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Wed, 5 Jun 2024 13:57:37 +0000 (UTC) Message-ID: <3fcef87b-6173-45fd-a7fc-f5e9d2541337@collabora.com> Date: Wed, 5 Jun 2024 16:57:37 +0300 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 13/14] drm/bridge: synopsys: Add DW HDMI QP TX controller driver To: neil.armstrong@linaro.org, Sam Ravnborg Cc: Andrzej Hajda , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Sandy Huang , =?UTF-8?Q?Heiko_St=C3=BCbner?= , Andy Yan , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Mark Yao , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, devicetree@vger.kernel.org, kernel@collabora.com, Alexandre ARNOUD , Luis de Arquer , Algea Cao References: <20240601-b4-rk3588-bridge-upstream-v1-0-f6203753232b@collabora.com> <20240601-b4-rk3588-bridge-upstream-v1-13-f6203753232b@collabora.com> <20240601143226.GA2003970@ravnborg.org> <59519381-2729-4839-9882-65a981a0c551@collabora.com> <20240604204110.GA84949@ravnborg.org> <304b4602-8722-4ed0-a555-8dada573ee79@collabora.com> <5dc16b34-d638-4fab-84e1-cb7db08ad80e@linaro.org> From: Cristian Ciocaltea Content-Language: en-US In-Reply-To: <5dc16b34-d638-4fab-84e1-cb7db08ad80e@linaro.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 6/5/24 2:48 PM, Neil Armstrong wrote: > On 05/06/2024 12:11, Cristian Ciocaltea wrote: >> On 6/5/24 12:34 AM, Cristian Ciocaltea wrote: >>> On 6/4/24 11:41 PM, Sam Ravnborg wrote: >>>> Hi Cristian. >>>> >>>> On Tue, Jun 04, 2024 at 10:32:04PM +0300, Cristian Ciocaltea wrote: >>>>> Hi Sam, >>>>> >>>>> On 6/1/24 5:32 PM, Sam Ravnborg wrote: >>>>>> Hi Cristian, >>>>>> >>>>>> a few drive-by comments below. >>>>>> >>>>>>     Sam >>>>>> >>>>>> >>>>>>> + >>>>>>> +static const struct drm_connector_funcs >>>>>>> dw_hdmi_qp_connector_funcs = { >>>>>>> +    .fill_modes = drm_helper_probe_single_connector_modes, >>>>>>> +    .detect = dw_hdmi_connector_detect, >>>>>>> +    .destroy = drm_connector_cleanup, >>>>>>> +    .force = dw_hdmi_qp_connector_force, >>>>>>> +    .reset = drm_atomic_helper_connector_reset, >>>>>>> +    .atomic_duplicate_state = >>>>>>> drm_atomic_helper_connector_duplicate_state, >>>>>>> +    .atomic_destroy_state = >>>>>>> drm_atomic_helper_connector_destroy_state, >>>>>>> +}; >>>>>>> + >>>>>>> +static int dw_hdmi_qp_bridge_attach(struct drm_bridge *bridge, >>>>>>> +                    enum drm_bridge_attach_flags flags) >>>>>>> +{ >>>>>>> +    struct dw_hdmi *hdmi = bridge->driver_private; >>>>>>> + >>>>>>> +    if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) >>>>>>> +        return drm_bridge_attach(bridge->encoder, >>>>>>> hdmi->next_bridge, >>>>>>> +                     bridge, flags); >>>>>>> + >>>>>>> +    return dw_hdmi_connector_create(hdmi, >>>>>>> &dw_hdmi_qp_connector_funcs); >>>>>>> +} >>>>>> >>>>>> Are there any users left that requires the display driver to >>>>>> create the >>>>>> connector? >>>>>> In other words - could this driver fail if >>>>>> DRM_BRIDGE_ATTACH_NO_CONNECTOR >>>>>> is not passed and drop dw_hdmi_connector_create()? >>>>>> >>>>>> I did not try to verify this - just a naive question. >>>>> >>>>> I've just tested this and it doesn't work - dw_hdmi_connector_create() >>>>> is still needed. >>>> >>>> Hmm, seems the display driver or some other bridge driver fails to >>>> support "DRM_BRIDGE_ATTACH_NO_CONNECTOR". >>>> what other drivers are involved? >>> >>> Could it be related to the glue driver (updated in the next patch) which >>> is also responsible for setting up the encoder? >>> >>>> Note that my comments here should be seen as potential future >>>> improvements, and do not block the patch from being used. >>> >>> Thanks for the heads up! Will try to get back to this soon and >>> investigate. >>   IIUC, modern bridges should not create the connector but rely on >> display >> drivers to take care of, which in this case is the VOP2 driver. However, >> it also handles some of the older SoCs relying on the non-QP variant of >> DW HDMI IP. Hence the existing dw-hdmi driver would be also impacted in >> order to come up with a proper solution. >> >> A quick check shows there are several users of this IP: >> >> $ git grep -E '= dw_hdmi_(bind|probe)\(' >> drivers/gpu/drm/bridge/imx/imx8mp-hdmi-tx.c:    hdmi->dw_hdmi = >> dw_hdmi_probe(pdev, plat_data); >> drivers/gpu/drm/bridge/synopsys/dw-hdmi.c:      hdmi = >> dw_hdmi_probe(pdev, plat_data); >> drivers/gpu/drm/imx/ipuv3/dw_hdmi-imx.c:        hdmi->hdmi = >> dw_hdmi_probe(pdev, match->data); >> drivers/gpu/drm/ingenic/ingenic-dw-hdmi.c:      hdmi = >> dw_hdmi_probe(pdev, &ingenic_dw_hdmi_plat_data); >> drivers/gpu/drm/meson/meson_dw_hdmi.c:  meson_dw_hdmi->hdmi = >> dw_hdmi_probe(pdev, &meson_dw_hdmi->dw_plat_data); >> drivers/gpu/drm/renesas/rcar-du/rcar_dw_hdmi.c: hdmi = >> dw_hdmi_probe(pdev, &rcar_dw_hdmi_plat_data); >> drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c:            hdmi->hdmi = >> dw_hdmi_bind(pdev, encoder, plat_data); >> drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c:  hdmi->hdmi = >> dw_hdmi_bind(pdev, encoder, plat_data); >> >> I didn't check which display drivers would be involved, I'd guess there >> are quite a few of them as well. So it seems this ends up being a pretty >> complex task. > > If this would be a brand new driver, then it should only support > DRM_BRIDGE_ATTACH_NO_CONNECTOR, > so you should not create a connector from the driver. > > The fact dw-hdmi accepts an attach without the flag is for legacy purpose > since some DRM drivers haven't switched to > DRM_BRIDGE_ATTACH_NO_CONNECTOR yes, > but it's a requirement for new bridges so at some point you'll need to make > sure the rockchip glue and drm driver supports > DRM_BRIDGE_ATTACH_NO_CONNECTOR. > > This will greatly simplify the driver! Got it, thanks for the clarifications! Cristian