From mboxrd@z Thu Jan 1 00:00:00 1970 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 CBA71C54F4D for ; Tue, 28 Jul 2026 15:11:23 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 8704D10E6E9; Tue, 28 Jul 2026 15:11:23 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="UpoKd5Bg"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.13]) by gabe.freedesktop.org (Postfix) with ESMTPS id A7BDB10E5A3; Tue, 28 Jul 2026 15:11:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1785251482; x=1816787482; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=I/1plry/2iUlcW7p43kVxGeN9TyaQxXIEiD3BalWjPc=; b=UpoKd5BghsVzmmvtwy8rk005BVrA6FjVD/OYhx8utzFPpT4+zlO6wmp4 HpH4CbY3AKVLNGt6hy6mRKli8vphLck7mRvedWLwvet2EKL5U7biVDaVi yz2Fw0DFSOd08YLM5LP1JDImeYduYGTwTpdLC9w/Dy3Q8Mk26JnnuufTV 3qsc9MLeGsdVCutD1bFlTmQfs/5aa2FNAEw1x7cCJy4dnG/33oLwA9R4w i+6cSNwRQqe+QMFdbkuZXAjKKdgjPV/5IOx19RZuC0x6VKKTGHVbdr7aa g6O8wA5jCFUAUXV7g8XA95RzgG4nItEOk/715I6cJse97o9Q4+ioWiKpD g==; X-CSE-ConnectionGUID: DwJAsvAgQSCvfAu/k2ZjKw== X-CSE-MsgGUID: WdufLD02ShyGg/l4jrv3Eg== X-IronPort-AV: E=McAfee;i="6800,10657,11859"; a="88376940" X-IronPort-AV: E=Sophos;i="6.25,190,1779174000"; d="scan'208";a="88376940" Received: from fmviesa003.fm.intel.com ([10.60.135.143]) by fmvoesa107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Jul 2026 08:10:08 -0700 X-CSE-ConnectionGUID: aZioPwjCQRSKxQ2GC346SQ== X-CSE-MsgGUID: u+Y7QQRkS0+IOwG2BwqXnA== X-ExtLoop1: 1 Received: from mgolanimitul-x299-ud4-pro.iind.intel.com ([10.190.239.114]) by fmviesa003.fm.intel.com with ESMTP; 28 Jul 2026 08:10:06 -0700 From: Mitul Golani To: intel-gfx@lists.freedesktop.org Cc: intel-xe@lists.freedesktop.org, uma.shankar@intel.com, ankit.k.nautiyal@intel.com, chaitanya.kumar.borah@intel.com Subject: [PATCH v7 06/10] drm/i915/vrr: Compute CMRR fractional timings generically Date: Tue, 28 Jul 2026 20:29:38 +0530 Message-ID: <20260728145943.3848704-7-mitulkumar.ajitkumar.golani@intel.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20260728145943.3848704-1-mitulkumar.ajitkumar.golani@intel.com> References: <20260728145943.3848704-1-mitulkumar.ajitkumar.golani@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" Rework the fractional CMRR computation into a generic, transcoder-agnostic helper driven by an explicit per-CRTC debugfs target, replacing the previous disabled, eDP-only code path. Compute CMRR_M and CMRR_N timings based on the video mode requirements. Note that the CMRR enable path is wired up separately; this patch only lays down the generic computation. Remove computation of mode_flags, I915_MODE_FLAG_VRR, as CMRR is being moved to the fixed refresh rate path. Also return early from the CMRR computation if the existing computation is already sufficient. --v2: - Derive video_mode locally instead of caching it in the persistent struct intel_crtc state (Jani, Chaitanya) - Fix numerator unit in comment: milli-Hz, not kHz (Chaitanya) - Fix "requirement" typo and clarify that CMRR is not yet enabled in the commit message (Chaitanya) - Fix precision issue while computing the M/N ratio (Chaitanya) - Rename multiplier_m and multiplier_n to improve readability (Chaitanya) - Compute vtotal as it is required for dithering as per the algorithm implementation (Chaitanya) - Replace the misleading adjusted_pixel_rate with dividend, which is more descriptive --v3: - Mention the rationale for not computing I915_MODE_FLAG_VRR (Chaitanya) - Remove the redundant return statement at the end of the CMRR computation (Chaitanya) - Correct cmrr_n calculation (Chaitanya) - Add an early return if the current computation is already sufficient to drive the mode without CMRR (Chaitanya) - Round up requested_refresh_rate (Validation) - Fix integer overflow --v4: - Update cmrr_n calculation to avoid aggressive dithering - Use div64_u64 to truncate to the floor value instead of DIV_ROUND_UP_ULL, which rounds up to the ceiling value - Add a TODO comment to the cmrr_n calculation - Add a condition for custom refresh rate requests - Update the CMRR computation comment block in compute_config --v5: - Simplify computation - Correct typo in commit message (Chaitanya) - Compute early return condition (Chaitanya) Signed-off-by: Mitul Golani --- drivers/gpu/drm/i915/display/intel_vrr.c | 143 ++++++++++++----------- 1 file changed, 78 insertions(+), 65 deletions(-) diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c index 6d3333fd5281..7746b2ead7d1 100644 --- a/drivers/gpu/drm/i915/display/intel_vrr.c +++ b/drivers/gpu/drm/i915/display/intel_vrr.c @@ -27,9 +27,6 @@ #include "skl_prefill.h" #include "skl_watermark.h" -#define FIXED_POINT_PRECISION 100 -#define CMRR_PRECISION_TOLERANCE 10 - /* * Tunable parameters for DC Balance correction. * These are captured based on experimentations. @@ -198,68 +195,86 @@ static bool intel_vrr_cmrr_possible(const struct intel_crtc_state *crtc_state) return HAS_CMRR(display) && intel_vrr_always_use_vrr_tg(display); } -static bool -is_cmrr_frac_required(struct intel_crtc_state *crtc_state) +static void +intel_vrr_cmrr_compute_config(struct intel_crtc_state *crtc_state) { - int calculated_refresh_k, actual_refresh_k, pixel_clock_per_line; + struct intel_display *display = to_intel_display(crtc_state); + struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc); struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode; + u64 dividend; + u32 mode_rate_mhz; + u32 requested_rate_mhz = crtc->force_cmrr.numerator; + int rr_multiplier = 1, rr_divider = 1; - /* Avoid CMRR for now till we have VRR with fixed timings working */ - if (!intel_vrr_cmrr_possible(crtc_state) || true) - return false; - - actual_refresh_k = - drm_mode_vrefresh(adjusted_mode) * FIXED_POINT_PRECISION; - pixel_clock_per_line = - adjusted_mode->crtc_clock * 1000 / adjusted_mode->crtc_htotal; - calculated_refresh_k = - pixel_clock_per_line * FIXED_POINT_PRECISION / adjusted_mode->crtc_vtotal; - - if ((actual_refresh_k - calculated_refresh_k) < CMRR_PRECISION_TOLERANCE) - return false; - - return true; -} - -static unsigned int -cmrr_get_vtotal(struct intel_crtc_state *crtc_state, bool video_mode_required) -{ - int multiplier_m = 1, multiplier_n = 1, vtotal, desired_refresh_rate; - u64 adjusted_pixel_rate; - struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode; + if (!intel_vrr_cmrr_possible(crtc_state)) + return; - desired_refresh_rate = drm_mode_vrefresh(adjusted_mode); + /* No CMRR ratio configured through debugfs */ + if (!requested_rate_mhz) + return; - if (video_mode_required) { - multiplier_m = 1001; - multiplier_n = 1000; + /* Requested rate must match the mode's nominal (integer) refresh rate */ + if (DIV_ROUND_CLOSEST(requested_rate_mhz, 1000) != + drm_mode_vrefresh(adjusted_mode)) { + drm_dbg_kms(display->drm, + "[CRTC:%d:%s] CMRR requested %u.%03u Hz doesn't match mode %d Hz\n", + crtc->base.base.id, crtc->base.name, + requested_rate_mhz / 1000, requested_rate_mhz % 1000, + drm_mode_vrefresh(adjusted_mode)); + return; } - crtc_state->vrr.cmrr.cmrr_n = mul_u32_u32(desired_refresh_rate * adjusted_mode->crtc_htotal, - multiplier_n); - vtotal = DIV_ROUND_UP_ULL(mul_u32_u32(adjusted_mode->crtc_clock * 1000, multiplier_n), - crtc_state->vrr.cmrr.cmrr_n); - adjusted_pixel_rate = mul_u32_u32(adjusted_mode->crtc_clock * 1000, multiplier_m); - crtc_state->vrr.cmrr.cmrr_m = do_div(adjusted_pixel_rate, crtc_state->vrr.cmrr.cmrr_n); - - return vtotal; -} + /* Actual rate produced by the current timings, in milli-Hz */ + mode_rate_mhz = + DIV_ROUND_CLOSEST_ULL((u64)adjusted_mode->crtc_clock * 1000 * 1000, + adjusted_mode->crtc_vtotal * + adjusted_mode->crtc_htotal); -static -void intel_vrr_compute_cmrr_timings(struct intel_crtc_state *crtc_state) -{ /* - * TODO: Compute precise target refresh rate to determine - * if video_mode_required should be true. Currently set to - * false due to uncertainty about the precise target - * refresh Rate. + * A 1:1 ratio (denominator == 1000) means no video timing is required + * Any other ratio (e.g. 1000/1001) requires the video timing. */ - crtc_state->vrr.vmax = cmrr_get_vtotal(crtc_state, false); - crtc_state->vrr.vmin = crtc_state->vrr.vmax; - crtc_state->vrr.flipline = crtc_state->vrr.vmin; + if (crtc->force_cmrr.denominator == 1000) { + rr_multiplier = 1; + rr_divider = 1; + + /* Mode already hits the exact rate -> CMRR not needed */ + if (DIV_ROUND_CLOSEST(mode_rate_mhz, 10) == + DIV_ROUND_CLOSEST(requested_rate_mhz, 10)) { + drm_dbg_kms(display->drm, + "[CRTC:%d:%s] %u.%03u Hz can be driven without CMRR\n", + crtc->base.base.id, crtc->base.name, + requested_rate_mhz / 1000, requested_rate_mhz % 1000); + return; + } + } else { + rr_multiplier = 1000; + rr_divider = 1001; + } - crtc_state->vrr.cmrr.enable = true; - crtc_state->mode_flags |= I915_MODE_FLAG_VRR; + /* + * Let pixel_clock_hz = adjusted_mode->crtc_clock * 1000. + * + * cmrr_n = (requested_rate_mhz x htotal x rr_multiplier) / 1000 + * cmrr_m = (pixel_clock_hz x rr_divider) % cmrr_n + * + * where requested_rate_mhz is the requested refresh rate in milli-Hz + * and rr_multiplier/rr_divider = 1000/1001 when the video timing + * is required, else 1/1. The integer vtotal term is tracked in SW + * (it is the programmed mode vtotal) while the fractional part + * represented by cmrr_m/cmrr_n is tracked in HW. + * + * TODO: Using the actual desired rate for cmrr_n in video + * mode produces more aggressive vtotal dithering than + * expected; revisit once the Bspec algorithm is clarified. + */ + crtc_state->vrr.cmrr.cmrr_n = + div64_u64((u64)requested_rate_mhz * + adjusted_mode->crtc_htotal * rr_multiplier, 1000); + dividend = (u64)adjusted_mode->crtc_clock * rr_divider * 1000; + adjusted_mode->crtc_vtotal = div64_u64_rem(dividend, + crtc_state->vrr.cmrr.cmrr_n, + &crtc_state->vrr.cmrr.cmrr_m); } static @@ -435,8 +450,6 @@ intel_vrr_compute_config(struct intel_crtc_state *crtc_state, struct intel_display *display = to_intel_display(crtc_state); struct intel_connector *connector = to_intel_connector(conn_state->connector); - struct intel_dp *intel_dp = intel_attached_dp(connector); - bool is_edp = intel_dp_is_edp(intel_dp); struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode; int vmin, vmax; @@ -470,12 +483,17 @@ intel_vrr_compute_config(struct intel_crtc_state *crtc_state, vmax = vmin; } - if (crtc_state->uapi.vrr_enabled && vmin < vmax) + if (crtc_state->uapi.vrr_enabled && vmin < vmax) { intel_vrr_compute_vrr_timings(crtc_state, vmin, vmax); - else if (is_cmrr_frac_required(crtc_state) && is_edp) - intel_vrr_compute_cmrr_timings(crtc_state); - else + } else { + /* + * CMRR is a fixed average Vtotal mode and is only computed on + * the fixed refresh rate path. It is generic across transcoders + * and gated on platform support and a valid debugfs ratio. + */ + intel_vrr_cmrr_compute_config(crtc_state); intel_vrr_compute_fixed_rr_timings(crtc_state); + } if (HAS_AS_SDP(display)) { crtc_state->vrr.vsync_start = @@ -1142,11 +1160,6 @@ void intel_vrr_get_config(struct intel_crtc_state *crtc_state) intel_vrr_get_dc_balance_config(crtc_state); - /* - * #TODO: For Both VRR and CMRR the flag I915_MODE_FLAG_VRR is set for mode_flags. - * Since CMRR is currently disabled, set this flag for VRR for now. - * Need to keep this in mind while re-enabling CMRR. - */ if (crtc_state->vrr.enable) crtc_state->mode_flags |= I915_MODE_FLAG_VRR; -- 2.48.1