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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 94DADC433F5 for ; Tue, 4 Oct 2022 00:27:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229861AbiJDA1E (ORCPT ); Mon, 3 Oct 2022 20:27:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58858 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229639AbiJDA06 (ORCPT ); Mon, 3 Oct 2022 20:26:58 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DCEB81B9F4; Mon, 3 Oct 2022 17:26:57 -0700 (PDT) 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 ams.source.kernel.org (Postfix) with ESMTPS id 9C0EEB80DC3; Tue, 4 Oct 2022 00:26:56 +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 Cc: phone-devel@vger.kernel.org, Rob Clark , Dmitry Baryshkov , Vinod Koul , ~postmarketos/upstreaming@lists.sr.ht, AngeloGioacchino Del Regno , Konrad Dybcio , Martin Botka , Jami Kettunen , David Airlie , Daniel Vetter , Abhinav Kumar , Sean Paul , Thomas Zimmermann , Javier Martinez Canillas , Alex Deucher , Douglas Anderson , Vladimir Lypak , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org, Marek Vasut 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> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 >