From: Nikolaus Voss <nv@vosn.de>
To: Marek Vasut <marex@denx.de>
Cc: Alexander Stein <alexander.stein@ew.tq-group.com>,
Liu Ying <victor.liu@nxp.com>,
Luca Ceresoli <luca.ceresoli@bootlin.com>,
Fabio Estevam <festevam@denx.de>,
Andrzej Hajda <andrzej.hajda@intel.com>,
Neil Armstrong <neil.armstrong@linaro.org>,
Robert Foss <rfoss@kernel.org>,
Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
Jonas Karlman <jonas@kwiboo.se>,
Jernej Skrabec <jernej.skrabec@gmail.com>,
David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
miquel.raynal@bootlin.com, nikolaus.voss@haag-streit.com,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] drm: bridge: fsl-ldb: fixup mode on freq mismatch
Date: Wed, 04 Dec 2024 11:40:37 +0100 [thread overview]
Message-ID: <abcc89936f44fd884b9c5da65ea64c42@vosn.de> (raw)
In-Reply-To: <2d7f8afc-119a-4080-93be-bf3daf017e5e@denx.de>
Hi Marek,
On 03.12.2024 21:15, Marek Vasut wrote:
> On 12/3/24 8:09 PM, Nikolaus Voss wrote:
>> LDB clock has to be a fixed multiple of the pixel clock.
>> As LDB and pixel clock are derived from different clock sources
>
> Can you please share the content of /sys/kernel/debug/clk/clk_summary ?
Sure. Without my patch:
video_pll1_ref_sel 1 1 0 24000000
0 0 50000 Y deviceless
no_connection_id
video_pll1 1 1 0
1039500000 0 0 50000 Y deviceless
no_connection_id
video_pll1_bypass 1 1 0
1039500000 0 0 50000 Y deviceless
no_connection_id
video_pll1_out 2 2 0
1039500000 0 0 50000 Y deviceless
no_connection_id
media_ldb 1 1 0 346500000
0 0 50000 Y
32ec0000.blk-ctrl:bridge@5c ldb
deviceless
no_connection_id
media_ldb_root_clk 0 0 0
346500000 0 0 50000 Y deviceless
no_connection_id
media_disp2_pix 1 1 0 51975000
0 0 50000 Y deviceless
no_connection_id
media_disp2_pix_root_clk 1 1 0
51975000 0 0 50000 Y
32e90000.display-controller pix
Here 346500000 (media_ldb) != 7 * 51975000 (media_disp2_pix)
-> distorted panel image (if any).
The requested panel pixel clock from EDID is 51200000.
This is the same with my patch:
video_pll1_ref_sel 1 1 0 24000000
0 0 50000 Y deviceless
no_connection_id
video_pll1 1 1 0
1039500000 0 0 50000 Y deviceless
no_connection_id
video_pll1_bypass 1 1 0
1039500000 0 0 50000 Y deviceless
no_connection_id
video_pll1_out 2 2 0
1039500000 0 0 50000 Y deviceless
no_connection_id
media_ldb 1 1 0 346500000
0 0 50000 Y
32ec0000.blk-ctrl:bridge@5c ldb
deviceless
no_connection_id
media_ldb_root_clk 0 0 0
346500000 0 0 50000 Y deviceless
no_connection_id
media_disp2_pix 1 1 0 49500000
0 0 50000 Y deviceless
no_connection_id
media_disp2_pix_root_clk 1 1 0
49500000 0 0 50000 Y
32e90000.display-controller pix
So, here 346500000 (media_ldb) = 7 * 49500000 (media_disp2_pix).
-> stable panel image, but pixel clock reduced to 49.5 MHz from
requested 51.2 MHz.
My conclusion: The clock source is the same, nevertheless the
ldb/pixel clock constraint cannot be satisfied without either
modifying the pll clock or the pixel clock.
--
Nikolaus Voss
next prev parent reply other threads:[~2024-12-04 10:40 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-03 19:09 Nikolaus Voss
2024-12-03 20:15 ` Marek Vasut
2024-12-04 10:40 ` Nikolaus Voss [this message]
2024-12-07 11:46 ` Marek Vasut
2024-12-09 9:27 ` Nikolaus Voss
2024-12-09 21:51 ` Marek Vasut
2024-12-11 16:47 ` Nikolaus Voss
2024-12-04 12:48 ` kernel test robot
2024-12-04 22:03 ` kernel test robot
2024-12-06 14:08 ` Miquel Raynal
2024-12-07 6:30 ` Nikolaus Voss
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=abcc89936f44fd884b9c5da65ea64c42@vosn.de \
--to=nv@vosn.de \
--cc=Laurent.pinchart@ideasonboard.com \
--cc=airlied@gmail.com \
--cc=alexander.stein@ew.tq-group.com \
--cc=andrzej.hajda@intel.com \
--cc=daniel@ffwll.ch \
--cc=dri-devel@lists.freedesktop.org \
--cc=festevam@denx.de \
--cc=jernej.skrabec@gmail.com \
--cc=jonas@kwiboo.se \
--cc=linux-kernel@vger.kernel.org \
--cc=luca.ceresoli@bootlin.com \
--cc=marex@denx.de \
--cc=miquel.raynal@bootlin.com \
--cc=neil.armstrong@linaro.org \
--cc=nikolaus.voss@haag-streit.com \
--cc=rfoss@kernel.org \
--cc=victor.liu@nxp.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®