Re:Re: [PATCH 13/14] drm/bridge: synopsys: Add DW HDMI QP TX controller driver

Andy Yan
2024-06-14T06:57:38Z

Hi Neil，

At 2024-06-05 19:48:09, "Neil Armstrong" <neil.armstrong@linaro.org> 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!

Based on the previous discussion， the DW HDMI QP drivers will be implemented like this：

Core bridge library：
drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
Rockchip platform specific glue：
drivers/gpu/drm/rockchip/dw_hdmi_qp-rockchip.c

As a new bridge driver should only support DRM_BRIDGE_ATTACH_NO_CONNECTOR,
Is it acceptable if we implement the connector at the rockchip glue dw_hdmi_qp-rockchip.c ？

Our current combination is a bit complex：
The display controller driver is drivers/gpu/drm/rockchip/rockchip_drm_vop2.c ，which shared
by rk3568， rk3588 and some upcoming soc like rk3528/rk3562.

For rk3588， we have totally new HDMI、DP、DSI2 IP， they need brand new bridge driver that
should only support DRM_BRIDGE_ATTACH_NO_CONNECTOR， and there is also an eDP on rk3588
use analogix_dp_core.c that create connector by analogix_dp bridge。

For rk3568， the HDMI/eDP/DSI IP are based on old IP， the corresponding drivers are dw-hdmi，analogix_dp
and dw-mipi-dsi, they both create drm connector by it's bridge driver. And rk3528/rk3562 are like this too。

So if we can create drm_connector at glue side (such as dw_hdmi_qp-rockchip.c), let the interface driver decide
if it should create drm_connector or not will make the vop2 driver simpler。

>
>Neil
>
>>
>> Cristian