip@lists.infradead.org>,
	Tomi Valkeinen <tomi.valkeinen@ti.com>,
	NXP Linux Team <linux-imx@nxp.com>,
	Jagan Teki <jagan@amarulasolutions.com>,
	Jitao Shi <jitao.shi@mediatek.com>,
	Pengutronix Kernel Team <kernel@pengutronix.de>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Abhinav Kumar <abhinavk@codeaurora.org>,
	"moderated list:ARM/Mediatek SoC support"
	<linux-mediatek@lists.infradead.org>,
	Stefan Agner <stefan@agner.ch>,
	linux-tegra@vger.kernel.org, Sean Paul <sean@poorly.run>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Purism Kernel Team <kernel@puri.sm>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	Boris Brezillon <boris.brezillon@collabora.com>,
	Daniel Vetter <daniel@ffwll.ch>
Subject: Re: [PATCH v1 07/26] drm/panel: remove get_timings
Date: Tue, 3 Dec 2019 16:20:24 +0100	[thread overview]
Message-ID: <CACRpkdZrReQs08+bXS7s7eJ-K76nMGvRgQ-L-1-baunEtiF40g@mail.gmail.com> (raw)
In-Reply-To: <20191203074659.ilsyv4yx7pzw5vax@gilmour.lan>

Hi Maxime,

On Tue, Dec 3, 2019 at 8:47 AM Maxime Ripard <mripard@kernel.org> wrote:

> Using only the mode as we do currently has a bunch of shortcomings as
> almost no encoder will be able to provide the typical pixel clock, and
> that situation leads to multiple things:
>
>   - If someone working on one encoder wants to upstream a panel they
>     have tested, chances are this will not be the typical pixel clock
>     / timings being used but rather the one that will match what that
>     SoC is capable of. Trouble comes when a second user comes in with
>     a different encoder and different capabilities, and then we have a
>     maintainance fight over which timing is the true timing (with a
>     significant chance that none of them are).
>
>   - If we can't match the pixel clock, we currently have no easy way
>     to make the usual measures of reducing / growing the porches and
>     blankings areas to match the pixel clock we can provide, since we
>     don't have an easy way to get the tolerance on those timings for a
>     given panel. There's some ad hoc solutions on some drivers (I
>     think vc4 has that?) to ignore the panel and just play around with
>     the timings, but I think this should be generalised.

I've been confused with these things as they look today and it seems
the whole struct drm_display_mode could need some improvement?

If .clock is supposed to be htotal * vtotal * vrefresh, what is the
.clock doing there anyway.

Sadly I am too inexperienced to realize where the tolerances should
be stated, but I guess just stating that hsync_start etc are typical,
then specify some tolerance for each would help a bit?

On the DSI displays in video mode there is also this EOL area
which seems to be where the logic is normally just idling for a
while, that can be adjusted on some hardware as well, but
I don't quite understand it admittedly. Sometimes I wonder if
anyone really understands DSI... :/

Yours,
Linus Walleij

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  parent reply	other threads:[~2019-12-03 15:20 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-02 19:32 [PATCH v1 0/26] drm/panel infrastructure + backlight update Sam Ravnborg
2019-12-02 19:32 ` [PATCH v1 01/26] drm/drm_panel: no error when no callback Sam Ravnborg
2019-12-03  6:24   ` Laurent Pinchart
2019-12-02 19:32 ` [PATCH v1 02/26] drm/panel: add backlight support Sam Ravnborg
2019-12-03  6:32   ` Laurent Pinchart
2019-12-02 19:32 ` [PATCH v1 03/26] drm/panel: simple: use drm_panel " Sam Ravnborg
2019-12-03  6:39   ` Laurent Pinchart
2019-12-02 19:32 ` [PATCH v1 04/26] drm: get drm_bridge_panel connector via helper Sam Ravnborg
2019-12-03  6:44   ` Laurent Pinchart
2019-12-03 13:22   ` Linus Walleij
2019-12-02 19:32 ` [PATCH v1 05/26] drm/panel: add drm_connector argument to get_modes() Sam Ravnborg
2019-12-03  6:50   ` Laurent Pinchart
2019-12-03 13:25   ` Linus Walleij
2019-12-04 12:08   ` Guido Günther
2019-12-04 13:11     ` Laurent Pinchart
2019-12-02 19:32 ` [PATCH v1 06/26] drm/panel: decouple connector from drm_panel Sam Ravnborg
2019-12-03  6:54   ` Laurent Pinchart
2019-12-03 13:26   ` Linus Walleij
2019-12-02 19:32 ` [PATCH v1 07/26] drm/panel: remove get_timings Sam Ravnborg
2019-12-03  7:02   ` Laurent Pinchart
2019-12-03  7:46   ` Maxime Ripard
2019-12-03  8:18     ` Laurent Pinchart
2019-12-03  8:39     ` Sam Ravnborg
2019-12-04  8:05       ` Maxime Ripard
2019-12-03 15:20     ` Linus Walleij [this message]
2019-12-04  8:16       ` Maxime Ripard
2019-12-04  8:23         ` Laurent Pinchart
2019-12-10 21:33         ` Linus Walleij
2019-12-02 19:32 ` [PATCH v1 08/26] drm/panel: drop drm_device from drm_panel Sam Ravnborg
2019-12-03  7:15   ` Laurent Pinchart
2019-12-03 13:27   ` Linus Walleij
2019-12-02 19:32 ` [PATCH v1 09/26] drm/panel: feiyang-fy07024di26a30d: use drm_panel backlight support Sam Ravnborg
2019-12-02 19:32 ` [PATCH v1 10/26] drm/panel: ilitek-ili9881c: " Sam Ravnborg
2019-12-02 19:32 ` [PATCH v1 11/26] drm/panel: innolux-p079zca: " Sam Ravnborg
2019-12-02 19:32 ` [PATCH v1 12/26] drm/panel: kingdisplay-kd097d04: " Sam Ravnborg
2019-12-02 19:32 ` [PATCH v1 13/26] drm/panel: lvds: " Sam Ravnborg
2019-12-03  7:16   ` Laurent Pinchart
2019-12-02 19:32 ` [PATCH v1 14/26] drm/panel: olimex-lcd-olinuxino: " Sam Ravnborg
2019-12-02 19:32 ` [PATCH v1 15/26] drm/panel: osd-osd101t2587-53ts: " Sam Ravnborg
2019-12-02 19:32 ` [PATCH v1 16/26] drm/panel: panasonic-vvx10f034n00: " Sam Ravnborg
2019-12-02 19:32 ` [PATCH v1 17/26] drm/panel: raydium-rm68200: " Sam Ravnborg
2019-12-02 19:32 ` [PATCH v1 18/26] drm/panel: rocktech-jh057n00900: " Sam Ravnborg
2019-12-04 12:04   ` Guido Günther
2019-12-02 19:32 ` [PATCH v1 19/26] drm/panel: ronbo-rb070d30: " Sam Ravnborg
2019-12-02 19:32 ` [PATCH v1 20/26] drm/panel: seiko-43wvf1g: " Sam Ravnborg
2019-12-02 19:32 ` [PATCH v1 21/26] drm/panel: sharp-lq101r1sx01: " Sam Ravnborg
2019-12-02 19:32 ` [PATCH v1 22/26] drm/panel: sharp-ls043t1le01: " Sam Ravnborg
2019-12-02 19:32 ` [PATCH v1 23/26] drm/panel: sitronix-st7701: " Sam Ravnborg
2019-12-02 19:32 ` [PATCH v1 24/26] drm/panel: sitronix-st7789v: " Sam Ravnborg
2019-12-02 19:32 ` [PATCH v1 25/26] drm/panel: tpo-td028ttec1: " Sam Ravnborg
2019-12-03  7:16   ` Laurent Pinchart
2019-12-02 19:32 ` [PATCH v1 26/26] drm/panel: tpo-tpg110: " Sam Ravnborg
2019-12-03 13:20   ` Linus Walleij
2019-12-02 19:59 ` [PATCH v1 0/26] drm/panel infrastructure + backlight update Jeffrey Hugo
2019-12-02 20:48   ` Sam Ravnborg
2019-12-02 20:51     ` Jeffrey Hugo
2019-12-03  7:24 ` Laurent Pinchart
2019-12-03  8:33   ` Sam Ravnborg

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