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[2001:14ba:a0db:1f00::8a5]) by smtp.gmail.com with ESMTPSA id l9-20020ac24309000000b004f3b520e0adsm329680lfh.107.2023.05.30.05.36.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 30 May 2023 05:36:05 -0700 (PDT) Message-ID: Date: Tue, 30 May 2023 15:36:04 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: RFC: DSI host capabilities (was: [PATCH RFC 03/10] drm/panel: Add LGD panel driver for Sony Xperia XZ3) Content-Language: en-GB To: AngeloGioacchino Del Regno , Neil Armstrong Cc: Marijn Suijten , Caleb Connolly , Jessica Zhang , Sam Ravnborg , David Airlie , Daniel Vetter , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Andy Gross , Bjorn Andersson , ~postmarketos/upstreaming@lists.sr.ht, AngeloGioacchino Del Regno , Konrad Dybcio , Martin Botka , Jami Kettunen , "open list:DRM DRIVER FOR MSM ADRENO GPU" , open list , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , "open list:DRM DRIVER FOR MSM ADRENO GPU" , Abhinav Kumar , Kuogee Hsieh , freedreno References: <20230521-drm-panels-sony-v1-0-541c341d6bee@somainline.org> <20230521-drm-panels-sony-v1-3-541c341d6bee@somainline.org> <617c8f8a-1fc7-c6a0-eaa5-ce75ff2adc1b@linaro.org> <739a8bd9-9ff0-5072-fdae-b64efdf86842@collabora.com> From: Dmitry Baryshkov In-Reply-To: <739a8bd9-9ff0-5072-fdae-b64efdf86842@collabora.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On 30/05/2023 15:15, AngeloGioacchino Del Regno wrote: > Il 30/05/23 13:44, Dmitry Baryshkov ha scritto: >> On Tue, 30 May 2023 at 10:24, Neil Armstrong >> wrote: >>> >>> Hi Marijn, Dmitry, Caleb, Jessica, >>> >>> On 29/05/2023 23:11, Marijn Suijten wrote: >>>> On 2023-05-22 04:16:20, Dmitry Baryshkov wrote: >>>> >>>>>> +   if (ctx->dsi->dsc) { >>>>> >>>>> dsi->dsc is always set, thus this condition can be dropped. >>>> >>>> I want to leave room for possibly running the panel without DSC (at a >>>> lower resolution/refresh rate, or at higher power consumption if there >>>> is enough BW) by not assigning the pointer, if we get access to panel >>>> documentation: probably one of the magic commands sent in this driver >>>> controls it but we don't know which. >>> >>> I'd like to investigate if DSC should perhaps only be enabled if we >>> run non certain platforms/socs ? >>> >>> I mean, we don't know if the controller supports DSC and those >>> particular >>> DSC parameters so we should probably start adding something like : >>> >>> static drm_dsc_config dsc_params_qcom = {} >>> >>> static const struct of_device_id panel_of_dsc_params[] = { >>>          { .compatible = "qcom,sm8150", , .data = &dsc_params_qcom }, >>>          { .compatible = "qcom,sm8250", , .data = &dsc_params_qcom }, >>>          { .compatible = "qcom,sm8350", , .data = &dsc_params_qcom }, >>>          { .compatible = "qcom,sm8450", , .data = &dsc_params_qcom }, >>> }; >> >> I think this would damage the reusability of the drivers. The panel >> driver does not actually care if the SoC is SM8350, sunxi-something or >> RCar. >> Instead it cares about host capabilities. >> >> I think instead we should extend mipi_dsi_host: >> >> #define MIPI_DSI_HOST_MODE_VIDEO BIT(0) >> #define MIPI_DSI_HOST_MODE_CMD  BIT(1) >> #define MIPI_DSI_HOST_VIDEO_SUPPORTS_COMMANDS BIT(2) >> // FIXME: do we need to provide additional caps here ? >> >> #define MIPI_DSI_DSC_1_1 BIT(0) >> #define MIPI_DSI_DSC_1_2 BIT(1) >> #define MIPI_DSI_DSC_NATIVE_422 BIT(2) >> #define MIPI_DSI_DSC_NATIVE_420 BIT(3) >> #define MIPI_DSI_DSC_FRAC_BPP BIT(4) >> // etc. >> >> struct mipi_dsi_host { >>   // new fields only >>    unsigned long mode_flags; >>    unsigned long dsc_flags; >> }; >> >> Then the panel driver can adapt itself to the host capabilities and >> (possibly) select one of the internally supported DSC profiles. >> > > I completely agree about extending mipi_dsi_host, other SoCs could reuse > that and > support for DSC panels would become a lot cleaner. Sounds good. I will wait for one or two more days (to get the possible feedback on fields/flags/etc) and post an RFC patch to dri-devel. > > For example, on MediaTek DRM there's some support for DSC, more or less > the same > for SPRD DRM and some DSI bridge drivers... having a clean > infrastructure would > definitely help. > > I'm sad I cannot offer testing in that case because despite being sure > that there > are MTK smartphones around with DSI panels using DSC, I have none... and > all of the > Chromebooks are not using DSC anyway (but using DisplayPort compression, > which is > obviously an entirely different beast). > >>> >>> ... >>> static int sony_akatsuki_lgd_probe(struct mipi_dsi_device *dsi) >>> ... >>>          const struct of_device_id *match; >>> >>> ... >>>          match = of_match_node(panel_of_dsc_params, of_root); >>>          if (match && match->data) { >>>                  dsi->dsc = devm_kzalloc(&dsi->dev, sizeof(*dsc), >>> GFP_KERNEL); >>>                  memcpy(dsi->dsc, match->data, sizeof(*dsc)); >>>          } else { >>>                  dev_warn(&dsi->dev, "DSI controller is not marked as >>> supporting DSC\n"); >>>          } >>> ... >>> } >>> >>> and probably bail out if it's a DSC only panel. >>> > > Usually DDICs support both DSC and non-DSC modes, depending on the initial > programming (read: init commands)... but the usual issue is that many DDICs > are not publicly documented for reasons, so yes, bailing out if DSC is not > supported would be the only option, and would be fine at this point. > > Cheers, > Angelo > >>> We could alternatively match on the DSI controller's dsi->host->dev >>> instead of the SoC root compatible. >>> >>> Neil >> > -- With best wishes Dmitry