From patchwork Tue Oct 24 10:22:17 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Imre Deak X-Patchwork-Id: 13434189 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6030BC25B47 for ; Tue, 24 Oct 2023 10:22:05 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7981F10E320; Tue, 24 Oct 2023 10:21:55 +0000 (UTC) Received: from mgamail.intel.com (mgamail.intel.com [192.55.52.43]) by gabe.freedesktop.org (Postfix) with ESMTPS id 67D5310E31C; Tue, 24 Oct 2023 10:21:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1698142913; x=1729678913; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=zMKYhrDM/vW6moOvi9XD9ZbizjNn1UA0fTDC3ROS5MY=; b=MYe82knuzmry6wO65B86dPApeo8exKWwteVH0obz+aAveT6o/e6L1H6T X+b+pgjyeJRiTAWwzLoKCYzxV2EdwrexG8cs40Dv6tCOZQcoa61S3fBgO 4JV9VnkDnd9iFbv51xvrPlZNfZOA7ENMP4n3o29tfGFNbmCBgUKw8/CCK A/5wK6ttKeJJgkAiTuLTvHzZe3JZb3uPEB1FXpvIB/AvQEw+ryRB2Q7H2 qWDU7qu6Q0WpUriwzvoeTqfDhAnd3OXihh0tyJwGcFpH9vinVFeNJj2xC Ct5kZwmFvx89OHwBRB0sU3EZHxwGmTYASFTCkXQUQuaCWmYtIiGCnYOon g==; X-IronPort-AV: E=McAfee;i="6600,9927,10872"; a="473251952" X-IronPort-AV: E=Sophos;i="6.03,247,1694761200"; d="scan'208";a="473251952" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Oct 2023 03:21:53 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10872"; a="902118299" X-IronPort-AV: E=Sophos;i="6.03,247,1694761200"; d="scan'208";a="902118299" Received: from ideak-desk.fi.intel.com ([10.237.72.78]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Oct 2023 03:19:31 -0700 From: Imre Deak To: intel-gfx@lists.freedesktop.org Date: Tue, 24 Oct 2023 13:22:17 +0300 Message-Id: <20231024102219.4035939-2-imre.deak@intel.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20231024010925.3949910-9-imre.deak@intel.com> References: <20231024010925.3949910-9-imre.deak@intel.com> MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH v2 08/29] drm/dp: Add helpers to calculate the link BW overhead X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: dri-devel@lists.freedesktop.org Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Add helpers drivers can use to calculate the BW allocation overhead - due to SSC, FEC, DSC and data alignment on symbol cycles - and the channel coding efficiency - due to the 8b/10b, 128b/132b encoding. On 128b/132b links the FEC overhead is part of the coding efficiency, so not accounted for in the BW allocation overhead. The drivers can use these functions to calculate a ratio, controlling the stream symbol insertion rate of the source device in each SST TU or MST MTP frame. Drivers can calculate this m/n = (pixel_data_rate * drm_dp_bw_overhead()) / (link_data_rate * drm_dp_bw_channel_coding_efficiency()) ratio for a given link and pixel stream and with that the mtp_count = CEIL(64 * m / n) allocated MTPs for the stream in a link frame and pbn = CEIL(64 * dm_mst_get_pbn_divider() * m / n) allocated PBNs for the stream on the MST link path. Take drm_dp_bw_overhead() into use in drm_dp_calc_pbn_mode(), for drivers calculating the PBN value directly. v2: - Add dockbook description to drm_dp_bw_channel_coding_efficiency(). (LKP). - Clarify the way m/n ratio is calculated in the commit log. Cc: Lyude Paul Cc: kernel test robot Cc: dri-devel@lists.freedesktop.org Signed-off-by: Imre Deak Reviewed-by: Stanislav Lisovskiy --- drivers/gpu/drm/display/drm_dp_helper.c | 124 ++++++++++++++++++ drivers/gpu/drm/display/drm_dp_mst_topology.c | 23 +++- include/drm/display/drm_dp_helper.h | 11 ++ 3 files changed, 152 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c index e5d7970a9ddd0..79629bf7547bf 100644 --- a/drivers/gpu/drm/display/drm_dp_helper.c +++ b/drivers/gpu/drm/display/drm_dp_helper.c @@ -3899,4 +3899,128 @@ int drm_panel_dp_aux_backlight(struct drm_panel *panel, struct drm_dp_aux *aux) } EXPORT_SYMBOL(drm_panel_dp_aux_backlight); +/* See DP Standard v2.1 2.6.4.4.1.1, 2.8.4.4, 2.8.7 */ +static int drm_dp_link_symbol_cycles(int lane_count, int pixels, int bpp_x16, + int symbol_size, bool is_mst) +{ + int cycles = DIV_ROUND_UP(pixels * bpp_x16, 16 * symbol_size * lane_count); + int align = is_mst ? 4 / lane_count : 1; + + return ALIGN(cycles, align); +} + +static int drm_dp_link_dsc_symbol_cycles(int lane_count, int pixels, int slice_count, + int bpp_x16, int symbol_size, bool is_mst) +{ + int slice_pixels = DIV_ROUND_UP(pixels, slice_count); + int slice_data_cycles = drm_dp_link_symbol_cycles(lane_count, slice_pixels, + bpp_x16, symbol_size, is_mst); + int slice_eoc_cycles = is_mst ? 4 / lane_count : 1; + + return slice_count * (slice_data_cycles + slice_eoc_cycles); +} + +/** + * drm_dp_bw_overhead - Calculate the BW overhead of a DP link stream + * @lane_count: DP link lane count + * @hactive: pixel count of the active period in one scanline of the stream + * @dsc_slice_count: DSC slice count if @flags/DRM_DP_LINK_BW_OVERHEAD_DSC is set + * @bpp_x16: bits per pixel in .4 binary fixed point + * @flags: DRM_DP_OVERHEAD_x flags + * + * Calculate the BW allocation overhead of a DP link stream, depending + * on the link's + * - @lane_count + * - SST/MST mode (@flags / %DRM_DP_OVERHEAD_MST) + * - symbol size (@flags / %DRM_DP_OVERHEAD_UHBR) + * - FEC mode (@flags / %DRM_DP_OVERHEAD_FEC) + * - SSC mode (@flags / %DRM_DP_OVERHEAD_SSC) + * as well as the stream's + * - @hactive timing + * - @bpp_x16 color depth + * - compression mode (@flags / %DRM_DP_OVERHEAD_DSC). + * Note that this overhead doesn't account for the 8b/10b, 128b/132b + * channel coding efficiency, for that see + * @drm_dp_link_bw_channel_coding_efficiency(). + * + * Returns the overhead as 100% + overhead% in 1ppm units. + */ +int drm_dp_bw_overhead(int lane_count, int hactive, + int dsc_slice_count, + int bpp_x16, unsigned long flags) +{ + int symbol_size = flags & DRM_DP_BW_OVERHEAD_UHBR ? 32 : 8; + bool is_mst = flags & DRM_DP_BW_OVERHEAD_MST; + u32 overhead = 1000000; + int symbol_cycles; + + /* + * DP Standard v2.1 2.6.4.1 + * SSC downspread and ref clock variation margin: + * 5300ppm + 300ppm ~ 0.6% + */ + if (flags & DRM_DP_BW_OVERHEAD_SSC) + overhead += 6000; + + /* + * DP Standard v2.1 2.6.4.1.1: + * FEC symbol insertions for 8b/10b channel coding: + * 2.4% + */ + if (flags & DRM_DP_BW_OVERHEAD_FEC) + overhead += 24000; + + /* + * DP Standard v2.1 2.7.9, 5.9.7 + * The FEC overhead for UHBR is accounted for in its 96.71% channel + * coding efficiency. + */ + WARN_ON((flags & DRM_DP_BW_OVERHEAD_UHBR) && + (flags & DRM_DP_BW_OVERHEAD_FEC)); + + if (flags & DRM_DP_BW_OVERHEAD_DSC) + symbol_cycles = drm_dp_link_dsc_symbol_cycles(lane_count, hactive, + dsc_slice_count, + bpp_x16, symbol_size, + is_mst); + else + symbol_cycles = drm_dp_link_symbol_cycles(lane_count, hactive, + bpp_x16, symbol_size, + is_mst); + + return DIV_ROUND_UP_ULL(mul_u32_u32(symbol_cycles * symbol_size * lane_count, + overhead * 16), + hactive * bpp_x16); +} +EXPORT_SYMBOL(drm_dp_bw_overhead); + +/** + * drm_dp_bw_channel_coding_efficiency - Get a DP link's channel coding efficiency + * @is_uhbr: Whether the link has a 128b/132b channel coding + * + * Return the channel coding efficiency of the given DP link type, which is + * either 8b/10b or 128b/132b (aka UHBR). The corresponding overhead includes + * the 8b -> 10b, 128b -> 132b pixel data to link symbol conversion overhead + * and for 128b/132b any link or PHY level control symbol insertion overhead + * (LLCP, FEC, PHY sync, see DP Standard v2.1 3.5.2.18). For 8b/10b the + * corresponding FEC overhead is BW allocation specific, included in the value + * returned by drm_dp_bw_overhead(). + * + * Returns the efficiency in the 100%/coding-overhead% ratio in + * 1ppm units. + */ +int drm_dp_bw_channel_coding_efficiency(bool is_uhbr) +{ + if (is_uhbr) + return 967100; + else + /* + * Note that on 8b/10b MST the efficiency is only + * 78.75% due to the 1 out of 64 MTPH packet overhead, + * not accounted for here. + */ + return 800000; +} +EXPORT_SYMBOL(drm_dp_bw_channel_coding_efficiency); + #endif diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c index cc0a8fe84d290..d7383f2fd6cfe 100644 --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c @@ -4726,17 +4726,28 @@ EXPORT_SYMBOL(drm_dp_check_act_status); int drm_dp_calc_pbn_mode(int clock, int bpp) { /* - * margin 5300ppm + 300ppm ~ 0.6% as per spec, factor is 1.006 * The unit of 54/64Mbytes/sec is an arbitrary unit chosen based on * common multiplier to render an integer PBN for all link rate/lane * counts combinations * calculate - * peak_kbps *= (1006/1000) - * peak_kbps *= (64/54) - * peak_kbps *= 8 convert to bytes + * peak_kbps = clock * bpp / 16 + * peak_kbps *= SSC overhead / 1000000 + * peak_kbps /= 8 convert to Kbytes + * peak_kBps *= (64/54) / 1000 convert to PBN */ - return DIV_ROUND_UP_ULL(mul_u32_u32(clock * bpp, 64 * 1006 >> 4), - 1000 * 8 * 54 * 1000); + /* + * TODO: Use the actual link and mode parameters to calculate + * the overhead. For now it's assumed that these are + * 4 link lanes, 4096 hactive pixels, which don't add any + * significant data padding overhead and that there is no DSC + * or FEC overhead. + */ + int overhead = drm_dp_bw_overhead(4, 4096, 0, bpp, + DRM_DP_BW_OVERHEAD_MST | + DRM_DP_BW_OVERHEAD_SSC); + + return DIV64_U64_ROUND_UP(mul_u32_u32(clock * bpp, 64 * overhead >> 4), + 1000000ULL * 8 * 54 * 1000); } EXPORT_SYMBOL(drm_dp_calc_pbn_mode); diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h index da94932f4262b..d0f7406c510a8 100644 --- a/include/drm/display/drm_dp_helper.h +++ b/include/drm/display/drm_dp_helper.h @@ -788,4 +788,15 @@ bool drm_dp_downstream_rgb_to_ycbcr_conversion(const u8 dpcd[DP_RECEIVER_CAP_SIZ const u8 port_cap[4], u8 color_spc); int drm_dp_pcon_convert_rgb_to_ycbcr(struct drm_dp_aux *aux, u8 color_spc); +#define DRM_DP_BW_OVERHEAD_MST BIT(0) +#define DRM_DP_BW_OVERHEAD_UHBR BIT(1) +#define DRM_DP_BW_OVERHEAD_SSC BIT(2) +#define DRM_DP_BW_OVERHEAD_FEC BIT(3) +#define DRM_DP_BW_OVERHEAD_DSC BIT(4) + +int drm_dp_bw_overhead(int lane_count, int hactive, + int dsc_slice_count, + int bpp_x16, unsigned long flags); +int drm_dp_bw_channel_coding_efficiency(bool is_uhbr); + #endif /* _DRM_DP_HELPER_H_ */