From: Hector Martin <marcan@marcan.st>
To: Pekka Paalanen <ppaalanen@gmail.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <mripard@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
dri-devel@lists.freedesktop.org,
Alyssa Rosenzweig <alyssa@rosenzweig.io>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] drm/format-helper: Add drm_fb_xrgb8888_to_xrgb2101010_dstclip()
Date: Mon, 22 Nov 2021 19:05:16 +0900 [thread overview]
Message-ID: <7e1356b9-3122-e169-193e-37547a50499a@marcan.st> (raw)
In-Reply-To: <20211122115247.257f30fa@eldfell>
On 22/11/2021 18.52, Pekka Paalanen wrote:
> On Wed, 17 Nov 2021 23:58:28 +0900
> Hector Martin <marcan@marcan.st> wrote:
>
>> Add XRGB8888 emulation support for devices that can only do XRGB2101010.
>>
>> This is chiefly useful for simpledrm on Apple devices where the
>> bootloader-provided framebuffer is 10-bit, which already works fine with
>> simplefb. This is required to make simpledrm support this too.
>>
>> Signed-off-by: Hector Martin <marcan@marcan.st>
>> ---
>> drivers/gpu/drm/drm_format_helper.c | 64 +++++++++++++++++++++++++++++
>> include/drm/drm_format_helper.h | 4 ++
>> 2 files changed, 68 insertions(+)
>
> Hi Hector,
>
> I'm curious, since the bootloader seems to always set up a 10-bit mode,
> is there a reason for it that you can guess? Is the monitor in WCG or
> even HDR mode?
My guess is that Apple prefer to use 10-bit framebuffers for seamless
handover with their graphics stack, which presumably uses 10-bit
framebuffers these days. It seems to be unconditional; I've never seen
anything but 10 bits across all Apple devices, both with the internal
panels on laptops and with bog standard external displays on the Mac
Mini via HDMI. HDR is not necessary, even very dumb capture cards and
old screens get a 10-bit framebufer in memory.
The only time I see an 8-bit framebuffer is with *no* monitor connected
on the Mini, in which case you get an 8-bit 640x1136 dummy framebuffer
(that's the iPhone 5 screen resolution... :-) )
--
Hector Martin (marcan@marcan.st)
Public Key: https://mrcn.st/pub
WARNING: multiple messages have this Message-ID (diff)
From: Hector Martin <marcan@marcan.st>
To: Pekka Paalanen <ppaalanen@gmail.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>,
David Airlie <airlied@linux.ie>,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
Alyssa Rosenzweig <alyssa@rosenzweig.io>
Subject: Re: [PATCH 2/3] drm/format-helper: Add drm_fb_xrgb8888_to_xrgb2101010_dstclip()
Date: Mon, 22 Nov 2021 19:05:16 +0900 [thread overview]
Message-ID: <7e1356b9-3122-e169-193e-37547a50499a@marcan.st> (raw)
In-Reply-To: <20211122115247.257f30fa@eldfell>
On 22/11/2021 18.52, Pekka Paalanen wrote:
> On Wed, 17 Nov 2021 23:58:28 +0900
> Hector Martin <marcan@marcan.st> wrote:
>
>> Add XRGB8888 emulation support for devices that can only do XRGB2101010.
>>
>> This is chiefly useful for simpledrm on Apple devices where the
>> bootloader-provided framebuffer is 10-bit, which already works fine with
>> simplefb. This is required to make simpledrm support this too.
>>
>> Signed-off-by: Hector Martin <marcan@marcan.st>
>> ---
>> drivers/gpu/drm/drm_format_helper.c | 64 +++++++++++++++++++++++++++++
>> include/drm/drm_format_helper.h | 4 ++
>> 2 files changed, 68 insertions(+)
>
> Hi Hector,
>
> I'm curious, since the bootloader seems to always set up a 10-bit mode,
> is there a reason for it that you can guess? Is the monitor in WCG or
> even HDR mode?
My guess is that Apple prefer to use 10-bit framebuffers for seamless
handover with their graphics stack, which presumably uses 10-bit
framebuffers these days. It seems to be unconditional; I've never seen
anything but 10 bits across all Apple devices, both with the internal
panels on laptops and with bog standard external displays on the Mac
Mini via HDMI. HDR is not necessary, even very dumb capture cards and
old screens get a 10-bit framebufer in memory.
The only time I see an 8-bit framebuffer is with *no* monitor connected
on the Mini, in which case you get an 8-bit 640x1136 dummy framebuffer
(that's the iPhone 5 screen resolution... :-) )
--
Hector Martin (marcan@marcan.st)
Public Key: https://mrcn.st/pub
next prev parent reply other threads:[~2021-11-22 10:05 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-17 14:58 [PATCH 0/3] drm/simpledrm: Apple M1 / DT platform support fixes Hector Martin
2021-11-17 14:58 ` Hector Martin
2021-11-17 14:58 ` [PATCH 1/3] drm/simpledrm: Bind to OF framebuffers in /chosen Hector Martin
2021-11-17 14:58 ` Hector Martin
2021-11-18 9:19 ` Thomas Zimmermann
2021-11-18 9:19 ` Thomas Zimmermann
2021-11-20 3:23 ` Hector Martin
2021-11-20 3:23 ` Hector Martin
2021-11-29 11:26 ` Thomas Zimmermann
2021-11-29 11:26 ` Thomas Zimmermann
2021-11-29 19:29 ` Rob Herring
2021-11-29 19:29 ` Rob Herring
2021-11-30 6:44 ` Javier Martinez Canillas
2021-11-30 6:44 ` Javier Martinez Canillas
2021-11-30 8:31 ` Thomas Zimmermann
2021-11-30 8:31 ` Thomas Zimmermann
2021-11-30 9:31 ` Javier Martinez Canillas
2021-11-30 9:31 ` Javier Martinez Canillas
2021-11-30 18:25 ` Rob Herring
2021-11-30 18:25 ` Rob Herring
2021-11-19 1:21 ` kernel test robot
2021-11-19 1:21 ` kernel test robot
2021-11-17 14:58 ` [PATCH 2/3] drm/format-helper: Add drm_fb_xrgb8888_to_xrgb2101010_dstclip() Hector Martin
2021-11-17 14:58 ` Hector Martin
2021-11-18 9:16 ` Thomas Zimmermann
2021-11-18 9:16 ` Thomas Zimmermann
2021-11-22 9:52 ` Pekka Paalanen
2021-11-22 9:52 ` Pekka Paalanen
2021-11-22 10:05 ` Hector Martin [this message]
2021-11-22 10:05 ` Hector Martin
2021-11-22 10:39 ` Pekka Paalanen
2021-11-22 10:39 ` Pekka Paalanen
2021-11-17 14:58 ` [PATCH 3/3] drm/simpledrm: Enable XRGB2101010 format Hector Martin
2021-11-17 14:58 ` Hector Martin
2021-11-18 9:16 ` Thomas Zimmermann
2021-11-18 9:16 ` Thomas Zimmermann
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