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 C27A6C433F5 for ; Thu, 14 Apr 2022 17:59:51 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 3B4ED10E1B8; Thu, 14 Apr 2022 17:59:51 +0000 (UTC) Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by gabe.freedesktop.org (Postfix) with ESMTPS id 3E63210E1B8 for ; Thu, 14 Apr 2022 17:59:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1649959190; x=1681495190; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=qOc9X3y/UXzAKitx1Gq+jrbkRw7OKaqLzpcuXay/gS8=; b=TRh9vLt0xklx1sIhDEYZrW2smlOaEhFQ9DMmmAhcm1qMDifsGl7piY/Z Qu0eIYlwDiujKEgEsck3fb4syZmCtWJmt0R5qOxJg9BUCGfS/es9L4FfM FU99wVlRA1hnSGRr6fXQwHDoN/UUe50jzsklUDjAdCR7i8DbZo+ORW2mS zv5GxTWNxU/Uhfi3sizuhC+AbDJ7pVjt65UqTTmJHJ1CtfZK9V24XOPhI 0/Z5FsUtfyM5B57AneIppoKWMWBDIUN30Rh6063fmpO6z0m5Vn/Cdcxae nOgRNQsBX8YR0IwHVu87EZyEVM6HaQR2L6RfKa1dq1kIym+JZtVj47ABa w==; X-IronPort-AV: E=McAfee;i="6400,9594,10317"; a="349431272" X-IronPort-AV: E=Sophos;i="5.90,260,1643702400"; d="scan'208";a="349431272" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Apr 2022 10:59:49 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.90,260,1643702400"; d="scan'208";a="527008002" Received: from stinkpipe.fi.intel.com (HELO stinkbox) ([10.237.72.51]) by orsmga002.jf.intel.com with SMTP; 14 Apr 2022 10:59:47 -0700 Received: by stinkbox (sSMTP sendmail emulation); Thu, 14 Apr 2022 20:59:46 +0300 Date: Thu, 14 Apr 2022 20:59:46 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Vinod Govindapillai Message-ID: References: <20220406174311.82104-1-vinod.govindapillai@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220406174311.82104-1-vinod.govindapillai@intel.com> X-Patchwork-Hint: comment Subject: Re: [Intel-gfx] [PATCH v3] drm/i915: program wm blocks to at least blocks required per line 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: intel-gfx@lists.freedesktop.org Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Wed, Apr 06, 2022 at 08:43:11PM +0300, Vinod Govindapillai wrote: > In configurations with single DRAM channel, for usecases like > 4K 60 Hz, FIFO underruns are observed quite frequently. Looks > like the wm0 watermark values need to bumped up because the wm0 > memory latency calculations are probably not taking the DRAM > channel's impact into account. > > As per the Bspec 49325, if the ddb allocation can hold at least > one plane_blocks_per_line we should have selected method2. > Assuming that modern HW versions have enough dbuf to hold > at least one line, set the wm blocks to equivalent to blocks > per line. > > V2: styling and comments changes (Ville) > V3: Updated the reviewed-by tag > > cc: Ville Syrjälä > cc: Stanislav Lisovskiy > Normally people put all the tags in one block, ie. no extra newlines like this. Also 'Cc:' is the normal form for these. I was expecting to see gitlab issue links here. Maybe not Closes: since this is not the final form I guess. But could slap them on here as References:. > Signed-off-by: Vinod Govindapillai > Reviewed-by: Stanislav Lisovskiy > --- > drivers/gpu/drm/i915/intel_pm.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c > index 8824f269e5f5..d284ec8aff21 100644 > --- a/drivers/gpu/drm/i915/intel_pm.c > +++ b/drivers/gpu/drm/i915/intel_pm.c > @@ -5475,6 +5475,25 @@ static void skl_compute_plane_wm(const struct intel_crtc_state *crtc_state, > } > > blocks = fixed16_to_u32_round_up(selected_result) + 1; > + /* > + * Lets have blocks at minimum equivalent to plane_blocks_per_line > + * as there will be at minimum one line for lines configuration. This > + * is a work around for FIFO underruns observed with resolutions like > + * 4k 60 Hz in single channel DRAM configurations. > + * > + * As per the Bspec 49325, if the ddb allocation can hold at least > + * one plane_blocks_per_line, we should have selected method2 in > + * the above logic. Assuming that modern versions have enough dbuf > + * and method2 guarantees blocks equivalent to at least 1 line, > + * select the blocks as plane_blocks_per_line. > + * > + * TODO: Revisit the logic when we have better understanding on DRAM > + * channels' impact on the level 0 memory latency and the relevant > + * wm calculations. > + */ > + if (skl_wm_has_lines(dev_priv, level)) > + blocks = max_t(u32, blocks, > + fixed16_to_u32_round_up(wp->plane_blocks_per_line)); A simple max() should do since the types are the same. > lines = div_round_up_fixed16(selected_result, > wp->plane_blocks_per_line); > > -- > 2.25.1 -- Ville Syrjälä Intel