From: Maxime Ripard <mripard@kernel.org>
To: Sam Ravnborg <sam@ravnborg.org>
Cc: dri-devel@lists.freedesktop.org,
Thierry Reding <thierry.reding@gmail.com>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Abhinav Kumar <abhinavk@codeaurora.org>,
Andrzej Hajda <a.hajda@samsung.com>,
Benjamin Gaignard <benjamin.gaignard@linaro.org>,
Boris Brezillon <boris.brezillon@collabora.com>,
Daniel Vetter <daniel@ffwll.ch>, David Airlie <airlied@linux.ie>,
Jagan Teki <jagan@amarulasolutions.com>,
Jitao Shi <jitao.shi@mediatek.com>,
Linus Walleij <linus.walleij@linaro.org>,
linux-arm-kernel@lists.infradead.org,
linux-mediatek@lists.infradead.org,
linux-renesas-soc@vger.kernel.org,
linux-rockchip@lists.infradead.org,
linux-samsung-soc@vger.kernel.org, linux-tegra@vger.kernel.org,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Neil Armstrong <narmstrong@baylibre.com>,
NXP Linux Team <linux-imx@nxp.com>,
Pengutronix Kernel Team <kernel@pengutronix.de>,
Purism Kernel Team <kernel@puri.sm>, Sean Paul <sean@poorly.run>,
Stefan Agner <stefan@agner.ch>,
Tomi Valkeinen <tomi.valkeinen@ti.com>
Subject: Re: [PATCH v1 07/26] drm/panel: remove get_timings
Date: Wed, 4 Dec 2019 09:05:39 +0100 [thread overview]
Message-ID: <20191204080539.z2ovccj4kjsrpttm@gilmour.lan> (raw)
In-Reply-To: <20191203083935.GB30687@ravnborg.org>
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On Tue, Dec 03, 2019 at 09:39:36AM +0100, Sam Ravnborg wrote:
> On Tue, Dec 03, 2019 at 08:46:59AM +0100, Maxime Ripard wrote:
> > Hi,
> >
> > On Mon, Dec 02, 2019 at 08:32:11PM +0100, Sam Ravnborg wrote:
> > > There was no users - so remove it.
> > > The callback was implemented in two drivers - deleted.
> > >
> > > Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
> > > Cc: Thierry Reding <thierry.reding@gmail.com>
> > > Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
> > > Cc: Sam Ravnborg <sam@ravnborg.org>
> > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > > Cc: Maxime Ripard <mripard@kernel.org>
> > > Cc: David Airlie <airlied@linux.ie>
> > > Cc: Daniel Vetter <daniel@ffwll.ch>
> > > ---
> > > drivers/gpu/drm/panel/panel-seiko-43wvf1g.c | 18 ------------------
> > > drivers/gpu/drm/panel/panel-simple.c | 18 ------------------
> > > include/drm/drm_panel.h | 9 ---------
> > > 3 files changed, 45 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/panel/panel-seiko-43wvf1g.c b/drivers/gpu/drm/panel/panel-seiko-43wvf1g.c
> > > index b878930b17e4..3bcba64235c4 100644
> > > --- a/drivers/gpu/drm/panel/panel-seiko-43wvf1g.c
> > > +++ b/drivers/gpu/drm/panel/panel-seiko-43wvf1g.c
> > > @@ -217,30 +217,12 @@ static int seiko_panel_get_modes(struct drm_panel *panel,
> > > return seiko_panel_get_fixed_modes(p, connector);
> > > }
> > >
> > > -static int seiko_panel_get_timings(struct drm_panel *panel,
> > > - unsigned int num_timings,
> > > - struct display_timing *timings)
> > > -{
> > > - struct seiko_panel *p = to_seiko_panel(panel);
> > > - unsigned int i;
> > > -
> > > - if (p->desc->num_timings < num_timings)
> > > - num_timings = p->desc->num_timings;
> > > -
> > > - if (timings)
> > > - for (i = 0; i < num_timings; i++)
> > > - timings[i] = p->desc->timings[i];
> > > -
> > > - return p->desc->num_timings;
> > > -}
> > > -
> > > static const struct drm_panel_funcs seiko_panel_funcs = {
> > > .disable = seiko_panel_disable,
> > > .unprepare = seiko_panel_unprepare,
> > > .prepare = seiko_panel_prepare,
> > > .enable = seiko_panel_enable,
> > > .get_modes = seiko_panel_get_modes,
> > > - .get_timings = seiko_panel_get_timings,
> > > };
> >
> > If anything, I think we should grow the usage of timings and / or make
> > it usable by everyone.
> >
> > 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.
> >
> > Timings solves the first case since we have the operating range now
> > and not a single set of timings, and it solves the second since we can
> > use that range to take those measures instead of taking a shot in the
> > dark.
> >
> > I appreciate that it's pretty far from where we are today, but
> > removing the get_timings means that all the timings already defined in
> > the panel drivers are becoming useless too, and that eventually it
> > will get removed.
>
> Thanks for this nice explanation. I will drop the patch,
> and add an entry to my TODO list to look closer at this later.
> There are things to improve in this area.
>
> So the conclusion is more work rather than removing code :-)
Yeah, unfortunately.. :)
Maxime
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next prev parent reply other threads:[~2019-12-04 8:05 UTC|newest]
Thread overview: 55+ 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 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 [this message]
2019-12-03 15:20 ` Linus Walleij
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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