drm/tidss: Remove max_pclk_khz and min_pclk_khz from tidss display features

Browse source

[ Upstream commit 527e132573 ]

The TIDSS hardware does not have independent maximum or minimum pixel
clock limits for each video port. Instead, these limits are determined
by the SoC's clock architecture. Previously, this constraint was
modeled using the 'max_pclk_khz' and 'min_pclk_khz' fields in
'dispc_features', but this approach is static and does not account for
the dynamic behavior of PLLs.

This patch removes the 'max_pclk_khz' and 'min_pclk_khz' fields from
'dispc_features'. The correct way to check if a requested mode's pixel
clock is supported is by using 'clk_round_rate()' in the 'mode_valid()'
hook. If the best frequency match for the mode clock falls within the
supported tolerance, it is approved. TIDSS supports a 5% pixel clock
tolerance, which is now reflected in the validation logic.

This change allows existing DSS-compatible drivers to be reused across
SoCs that only differ in their pixel clock characteristics. The
validation uses 'clk_round_rate()' for each mode, which may introduce
additional delay (about 3.5 ms for 30 modes), but this is generally
negligible. Users desiring faster validation may bypass these calls
selectively, for example, checking only the highest resolution mode,
as shown here[1].

[1]: https://lore.kernel.org/all/20250704094851.182131-3-j-choudhary@ti.com/

Tested-by: Michael Walle <mwalle@kernel.org>
Reviewed-by: Devarsh Thakkar <devarsht@ti.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
Signed-off-by: Swamil Jain <s-jain1@ti.com>
Link: https://patch.msgid.link/20251104151422.307162-2-s-jain1@ti.com
[Tomi: dropped 'inline' from check_pixel_clock]
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Stable-dep-of: 86db652fc2 ("drm/tidss: Move OLDI mode validation to OLDI bridge mode_valid hook")
Signed-off-by: Sasha Levin <sashal@kernel.org>

...

This commit is contained in:

Jayesh Choudhary 2025-11-04 20:44:21 +05:30 • committed by Greg Kroah-Hartman

parent b2abcb8986

commit b1d4bb4369

2 changed files with 31 additions and 58 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

86

drivers/gpu/drm/tidss/tidss_dispc.c

View file

3

drivers/gpu/drm/tidss/tidss_dispc.h

View file