From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1E38217B418; Thu, 5 Mar 2026 15:26:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772724412; cv=none; b=Vz77qnkhwzzgMMV9AEwsWWjthwvOJAYDXMQV86Eg8+C6GJGGgrqhLDQigcfl+7IV8Qixj90NxBdZLBtQJ9eHd+SyG+kmbxFwoP8+FZGogYPf3jMA1ryOowMLCfKx4v3iUq9IBGDQmAkWPAgCbQpRZRRK9FHFt+lLNKUQDGTFYvA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772724412; c=relaxed/simple; bh=4Ph21YNHCyEvjo/bKXsJPUwpBDx3Z0UNvaVUS93jta4=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=WU+a0W/r7r5+ycwjTAVofiKuwLTWyKnDzcU+AF3LFBRJRVPz8HzdEUxvJmNGI3EfTJhgulLhTcMvjMJkgmc+9EPvXvQDoZdeAH98V+EnQ1RbJurUPyhaFMoYzQLAhnvcgQKV4J5HAPBqwMZW8omao23JZ87T18uZuPFpgB9w7rE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Lk41FGwK; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Lk41FGwK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 53A04C19423; Thu, 5 Mar 2026 15:26:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772724411; bh=4Ph21YNHCyEvjo/bKXsJPUwpBDx3Z0UNvaVUS93jta4=; h=From:To:Cc:Subject:Date:From; b=Lk41FGwK+FS+12m6ve1kB+572nNh9e3n0pHZe3KCtpj8K13JaGUU1r10n3KoWImzB GRbs/hhlO3fxTSSP7+FMqBXsv0Uz12FNZnIWBUtogJLKvSN34j981H4kjlVGDjC783 8D0A5rKf3nw/utRvuZ16dvWGAZ7cwA8Xy8lR3vIpin0/vk7v4x2IpZh+4VsA/pJfxK QQWzEcGfa8SleV/azMcKC/jF3GUTBSY7BfIp/hNTpEUEw5ZCD3Pa+STYcv6B8RAYoz fPC5oY1IwSi5wfiZsnaPWBVeJcGNlxcxES40ztC+5lUqMEtrD40Z9HoKgQqg+afifj tURebJhKNOf8g== From: Arnd Bergmann To: Detlev Casanova , Ezequiel Garcia , Mauro Carvalho Chehab , Heiko Stuebner , Nathan Chancellor , Nicolas Dufresne , Hans Verkuil Cc: Arnd Bergmann , Nick Desaulniers , Bill Wendling , Justin Stitt , Kees Cook , linux-media@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev Subject: [PATCH 1/2] [RESEND] media: rkvdec: reduce excessive stack usage in assemble_hw_pps() Date: Thu, 5 Mar 2026 16:26:16 +0100 Message-Id: <20260305152644.791897-1-arnd@kernel.org> X-Mailer: git-send-email 2.39.5 Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Arnd Bergmann The rkvdec_pps had a large set of bitfields, all of which as misaligned. This causes clang-21 and likely other versions to produce absolutely awful object code and a warning about very large stack usage, on targets without unaligned access: drivers/media/platform/rockchip/rkvdec/rkvdec-vp9.c:966:12: error: stack frame size (1472) exceeds limit (1280) in 'rkvdec_vp9_start' [-Werror,-Wframe-larger-than] Part of the problem here is how all the bitfield accesses are inlined into a function that already has large structures on the stack. Mark set_field_order_cnt() as noinline_for_stack, and split out the following accesses in assemble_hw_pps() into another noinline function, both of which now using around 800 bytes of stack in the same configuration. There is clearly still something wrong with clang here, but splitting it into multiple functions reduces the risk of stack overflow. Fixes: fde24907570d ("media: rkvdec: Add H264 support for the VDPU383 variant") Link: https://godbolt.org/z/acP1eKeq9 Reviewed-by: Nicolas Dufresne Signed-off-by: Arnd Bergmann --- Resending this along with the other patch mainly to point out that this one is still pending as well. --- .../rockchip/rkvdec/rkvdec-vdpu383-h264.c | 50 ++++++++++--------- 1 file changed, 27 insertions(+), 23 deletions(-) diff --git a/drivers/media/platform/rockchip/rkvdec/rkvdec-vdpu383-h264.c b/drivers/media/platform/rockchip/rkvdec/rkvdec-vdpu383-h264.c index 97f1efde2e47..fb4f849d7366 100644 --- a/drivers/media/platform/rockchip/rkvdec/rkvdec-vdpu383-h264.c +++ b/drivers/media/platform/rockchip/rkvdec/rkvdec-vdpu383-h264.c @@ -130,7 +130,7 @@ struct rkvdec_h264_ctx { struct vdpu383_regs_h26x regs; }; -static void set_field_order_cnt(struct rkvdec_pps *pps, const struct v4l2_h264_dpb_entry *dpb) +static noinline_for_stack void set_field_order_cnt(struct rkvdec_pps *pps, const struct v4l2_h264_dpb_entry *dpb) { pps->top_field_order_cnt0 = dpb[0].top_field_order_cnt; pps->bot_field_order_cnt0 = dpb[0].bottom_field_order_cnt; @@ -166,6 +166,31 @@ static void set_field_order_cnt(struct rkvdec_pps *pps, const struct v4l2_h264_d pps->bot_field_order_cnt15 = dpb[15].bottom_field_order_cnt; } +static noinline_for_stack void set_dec_params(struct rkvdec_pps *pps, const struct v4l2_ctrl_h264_decode_params *dec_params) +{ + const struct v4l2_h264_dpb_entry *dpb = dec_params->dpb; + + for (int i = 0; i < ARRAY_SIZE(dec_params->dpb); i++) { + if (dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM) + pps->is_longterm |= (1 << i); + pps->ref_field_flags |= + (!!(dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_FIELD)) << i; + pps->ref_colmv_use_flag |= + (!!(dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_ACTIVE)) << i; + pps->ref_topfield_used |= + (!!(dpb[i].fields & V4L2_H264_TOP_FIELD_REF)) << i; + pps->ref_botfield_used |= + (!!(dpb[i].fields & V4L2_H264_BOTTOM_FIELD_REF)) << i; + } + pps->pic_field_flag = + !!(dec_params->flags & V4L2_H264_DECODE_PARAM_FLAG_FIELD_PIC); + pps->pic_associated_flag = + !!(dec_params->flags & V4L2_H264_DECODE_PARAM_FLAG_BOTTOM_FIELD); + + pps->cur_top_field = dec_params->top_field_order_cnt; + pps->cur_bot_field = dec_params->bottom_field_order_cnt; +} + static void assemble_hw_pps(struct rkvdec_ctx *ctx, struct rkvdec_h264_run *run) { @@ -177,7 +202,6 @@ static void assemble_hw_pps(struct rkvdec_ctx *ctx, struct rkvdec_h264_priv_tbl *priv_tbl = h264_ctx->priv_tbl.cpu; struct rkvdec_sps_pps *hw_ps; u32 pic_width, pic_height; - u32 i; /* * HW read the SPS/PPS information from PPS packet index by PPS id. @@ -261,28 +285,8 @@ static void assemble_hw_pps(struct rkvdec_ctx *ctx, !!(pps->flags & V4L2_H264_PPS_FLAG_SCALING_MATRIX_PRESENT); set_field_order_cnt(&hw_ps->pps, dpb); + set_dec_params(&hw_ps->pps, dec_params); - for (i = 0; i < ARRAY_SIZE(dec_params->dpb); i++) { - if (dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM) - hw_ps->pps.is_longterm |= (1 << i); - - hw_ps->pps.ref_field_flags |= - (!!(dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_FIELD)) << i; - hw_ps->pps.ref_colmv_use_flag |= - (!!(dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_ACTIVE)) << i; - hw_ps->pps.ref_topfield_used |= - (!!(dpb[i].fields & V4L2_H264_TOP_FIELD_REF)) << i; - hw_ps->pps.ref_botfield_used |= - (!!(dpb[i].fields & V4L2_H264_BOTTOM_FIELD_REF)) << i; - } - - hw_ps->pps.pic_field_flag = - !!(dec_params->flags & V4L2_H264_DECODE_PARAM_FLAG_FIELD_PIC); - hw_ps->pps.pic_associated_flag = - !!(dec_params->flags & V4L2_H264_DECODE_PARAM_FLAG_BOTTOM_FIELD); - - hw_ps->pps.cur_top_field = dec_params->top_field_order_cnt; - hw_ps->pps.cur_bot_field = dec_params->bottom_field_order_cnt; } static void rkvdec_write_regs(struct rkvdec_ctx *ctx) -- 2.39.5