From 106b4a2a78b2a2f14885604891957b84bba502db Mon Sep 17 00:00:00 2001 From: Adrian Betschart Date: Fri, 11 Sep 2026 17:13:14 +0200 Subject: drm/amd/display: Try RGB before YCbCr 4:4:4 in stream validation amdgpu_dm_create_validate_stream_for_sink() walks encoding_order[] and uses the first encoding that validates. YCbCr 4:4:4 is listed before RGB, so an HDMI sink that advertises 4:4:4 gets YCbCr 4:4:4 whenever the "color format" property is left at AUTO, even though RGB fits the same link. That contradicts the documented AUTO behaviour for HDMI in enum drm_connector_color_format (RGB, falling back to YCbCr 4:2:0 only when the bandwidth is not available or the mode is 4:2:0-only), which the amdgpu implementation of the property also describes. It also leaves the "Broadcast RGB" property without effect on such sinks, since the quantization range it selects only applies to RGB output. Try RGB first. The mask still holds every encoding the sink supports, so a mode that cannot carry RGB falls back exactly as before. For reference, v7.2 picked RGB here unless YCbCr 4:4:4 was forced through debugfs, while earlier kernels picked YCbCr 4:4:4 for any HDMI sink that advertised it. Fixes: 0b0ff65d3ca1 ("drm/amd/display: Refactor stream validation") Suggested-by: Adolfo Rodrigues Assisted-by: Claude Code:claude-fable-5-1 Signed-off-by: Adrian Betschart Reviewed-by: Fangzhi Zuo Tested-by: Adolfo Rodrigues Tested-by: Daniel Wheeler Signed-off-by: Alex Deucher (cherry picked from commit 7de432bc753133764dc40d37f9388da56de251e7) --- lib/sg_split.c | 199 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 199 insertions(+) create mode 100644 lib/sg_split.c (limited to 'lib/sg_split.c') diff --git a/lib/sg_split.c b/lib/sg_split.c new file mode 100644 index 000000000..24e8f5e48 --- /dev/null +++ b/lib/sg_split.c @@ -0,0 +1,199 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2015 Robert Jarzmik + * + * Scatterlist splitting helpers. + */ + +#include +#include + +struct sg_splitter { + struct scatterlist *in_sg0; + int nents; + off_t skip_sg0; + unsigned int length_last_sg; + + struct scatterlist *out_sg; +}; + +static int sg_calculate_split(struct scatterlist *in, int nents, int nb_splits, + off_t skip, const size_t *sizes, + struct sg_splitter *splitters, bool mapped) +{ + int i; + unsigned int sglen; + size_t size = sizes[0], len; + struct sg_splitter *curr = splitters; + struct scatterlist *sg; + + for (i = 0; i < nb_splits; i++) { + splitters[i].in_sg0 = NULL; + splitters[i].nents = 0; + } + + for_each_sg(in, sg, nents, i) { + sglen = mapped ? sg_dma_len(sg) : sg->length; + if (skip > sglen) { + skip -= sglen; + continue; + } + + len = min_t(size_t, size, sglen - skip); + if (!curr->in_sg0) { + curr->in_sg0 = sg; + curr->skip_sg0 = skip; + } + size -= len; + curr->nents++; + curr->length_last_sg = len; + + while (!size && (skip + len < sglen) && (--nb_splits > 0)) { + curr++; + size = *(++sizes); + skip += len; + len = min_t(size_t, size, sglen - skip); + + curr->in_sg0 = sg; + curr->skip_sg0 = skip; + curr->nents = 1; + curr->length_last_sg = len; + size -= len; + } + skip = 0; + + if (!size && --nb_splits > 0) { + curr++; + size = *(++sizes); + } + + if (!nb_splits) + break; + } + + return (size || !splitters[0].in_sg0) ? -EINVAL : 0; +} + +static void sg_split_phys(struct sg_splitter *splitters, const int nb_splits) +{ + int i, j; + struct scatterlist *in_sg, *out_sg; + struct sg_splitter *split; + + for (i = 0, split = splitters; i < nb_splits; i++, split++) { + in_sg = split->in_sg0; + out_sg = split->out_sg; + for (j = 0; j < split->nents; j++, out_sg++) { + *out_sg = *in_sg; + if (!j) { + out_sg->offset += split->skip_sg0; + out_sg->length -= split->skip_sg0; + } + sg_dma_address(out_sg) = 0; + sg_dma_len(out_sg) = 0; + in_sg = sg_next(in_sg); + } + out_sg[-1].length = split->length_last_sg; + sg_mark_end(out_sg - 1); + } +} + +static void sg_split_mapped(struct sg_splitter *splitters, const int nb_splits) +{ + int i, j; + struct scatterlist *in_sg, *out_sg; + struct sg_splitter *split; + + for (i = 0, split = splitters; i < nb_splits; i++, split++) { + in_sg = split->in_sg0; + out_sg = split->out_sg; + for (j = 0; j < split->nents; j++, out_sg++) { + sg_dma_address(out_sg) = sg_dma_address(in_sg); + sg_dma_len(out_sg) = sg_dma_len(in_sg); + if (!j) { + sg_dma_address(out_sg) += split->skip_sg0; + sg_dma_len(out_sg) -= split->skip_sg0; + } + in_sg = sg_next(in_sg); + } + sg_dma_len(--out_sg) = split->length_last_sg; + } +} + +/** + * sg_split - split a scatterlist into several scatterlists + * @in: the input sg list + * @in_mapped_nents: the result of a dma_map_sg(in, ...), or 0 if not mapped. + * @skip: the number of bytes to skip in the input sg list + * @nb_splits: the number of desired sg outputs + * @split_sizes: the respective size of each output sg list in bytes + * @out: an array where to store the allocated output sg lists + * @out_mapped_nents: the resulting sg lists mapped number of sg entries. Might + * be NULL if sglist not already mapped (in_mapped_nents = 0) + * @gfp_mask: the allocation flag + * + * This function splits the input sg list into nb_splits sg lists, which are + * allocated and stored into out. + * The @in is split into : + * - @out[0], which covers bytes [@skip .. @skip + @split_sizes[0] - 1] of @in + * - @out[1], which covers bytes [@skip + split_sizes[0] .. + * @skip + @split_sizes[0] + @split_sizes[1] -1] + * etc ... + * It will be the caller's duty to kfree() out array members. + * + * Returns 0 upon success, or error code + */ +int sg_split(struct scatterlist *in, const int in_mapped_nents, + const off_t skip, const int nb_splits, + const size_t *split_sizes, + struct scatterlist **out, int *out_mapped_nents, + gfp_t gfp_mask) +{ + int i, ret; + struct sg_splitter *splitters; + + splitters = kzalloc_objs(*splitters, nb_splits, gfp_mask); + if (!splitters) + return -ENOMEM; + + ret = sg_calculate_split(in, sg_nents(in), nb_splits, skip, split_sizes, + splitters, false); + if (ret < 0) + goto err; + + ret = -ENOMEM; + for (i = 0; i < nb_splits; i++) { + splitters[i].out_sg = kmalloc_objs(struct scatterlist, + splitters[i].nents, gfp_mask); + if (!splitters[i].out_sg) + goto err; + } + + /* + * The order of these 3 calls is important and should be kept. + */ + sg_split_phys(splitters, nb_splits); + if (in_mapped_nents) { + ret = sg_calculate_split(in, in_mapped_nents, nb_splits, skip, + split_sizes, splitters, true); + if (ret < 0) + goto err; + sg_split_mapped(splitters, nb_splits); + } + + for (i = 0; i < nb_splits; i++) { + out[i] = splitters[i].out_sg; + if (out_mapped_nents) + out_mapped_nents[i] = splitters[i].nents; + } + + kfree(splitters); + return 0; + +err: + for (i = 0; i < nb_splits; i++) + kfree(splitters[i].out_sg); + kfree(splitters); + return ret; +} +EXPORT_SYMBOL(sg_split); -- cgit v1.3.1