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 1914A2DC337; Mon, 2 Feb 2026 09:48:11 +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=1770025692; cv=none; b=jw0hfNJAHDtKhQC3r2igRKxy5KiVXZAOtjuvGpCIC3PAGIJZQL12LVhf3JELmbbtKEA0JOocuLhAFmbCjWErZRRE3uqwNzw6VUTM3W9bdV13aO/lIXNLGHV/P9qgjvzuEeviYJSWqFSMBNlBVfsfXR7mI1an6jMLWWGaxdfD/iw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770025692; c=relaxed/simple; bh=5K6vbILKfAvsEfbhV3qaRciVW+JYPHJcTO2mdlMYeV8=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=MLJzyA7L5yIuWVcpqiiaGkVIexKAUwjcFtMlW4wGOxGTk6+yPX0fpjbVrkGqbQ+3gtMAf+YjZu4PnpMz6jZ5OeB+OXH91BXtwwJikfPfRYN/mg3G2qSL1Ww73raYt+GwUQ8TQfOpJ6+/i+j/pFJDhVtLCeeSXOAh+9wvMDU2wAw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JaYKlSvk; 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="JaYKlSvk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5F7A2C116C6; Mon, 2 Feb 2026 09:48:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770025691; bh=5K6vbILKfAvsEfbhV3qaRciVW+JYPHJcTO2mdlMYeV8=; h=From:To:Cc:Subject:Date:From; b=JaYKlSvkBgwpyt18cqC58hmzMQAtKrYA0gMA4zs39L6yQ34SAB+08BawaTPzvBAVx XEYAYeVC+AmTN7NogCCwmxQHOsaou4TjfApzF5KWPZUs7oItfujKkVWE+mzB9k0qsV Vk7Sx9gRp6bkmfsShGLXPgpoU0je6hNLZG6B8OyZvkopl76b5GyaGnn48Nbh2kvgpt GIv9w6WHg6LbYXhPTjHerHxmNCRVqgLZClyz9hXkdKgWuBzWvY8s++EncVYSpqPW+5 rpWaXcSHhusqtX7o71o8y/vylqjlDnCoMLQE65R+75lH5+ohyV5LRN2qreuBt28zbr F6pI8LR2ywRuA== 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 , 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] media: rkvdec: reduce excessive stack usage in assemble_hw_pps() Date: Mon, 2 Feb 2026 10:47:50 +0100 Message-Id: <20260202094804.1231706-1-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 Signed-off-by: Arnd Bergmann --- .../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 6ab3167addc8..ef69f2a36478 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