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 8A90BC433F5 for ; Tue, 4 Oct 2022 00:27:00 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 0BBC810E520; Tue, 4 Oct 2022 00:26:59 +0000 (UTC) Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by gabe.freedesktop.org (Postfix) with ESMTPS id 97D8510E520; Tue, 4 Oct 2022 00:26:56 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id DE30461230; Tue, 4 Oct 2022 00:26:55 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C7D22C433D7; Tue, 4 Oct 2022 00:26:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1664843215; bh=OA9gALTKKnHQ120A5UTTlN4CPGY9ult7j6PDay+Yy1M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WvlPoU8Qd1mJV9iVXVfw9hRnqYx5Er1VAytV/1aNisZe+s16mCe1PL2MzcnVKRXxT /MyXryezYGWaYGRXh+IRNOHf2aN5Al6WotSokibUKc2Zn6daKn6/LaLuvzDKtjuyVe HRweKcWOi85Mw9y8Uh3V0VTW+Tv1vT7gsu8YkBf9CbbqXcI69TsqR5/Z+/DDv4RRDV lJE61qV4IDqCf3xjFzRBq9Ihlt3332sGv/ozv12x98CnZiYQEt2n0Rz7Xv7tNdYYU8 mQYe2KbEdYzpWFkUpNrdrZRrNiwSqFOBkzkQTlZeQpFAE2hfGpmYzW6ZHgP8P7UAPE yOX8EVzlxXYEA== Date: Mon, 3 Oct 2022 19:26:50 -0500 From: Bjorn Andersson To: Marijn Suijten Subject: Re: [PATCH 1/5] drm/msm/dsi: Remove useless math in DSC calculation Message-ID: <20221004002650.joqwhmvzql55ospz@baldur> References: <20221001190807.358691-1-marijn.suijten@somainline.org> <20221001190807.358691-2-marijn.suijten@somainline.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221001190807.358691-2-marijn.suijten@somainline.org> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: David Airlie , Konrad Dybcio , dri-devel@lists.freedesktop.org, Javier Martinez Canillas , AngeloGioacchino Del Regno , phone-devel@vger.kernel.org, Marek Vasut , linux-arm-msm@vger.kernel.org, Abhinav Kumar , Dmitry Baryshkov , Martin Botka , ~postmarketos/upstreaming@lists.sr.ht, Sean Paul , Jami Kettunen , Vladimir Lypak , Douglas Anderson , linux-kernel@vger.kernel.org, Vinod Koul , Thomas Zimmermann , Alex Deucher , freedreno@lists.freedesktop.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Sat, Oct 01, 2022 at 09:08:03PM +0200, Marijn Suijten wrote: > Multiplying a value by 2 and adding 1 to it always results in a value > that is uneven, and that 1 gets truncated immediately when performing > integer division by 2 again. There is no "rounding" possible here. > > Fixes: b9080324d6ca ("drm/msm/dsi: add support for dsc data") > Signed-off-by: Marijn Suijten Reviewed-by: Bjorn Andersson > --- > drivers/gpu/drm/msm/dsi/dsi_host.c | 7 +------ > 1 file changed, 1 insertion(+), 6 deletions(-) > > diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c > index 8e4bc586c262..e05bae647431 100644 > --- a/drivers/gpu/drm/msm/dsi/dsi_host.c > +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c > @@ -1864,12 +1864,7 @@ static int dsi_populate_dsc_params(struct drm_dsc_config *dsc) > data = 2048 * (dsc->rc_model_size - dsc->initial_offset + num_extra_mux_bits); > dsc->slice_bpg_offset = DIV_ROUND_UP(data, groups_total); > > - /* bpp * 16 + 0.5 */ > - data = dsc->bits_per_pixel * 16; > - data *= 2; > - data++; > - data /= 2; > - target_bpp_x16 = data; > + target_bpp_x16 = dsc->bits_per_pixel * 16; > > data = (dsc->initial_xmit_delay * target_bpp_x16) / 16; > final_value = dsc->rc_model_size - data + num_extra_mux_bits; > -- > 2.37.3 >