lwn.git/drivers/gpu/drm/sun4i/sun8i_mixer.c, branch docs-fixes

drm/sun4i: Use backend/mixer as dedicated DMA device

2026-03-23T05:23:29+00:00

The sun4i DRM driver deals with DMA constraints in a peculiar way. Instead of using the actual DMA device in various helpers, it justs reconfigures the DMA constraints of the virtual display device using the DMA device's device tree node by calling of_dma_configure(). Turns out of_dma_configure() should only be called from bus code. Lately this also triggers a big warning through of_iommu_configure() and ultimately __iommu_probe_device(): late IOMMU probe at driver bind, something fishy here! Now that the GEM DMA helpers have proper support for allocating and mapping buffers with a dedicated DMA device, switch over to it as the proper solution. The mixer change was tested on a Pine H64 model B. The backend change was only compile tested. Though I don't expect any issues, help testing on an older device would be appreciated. Acked-by: Jernej Skrabec Link: https://patch.msgid.link/20260311094929.3393338-5-wenst@chromium.org Signed-off-by: Chen-Yu Tsai

drm/sun4i: mixer: Fix layer init code

2026-02-24T17:37:34+00:00

Code refactoring dropped extra NULL sentinel entry at the end of the drm planes array. Add it back. Reported-by: Chen-Yu Tsai Closes: https://lore.kernel.org/linux-sunxi/CAGb2v65wY2pF6sR+0JgnpLa4ysvjght5hAKDa1RUyo=zEKXreg@mail.gmail.com/ Fixes: 4fa45b04a47d ("drm/sun4i: layer: move num of planes calc out of layer code") Signed-off-by: Jernej Skrabec Reviewed-by: Chen-Yu Tsai Link: https://patch.msgid.link/20260218183454.7881-1-jernej.skrabec@gmail.com [wens@kernel.org: Fix "Fixes" commit hash] Signed-off-by: Chen-Yu Tsai

drm/sun4i: Nuke mixer pointer from layer code

2025-11-12T09:18:25+00:00

It's not used anymore, so remove it. This allows trully independent layer state from mixer. Reviewed-by: Chen-Yu Tsai Tested-by: Ryan Walklin Signed-off-by: Jernej Skrabec Link: https://patch.msgid.link/20251104180942.61538-31-jernej.skrabec@gmail.com Signed-off-by: Chen-Yu Tsai

drm/sun4i: layer: replace mixer with layer struct

2025-11-12T09:18:25+00:00

This allows to almost completely decouple layer code from mixer. This is important for DE33. Reviewed-by: Chen-Yu Tsai Tested-by: Ryan Walklin Signed-off-by: Jernej Skrabec Link: https://patch.msgid.link/20251104180942.61538-29-jernej.skrabec@gmail.com Signed-off-by: Chen-Yu Tsai

drm/sun4i: mixer: split out layer config

2025-11-12T09:18:25+00:00

Later special plane only driver for DE33 will provide separate configuration. This change will also help layer driver migrate away from mixer structure. Reviewed-by: Chen-Yu Tsai Tested-by: Ryan Walklin Signed-off-by: Jernej Skrabec Link: https://patch.msgid.link/20251104180942.61538-28-jernej.skrabec@gmail.com Signed-off-by: Chen-Yu Tsai

drm/sun4i: mixer: Add quirk for number of VI scalers

2025-11-12T09:18:25+00:00

On DE2 and DE3, UI scalers are located right after VI scalers. So in order to calculate proper UI scaler base address, number of VI scalers must be known. In practice, it is same as number of VI channels, but it doesn't need to be. Let's make a quirk for this number. Code for configuring channels and associated functions won't have access to vi_num quirk anymore after rework for independent planes. Reviewed-by: Chen-Yu Tsai Tested-by: Ryan Walklin Signed-off-by: Jernej Skrabec Link: https://patch.msgid.link/20251104180942.61538-27-jernej.skrabec@gmail.com Signed-off-by: Chen-Yu Tsai

drm/sun4i: mixer: Convert heuristics to quirk

2025-11-12T09:18:24+00:00

Determination if FCC unit can be used for VI layer alpha depends on number of VI channels. This info won't be available anymore in future to VI layer driver because of DE33 way of allocating planes from same pool to different mixers. While order is slightly changed, it doesn't affect anything due to double buffering of registers. New order keeps related registers together and quirk separate. Reviewed-by: Chen-Yu Tsai Tested-by: Ryan Walklin Signed-off-by: Jernej Skrabec Link: https://patch.msgid.link/20251104180942.61538-25-jernej.skrabec@gmail.com Signed-off-by: Chen-Yu Tsai

drm/sun4i: layers: add physical index arg

2025-11-12T09:18:23+00:00

This avoids plane mapping in layers code, which allows future refactoring, when layer code will move away from accessing mixer structure. Reviewed-by: Chen-Yu Tsai Tested-by: Ryan Walklin Signed-off-by: Jernej Skrabec Link: https://patch.msgid.link/20251104180942.61538-23-jernej.skrabec@gmail.com Signed-off-by: Chen-Yu Tsai

drm/sun4i: layers: Make regmap for layers configurable

2025-11-12T09:18:23+00:00

Till DE33, there were no reason to decouple registers from mixer. However, with future new plane driver, this will be necessary. Reviewed-by: Chen-Yu Tsai Tested-by: Ryan Walklin Signed-off-by: Jernej Skrabec Link: https://patch.msgid.link/20251104180942.61538-21-jernej.skrabec@gmail.com Signed-off-by: Chen-Yu Tsai

drm/sun4i: layer: move num of planes calc out of layer code

2025-11-12T09:18:22+00:00

With DE33, number of planes no longer depends on mixer because layers are shared between all mixers. Get this value via parameter, so DE specific code can fill in proper value. Reviewed-by: Chen-Yu Tsai Tested-by: Ryan Walklin Signed-off-by: Jernej Skrabec Link: https://patch.msgid.link/20251104180942.61538-16-jernej.skrabec@gmail.com Signed-off-by: Chen-Yu Tsai