linux-kernel - Re: [Letux-kernel] [PATCH v16 1/4] drm/bridge: dw-hdmi: introduce dw_hdmi_enable

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Date:   Thu, 3 Mar 2022 17:43:05 +0100
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Neil Armstrong <narmstrong@...libre.com>
Cc:     Paul Boddie <paul@...die.org.uk>, Daniel Vetter <daniel@...ll.ch>,
        Maxime Ripard <maxime@...no.tech>,
        Jonas Karlman <jonas@...boo.se>,
        David Airlie <airlied@...ux.ie>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-mips <linux-mips@...r.kernel.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Paul Cercueil <paul@...pouillou.net>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Robert Foss <robert.foss@...aro.org>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>
Subject: Re: [Letux-kernel] [PATCH v16 1/4] drm/bridge: dw-hdmi: introduce
 dw_hdmi_enable_poll()

Hi Neil,

> Am 03.03.2022 um 17:30 schrieb H. Nikolaus Schaller <hns@...delico.com>:
> 
> Hi Neil,
> 
>> Am 03.03.2022 um 17:23 schrieb Neil Armstrong <narmstrong@...libre.com>:
>> 
>> Hi,
>> 
>> On 26/02/2022 18:12, H. Nikolaus Schaller wrote:
>>> so that specialization drivers like ingenic-dw-hdmi can enable polling.
>>> Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>
>>> ---
>>> drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 9 +++++++++
>>> include/drm/bridge/dw_hdmi.h              | 1 +
>>> 2 files changed, 10 insertions(+)
>>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>>> index 4befc104d2200..43e375da131e8 100644
>>> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>>> @@ -3217,6 +3217,15 @@ static int dw_hdmi_parse_dt(struct dw_hdmi *hdmi)
>>> 	return 0;
>>> }
>>> +void dw_hdmi_enable_poll(struct dw_hdmi *hdmi, bool enable)
>>> +{
>>> +	if (hdmi->bridge.dev)
>>> +		hdmi->bridge.dev->mode_config.poll_enabled = enable;
>>> +	else
>>> +		dev_warn(hdmi->dev, "no hdmi->bridge.dev");
>>> +}
>>> +EXPORT_SYMBOL_GPL(dw_hdmi_enable_poll);
>>> +
>>> struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,
>>> 			      const struct dw_hdmi_plat_data *plat_data)
>>> {
>>> diff --git a/include/drm/bridge/dw_hdmi.h b/include/drm/bridge/dw_hdmi.h
>>> index 2a1f85f9a8a3f..963960794b40e 100644
>>> --- a/include/drm/bridge/dw_hdmi.h
>>> +++ b/include/drm/bridge/dw_hdmi.h
>>> @@ -196,5 +196,6 @@ enum drm_connector_status dw_hdmi_phy_read_hpd(struct dw_hdmi *hdmi,
>>> void dw_hdmi_phy_update_hpd(struct dw_hdmi *hdmi, void *data,
>>> 			    bool force, bool disabled, bool rxsense);
>>> void dw_hdmi_phy_setup_hpd(struct dw_hdmi *hdmi, void *data);
>>> +void dw_hdmi_enable_poll(struct dw_hdmi *hdmi, bool enable);
>>>   #endif /* __IMX_HDMI_H__ */
>> 
>> As I understand, this is because the IRQ line of the dw-hdmi IP isn't connected right ? and you use the display-connector ddc gpio instead ?
> 
> Yes. The IRQ line is not connected on all boards as far as I can see.
> 
>> 
>> In this case I think the Ingenic DRM core should call drm_kms_helper_poll_init(drm) instead.
> 
> Ah, that is good. it seems to do "dw_hdmi_enable_poll()" in a more generic way.

Well, I looked through source code and it is defined as 

	void drm_kms_helper_poll_init(struct drm_device *dev)

But there is no direct pointer to some drm_device available.
Neither in dw-hdmi nor ingenic-dw-hdmi.

What should the parameter to drm_kms_helper_poll_init(drm) be?

From comparing code to be able to set mode_config.poll_enabled = enable it should be

	&hdmi->bridge.dev

but the struct dw_hdmi *hdmi is an opaque type for the ingenic-dw-hdmi driver.
So it can't access the hdmi-bridge directly.

What we can do is to make dw_hdmi_enable_poll() call drm_kms_helper_poll_init()
or drm_kms_helper_poll_fini().

BR and thanks,
Nikolaus