by Heiko Stuebner

[permalink] [raw]

Subject: Re: [PATCH 00/14] Add initial support for the Rockchip RK3588 HDMI TX Controller

Am Montag, 3. Juni 2024, 14:14:17 CEST schrieb Andy Yan:
> Hi Neil:
>
> On 6/3/24 16:55, Neil Armstrong wrote:
> > Hi Christian,
> >
> > On 01/06/2024 15:12, Cristian Ciocaltea wrote:
> >> The RK3588 SoC family integrates a Quad-Pixel (QP) variant of the
> >> Synopsys DesignWare HDMI TX controller used in the previous SoCs.
> >>
> >> It is HDMI 2.1 compliant and supports the following features, among
> >> others:
> >>
> > .
> >
> > ..
> >
> >> * SCDC I2C DDC access
> >> * TMDS Scrambler enabling 2160p@60Hz with RGB/YCbCr4:4:4
> >> * YCbCr4:2:0 enabling 2160p@60Hz at lower HDMI link speeds
> >> * Multi-stream audio
> >> * Enhanced Audio Return Channel (EARC)
> > -> Those features were already supported by the HDMI 2.0a compliant HW, just
> > list the _new_ features for HDMI 2.1
> >
> > I did a quick review of your patchset and I don't understand why you need
> > to add a separate dw-hdmi-qp.c since you only need simple variants of the I2C
> > bus, infoframe and bridge setup.
> >
> > Can you elaborate further ? isn't this Quad-Pixel (QP) TX controller version
> > detectable at runtime ?
> >
> > I would prefer to keep a single dw-hdmi driver if possible.
>
>
>
> The QP HDMI controller is a completely different variant with totally different
> registers layout, see PATCH 13/14.
> I think make it a separate driver will be easier for development and maintenance.

I'm with Andy here. Trying to navigate a driver for two IP blocks really
sounds taxing especially when both are so different.

Synopsis also created a new dsi controller for the DSI2 standard, with
a vastly different registers layout.

I guess at some point there is time to say this really is a new IP ;-) .

Though while on that thought, I don't fully understand why both a compiled
under the dw_hdmi kconfig symbol. People going for a minimal kernel might
want one or the other, but not both for their specific board.

Heiko

2024-06-03 16:22:26

2024-06-14 08:40:43

by Neil Armstrong

[permalink] [raw]

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

On 14/06/2024 08:56, Andy Yan wrote:
>
>
>
>
>
>
>
> Hi Neil，
>
> At 2024-06-05 19:48:09, "Neil Armstrong" <[email protected]> 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。

I think you should start migration to drm_bridge_connector instead of hacking dw_hdmi_qp-rockchip.c into
fitting into DRM_BRIDGE_ATTACH_NO_CONNECTOR.

You'll add technical dept, and the migration will be even harder afterwards.

But in any case, bridge/synopsys/dw-hdmi-qp.c and rockchip/dw_hdmi_qp-rockchip.c should be send
in two separate patchsets, so how rockchip DRM_BRIDGE_ATTACH_NO_CONNECTOR is a different story.

Neil

>
>
>
>
>
>>
>> Neil
>>
>>>
>>> Cristian