Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v2 2/3] drm/mediatek: Don't support hdmi connector
 creation
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     dri-devel@lists.freedesktop.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
        kernel@collabora.com, dafna3@gmail.com, chunkuang.hu@kernel.org,
        p.zabel@pengutronix.de, airlied@linux.ie, daniel@ffwll.ch,
        enric.balletbo@collabora.com
References: <20210329153632.17559-1-dafna.hirschfeld@collabora.com>
 <20210329153632.17559-3-dafna.hirschfeld@collabora.com>
 <YGJr+jopSvH4SdsL@pendragon.ideasonboard.com>
From:   Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Message-ID: <3ced4fcf-5ebb-5e34-dfcd-84545237b584@collabora.com>
Date:   Tue, 30 Mar 2021 11:44:12 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <YGJr+jopSvH4SdsL@pendragon.ideasonboard.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

Hi,

On 30.03.21 02:08, Laurent Pinchart wrote:
> Hi Dafna,
> 
> Thank you for the patch.
> 
> On Mon, Mar 29, 2021 at 05:36:31PM +0200, Dafna Hirschfeld wrote:
>> commit f01195148967 ("drm/mediatek: mtk_dpi: Create connector for bridges")
>> broke the display support for elm device since mtk_dpi calls
>> drm_bridge_attach with the flag DRM_BRIDGE_ATTACH_NO_CONNECTOR
>> while mtk_hdmi does not yet support this flag.
>>
>> Fix this by accepting DRM_BRIDGE_ATTACH_NO_CONNECTOR in bridge attachment.
>> Implement the drm_bridge_funcs .detect() and .get_edid() operations, and
>> call drm_bridge_hpd_notify() to report HPD. This provides the
>> necessary API to support disabling connector creation.
>>
>> This patch is inspired by a similar patch for bridge/synopsys/dw-hdmi.c:
>> commit ec971aaa6775 ("drm: bridge: dw-hdmi: Make connector creation optional")
>> But with the difference that in mtk-hdmi only the option of not creating
>> a connector is supported.
>>
>> Fixes: f01195148967 ("drm/mediatek: mtk_dpi: Create connector for bridges")
>> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
>> ---
>>   drivers/gpu/drm/mediatek/mtk_hdmi.c | 129 ++++++++++------------------
>>   1 file changed, 44 insertions(+), 85 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi.c b/drivers/gpu/drm/mediatek/mtk_hdmi.c
>> index f2c810b767ef..1eeb211b1536 100644
>> --- a/drivers/gpu/drm/mediatek/mtk_hdmi.c
>> +++ b/drivers/gpu/drm/mediatek/mtk_hdmi.c
>> @@ -186,11 +186,6 @@ static inline struct mtk_hdmi *hdmi_ctx_from_bridge(struct drm_bridge *b)
>>   	return container_of(b, struct mtk_hdmi, bridge);
>>   }
>>   
>> -static inline struct mtk_hdmi *hdmi_ctx_from_conn(struct drm_connector *c)
>> -{
>> -	return container_of(c, struct mtk_hdmi, conn);
>> -}
>> -
>>   static u32 mtk_hdmi_read(struct mtk_hdmi *hdmi, u32 offset)
>>   {
>>   	return readl(hdmi->regs + offset);
>> @@ -1201,48 +1196,30 @@ mtk_hdmi_update_plugged_status(struct mtk_hdmi *hdmi)
>>   	       connector_status_connected : connector_status_disconnected;
>>   }
>>   
>> -static enum drm_connector_status hdmi_conn_detect(struct drm_connector *conn,
>> -						  bool force)
>> -{
>> -	struct mtk_hdmi *hdmi = hdmi_ctx_from_conn(conn);
>> -	return mtk_hdmi_update_plugged_status(hdmi);
>> -}
>> -
>> -static void hdmi_conn_destroy(struct drm_connector *conn)
>> +static struct edid *mtk_hdmi_get_edid(struct mtk_hdmi *hdmi,
>> +				      struct drm_connector *connector)
>>   {
>> -	struct mtk_hdmi *hdmi = hdmi_ctx_from_conn(conn);
>> -
>> -	mtk_cec_set_hpd_event(hdmi->cec_dev, NULL, NULL);
>> -
>> -	drm_connector_cleanup(conn);
>> -}
>> -
>> -static int mtk_hdmi_conn_get_modes(struct drm_connector *conn)
>> -{
>> -	struct mtk_hdmi *hdmi = hdmi_ctx_from_conn(conn);
>>   	struct edid *edid;
>> -	int ret;
>>   
>>   	if (!hdmi->ddc_adpt)
>> -		return -ENODEV;
>> -
>> -	edid = drm_get_edid(conn, hdmi->ddc_adpt);
>> +		return NULL;
>> +	edid = drm_get_edid(connector, hdmi->ddc_adpt);
>>   	if (!edid)
>> -		return -ENODEV;
>> -
>> +		return NULL;
>>   	hdmi->dvi_mode = !drm_detect_monitor_audio(edid);
>> +	return edid;
>> +}
>>   
>> -	drm_connector_update_edid_property(conn, edid);
>> -
>> -	ret = drm_add_edid_modes(conn, edid);
>> -	kfree(edid);
>> -	return ret;
>> +static enum drm_connector_status mtk_hdmi_detect(struct mtk_hdmi *hdmi)
>> +{
>> +	return mtk_hdmi_update_plugged_status(hdmi);
>>   }
>>   
>> -static int mtk_hdmi_conn_mode_valid(struct drm_connector *conn,
>> -				    struct drm_display_mode *mode)
>> +static int mtk_hdmi_bridge_mode_valid(struct drm_bridge *bridge,
>> +				      const struct drm_display_info *info,
>> +				      const struct drm_display_mode *mode)
>>   {
>> -	struct mtk_hdmi *hdmi = hdmi_ctx_from_conn(conn);
>> +	struct mtk_hdmi *hdmi = hdmi_ctx_from_bridge(bridge);
>>   	struct drm_bridge *next_bridge;
>>   
>>   	dev_dbg(hdmi->dev, "xres=%d, yres=%d, refresh=%d, intl=%d clock=%d\n",
>> @@ -1267,74 +1244,50 @@ static int mtk_hdmi_conn_mode_valid(struct drm_connector *conn,
>>   	return drm_mode_validate_size(mode, 0x1fff, 0x1fff);
>>   }
>>   
>> -static struct drm_encoder *mtk_hdmi_conn_best_enc(struct drm_connector *conn)
>> -{
>> -	struct mtk_hdmi *hdmi = hdmi_ctx_from_conn(conn);
>> -
>> -	return hdmi->bridge.encoder;
>> -}
>> -
>> -static const struct drm_connector_funcs mtk_hdmi_connector_funcs = {
>> -	.detect = hdmi_conn_detect,
>> -	.fill_modes = drm_helper_probe_single_connector_modes,
>> -	.destroy = hdmi_conn_destroy,
>> -	.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 const struct drm_connector_helper_funcs
>> -		mtk_hdmi_connector_helper_funcs = {
>> -	.get_modes = mtk_hdmi_conn_get_modes,
>> -	.mode_valid = mtk_hdmi_conn_mode_valid,
>> -	.best_encoder = mtk_hdmi_conn_best_enc,
>> -};
>> -
>>   static void mtk_hdmi_hpd_event(bool hpd, struct device *dev)
>>   {
>>   	struct mtk_hdmi *hdmi = dev_get_drvdata(dev);
>>   
>> -	if (hdmi && hdmi->bridge.encoder && hdmi->bridge.encoder->dev)
>> +	if (hdmi && hdmi->bridge.encoder && hdmi->bridge.encoder->dev) {
>> +		static enum drm_connector_status status;
>> +
>> +		status = mtk_hdmi_detect(hdmi);
>>   		drm_helper_hpd_irq_event(hdmi->bridge.encoder->dev);
> 
> I think you can drop this, as drm_bridge_connector_hpd_cb() calls
> drm_kms_helper_hotplug_event().

I see that drm_kms_helper_hotplug_event is called from drm_bridge_connector_hpd_cb,
which is set as a birdge's 'hpd_cb' when calling drm_bridge_connector_enable_hpd,
but mkt_dpi does not call this funcion for the drm_bridge_connector.

I also wonder why bridges have both 'hpd_cb' and a function 'hpd_notify'.
It seems that both are called upon hot-plug event.
It is also confusing that the function drm_bridge_hpd_notify calls the 'hpd_cb'
and not the 'hpd_notfiy'. I can send a patch to change the name to 'drm_bridge_hpd_cb'

Thanks,
Dafna

> 
>> +		drm_bridge_hpd_notify(&hdmi->bridge, status);
>> +	}
>>   }
>>   
>>   /*
>>    * Bridge callbacks
>>    */
>>   
>> +static enum drm_connector_status mtk_hdmi_bridge_detect(struct drm_bridge *bridge)
>> +{
>> +	struct mtk_hdmi *hdmi = hdmi_ctx_from_bridge(bridge);
>> +
>> +	return mtk_hdmi_detect(hdmi);
>> +}
>> +
>> +static struct edid *mtk_hdmi_bridge_get_edid(struct drm_bridge *bridge,
>> +					     struct drm_connector *connector)
>> +{
>> +	struct mtk_hdmi *hdmi = hdmi_ctx_from_bridge(bridge);
>> +
>> +	return mtk_hdmi_get_edid(hdmi, connector);
> 
> As mtk_hdmi_get_edid() is only called here, you could inline it in this
> function. Up to you.
> 
>> +}
>> +
>>   static int mtk_hdmi_bridge_attach(struct drm_bridge *bridge,
>>   				  enum drm_bridge_attach_flags flags)
>>   {
>>   	struct mtk_hdmi *hdmi = hdmi_ctx_from_bridge(bridge);
>>   	int ret;
>>   
>> -	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
>> -		DRM_ERROR("Fix bridge driver to make connector optional!");
>> +	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)) {
>> +		DRM_ERROR("%s: The flag DRM_BRIDGE_ATTACH_NO_CONNECTOR must be supplied\n",
>> +			  __func__);
>>   		return -EINVAL;
>>   	}
>>   
>> -	ret = drm_connector_init_with_ddc(bridge->encoder->dev, &hdmi->conn,
>> -					  &mtk_hdmi_connector_funcs,
>> -					  DRM_MODE_CONNECTOR_HDMIA,
>> -					  hdmi->ddc_adpt);
>> -	if (ret) {
>> -		dev_err(hdmi->dev, "Failed to initialize connector: %d\n", ret);
>> -		return ret;
>> -	}
>> -	drm_connector_helper_add(&hdmi->conn, &mtk_hdmi_connector_helper_funcs);
>> -
>> -	hdmi->conn.polled = DRM_CONNECTOR_POLL_HPD;
>> -	hdmi->conn.interlace_allowed = true;
>> -	hdmi->conn.doublescan_allowed = false;
>> -
>> -	ret = drm_connector_attach_encoder(&hdmi->conn,
>> -						bridge->encoder);
>> -	if (ret) {
>> -		dev_err(hdmi->dev,
>> -			"Failed to attach connector to encoder: %d\n", ret);
>> -		return ret;
>> -	}
>> -
>>   	if (hdmi->next_bridge) {
>>   		ret = drm_bridge_attach(bridge->encoder, hdmi->next_bridge,
>>   					bridge, flags);
>> @@ -1444,6 +1397,7 @@ static void mtk_hdmi_bridge_atomic_enable(struct drm_bridge *bridge,
>>   }
>>   
>>   static const struct drm_bridge_funcs mtk_hdmi_bridge_funcs = {
>> +	.mode_valid = mtk_hdmi_bridge_mode_valid,
>>   	.atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
>>   	.atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
>>   	.atomic_reset = drm_atomic_helper_bridge_reset,
>> @@ -1454,6 +1408,8 @@ static const struct drm_bridge_funcs mtk_hdmi_bridge_funcs = {
>>   	.mode_set = mtk_hdmi_bridge_mode_set,
>>   	.atomic_pre_enable = mtk_hdmi_bridge_atomic_pre_enable,
>>   	.atomic_enable = mtk_hdmi_bridge_atomic_enable,
>> +	.detect = mtk_hdmi_bridge_detect,
>> +	.get_edid = mtk_hdmi_bridge_get_edid,
>>   };
>>   
>>   static int mtk_hdmi_dt_parse_pdata(struct mtk_hdmi *hdmi,
>> @@ -1762,6 +1718,9 @@ static int mtk_drm_hdmi_probe(struct platform_device *pdev)
>>   
>>   	hdmi->bridge.funcs = &mtk_hdmi_bridge_funcs;
>>   	hdmi->bridge.of_node = pdev->dev.of_node;
>> +	hdmi->bridge.ops = DRM_BRIDGE_OP_DETECT | DRM_BRIDGE_OP_EDID
>> +			   | DRM_BRIDGE_OP_HPD;
> 
> Nitpicking, I'd align the | to the =.
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> 
>> +	hdmi->bridge.type = DRM_MODE_CONNECTOR_HDMIA;
>>   	drm_bridge_add(&hdmi->bridge);
>>   
>>   	ret = mtk_hdmi_clk_enable_audio(hdmi);
>