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[135.19.110.125]) by smtp.gmail.com with ESMTPSA id w19-20020ac843d3000000b0041991642c62sm4493571qtn.73.2023.11.16.10.46.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Nov 2023 10:46:44 -0800 (PST) Subject: Re: [PATCH v2 4/6] drm/msm/dsi: add a comment to explain pkt_per_line encoding To: Dmitry Baryshkov Cc: freedreno@lists.freedesktop.org, Rob Clark , Abhinav Kumar , Sean Paul , Marijn Suijten , David Airlie , Daniel Vetter , Jessica Zhang , Konrad Dybcio , Jiasheng Jiang , "open list:DRM DRIVER FOR MSM ADRENO GPU" , "open list:DRM DRIVER FOR MSM ADRENO GPU" , open list References: <20231114225857.19702-1-jonathan@marek.ca> <20231114225857.19702-5-jonathan@marek.ca> From: Jonathan Marek Message-ID: Date: Thu, 16 Nov 2023 13:45:47 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/15/23 2:38 AM, Dmitry Baryshkov wrote: > On Wed, 15 Nov 2023 at 01:00, Jonathan Marek wrote: >> >> Make it clear why the pkt_per_line value is being "divided by 2". >> >> Signed-off-by: Jonathan Marek >> --- >> drivers/gpu/drm/msm/dsi/dsi_host.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c >> index 66f198e21a7e..842765063b1b 100644 >> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c >> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c >> @@ -877,6 +877,8 @@ static void dsi_update_dsc_timing(struct msm_dsi_host *msm_host, bool is_cmd_mod >> /* DSI_VIDEO_COMPRESSION_MODE & DSI_COMMAND_COMPRESSION_MODE >> * registers have similar offsets, so for below common code use >> * DSI_VIDEO_COMPRESSION_MODE_XXXX for setting bits >> + * >> + * pkt_per_line is log2 encoded, >>1 works for supported values (1,2,4) >> */ >> reg |= DSI_VIDEO_COMPRESSION_MODE_CTRL_PKT_PER_LINE(pkt_per_line >> 1); > > Should we switch to ffs() or fls() instead? > Just a ffs() on its own can be confusing as well (without the information that only powers of two are possible), I think like this is better. >> reg |= DSI_VIDEO_COMPRESSION_MODE_CTRL_EOL_BYTE_NUM(eol_byte_num); >> -- >> 2.26.1 >> > >