This series contains a pile of patches that was created to support hooking up the AUO B116XAK01 panel to the eDP side of the bridge. In general it should be useful for hooking up a wider variety of DP panels to the bridge, especially those with lower resolution and lower bits per pixel.
The overall result of this series: * Allows panels with fewer than 4 DP lanes hooked up to work. * Optimizes the link rate for panels with 6 bpp. * Supports trying more than one link rate when training if the main link rate didn't work. * Avoids invalid link rates.
It's not expected that this series will break any existing users but testing is always good.
To support the AUO B116XAK01, we could actually stop at the ("Use 18-bit DP if we can") patch since that causes the panel to run at a link rate of 1.62 which works. The patches to try more than one link rate were all developed prior to realizing that I could just use 18-bit mode and were validated with that patch reverted.
These patches were tested on sdm845-cheza atop mainline as of 2019-12-13 and also on another board (the one with AUO B116XAK01) atop a downstream kernel tree.
This patch series doesn't do anything to optimize the MIPI link and only focuses on the DP link. For instance, it's left as an exercise to the reader to see if we can use the 666-packed mode on the MIPI link and save some power (because we could lower the clock rate).
I am nowhere near a display expert and my knowledge of DP and MIPI is pretty much zero. If something about this patch series smells wrong, it probably is. Please let know and I'll try to fix it.
Changes in v3: - Init rate_valid table, don't rely on stack being 0 (oops). - Rename rate_times_200khz to rate_per_200khz. - Loop over the ti_sn_bridge_dp_rate_lut table, making code smaller. - Use 'true' instead of 1 for bools. - Added note to commit message noting DP 1.4+ isn't well tested.
Changes in v2: - Squash in maybe-uninitialized fix from Rob Clark. - Patch ("Avoid invalid rates") replaces ("Skip non-standard DP rates")
Douglas Anderson (9): drm/bridge: ti-sn65dsi86: Split the setting of the dp and dsi rates drm/bridge: ti-sn65dsi86: zero is never greater than an unsigned int drm/bridge: ti-sn65dsi86: Don't use MIPI variables for DP link drm/bridge: ti-sn65dsi86: Config number of DP lanes Mo' Betta drm/bridge: ti-sn65dsi86: Read num lanes from the DP sink drm/bridge: ti-sn65dsi86: Use 18-bit DP if we can drm/bridge: ti-sn65dsi86: Group DP link training bits in a function drm/bridge: ti-sn65dsi86: Train at faster rates if slower ones fail drm/bridge: ti-sn65dsi86: Avoid invalid rates
drivers/gpu/drm/bridge/ti-sn65dsi86.c | 259 +++++++++++++++++++++----- 1 file changed, 216 insertions(+), 43 deletions(-)