[PATCH V4] drm/stm: Fix bus_flags handling

[PATCH V4] drm/stm: Fix bus_flags handling

[Marek Vasut]

The drm_display_mode_to_videomode() does not populate DISPLAY_FLAGS_DE_LOW
or DISPLAY_FLAGS_PIXDATA_NEGEDGE flags in struct videomode. Therefore, no
matter what polarity the next bridge or display might require, these flags
are never set, and thus the LTDC GCR_DEPOL and GCR_PCPOL bits are never set,
and the LTDC behaves as if both DISPLAY_FLAGS_PIXDATA_POSEDGE and
DISPLAY_FLAGS_DE_HIGH were always set.

The fix for this problem is taken almost verbatim from MXSFB driver. In
case there is a bridge attached to the LTDC, the bridge might have extra
polarity requirements, so extract bus_flags from the bridge and use them
for LTDC configuration. Otherwise, extract bus_flags from the connector,
which is the display.

Fixes: b759012c5fa7 ("drm/stm: Add STM32 LTDC driver")
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Yannick Fertre <yannick.fertre@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Antonio Borneo <antonio.borneo@st.com>
Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Philippe Cornu <philippe.cornu@st.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Vincent Abriou <vincent.abriou@st.com>
Cc: Yannick Fertre <yannick.fertre@st.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-stm32@st-md-mailman.stormreply.com
To: dri-devel@lists.freedesktop.org
---
V2: Check if ldev->bridge->timings is non-NULL before accessing it
V3: get bus_flags from connector (from Yannick)
    - Display controller could support several connectors (not connected at
      the same time). ie: stm32mp15c-DK2 board have 2 connectors (HDMI + DSI).
      Driver check which connector is connected to get the bus flag.
V4: get bridge from encoder (from Yannick)
---
 drivers/gpu/drm/stm/ltdc.c | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
index 6e28e6b60e72..acc9f6694eb6 100644
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -544,13 +544,42 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
 {
 	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
 	struct drm_device *ddev = crtc->dev;
+	struct drm_connector_list_iter iter;
+	struct drm_connector *connector = NULL;
+	struct drm_encoder *encoder = NULL;
+	struct drm_bridge *bridge = NULL;
 	struct drm_display_mode *mode = &crtc->state->adjusted_mode;
 	struct videomode vm;
 	u32 hsync, vsync, accum_hbp, accum_vbp, accum_act_w, accum_act_h;
 	u32 total_width, total_height;
+	u32 bus_flags = 0;
 	u32 val;
 	int ret;
 
+	/* get encoder from crtc */
+	drm_for_each_encoder(encoder, ddev)
+		if (encoder->crtc == crtc)
+			break;
+
+	if (encoder) {
+		/* get bridge from encoder */
+		list_for_each_entry(bridge, &encoder->bridge_chain, chain_node)
+			if (bridge->encoder == encoder)
+				break;
+
+		/* Get the connector from encoder */
+		drm_connector_list_iter_begin(ddev, &iter);
+		drm_for_each_connector_iter(connector, &iter)
+			if (connector->encoder == encoder)
+				break;
+		drm_connector_list_iter_end(&iter);
+	}
+
+	if (bridge && bridge->timings)
+		bus_flags = bridge->timings->input_bus_flags;
+	else if (connector)
+		bus_flags = connector->display_info.bus_flags;
+
 	if (!pm_runtime_active(ddev->dev)) {
 		ret = pm_runtime_get_sync(ddev->dev);
 		if (ret) {
@@ -586,10 +615,10 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
 	if (vm.flags & DISPLAY_FLAGS_VSYNC_HIGH)
 		val |= GCR_VSPOL;
 
-	if (vm.flags & DISPLAY_FLAGS_DE_LOW)
+	if (bus_flags & DRM_BUS_FLAG_DE_LOW)
 		val |= GCR_DEPOL;
 
-	if (vm.flags & DISPLAY_FLAGS_PIXDATA_NEGEDGE)
+	if (bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE)
 		val |= GCR_PCPOL;
 
 	reg_update_bits(ldev->regs, LTDC_GCR,
-- 
2.29.2


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Re: [PATCH V4] drm/stm: Fix bus_flags handling

[yannick Fertre]

Hi Marek,
Thanks for the patch.

Tested-by: Yannick Fertre <yannick.fertre@foss.st.com>



On 1/27/21 12:07 PM, Marek Vasut wrote:
> The drm_display_mode_to_videomode() does not populate DISPLAY_FLAGS_DE_LOW
> or DISPLAY_FLAGS_PIXDATA_NEGEDGE flags in struct videomode. Therefore, no
> matter what polarity the next bridge or display might require, these flags
> are never set, and thus the LTDC GCR_DEPOL and GCR_PCPOL bits are never set,
> and the LTDC behaves as if both DISPLAY_FLAGS_PIXDATA_POSEDGE and
> DISPLAY_FLAGS_DE_HIGH were always set.
> 
> The fix for this problem is taken almost verbatim from MXSFB driver. In
> case there is a bridge attached to the LTDC, the bridge might have extra
> polarity requirements, so extract bus_flags from the bridge and use them
> for LTDC configuration. Otherwise, extract bus_flags from the connector,
> which is the display.
> 
> Fixes: b759012c5fa7 ("drm/stm: Add STM32 LTDC driver")
> Signed-off-by: Marek Vasut <marex@denx.de>
> Signed-off-by: Yannick Fertre <yannick.fertre@st.com>
> Cc: Alexandre Torgue <alexandre.torgue@st.com>
> Cc: Antonio Borneo <antonio.borneo@st.com>
> Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
> Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
> Cc: Philippe Cornu <philippe.cornu@st.com>
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Cc: Vincent Abriou <vincent.abriou@st.com>
> Cc: Yannick Fertre <yannick.fertre@st.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-stm32@st-md-mailman.stormreply.com
> To: dri-devel@lists.freedesktop.org
> ---
> V2: Check if ldev->bridge->timings is non-NULL before accessing it
> V3: get bus_flags from connector (from Yannick)
>      - Display controller could support several connectors (not connected at
>        the same time). ie: stm32mp15c-DK2 board have 2 connectors (HDMI + DSI).
>        Driver check which connector is connected to get the bus flag.
> V4: get bridge from encoder (from Yannick)
> ---
>   drivers/gpu/drm/stm/ltdc.c | 33 +++++++++++++++++++++++++++++++--
>   1 file changed, 31 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
> index 6e28e6b60e72..acc9f6694eb6 100644
> --- a/drivers/gpu/drm/stm/ltdc.c
> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -544,13 +544,42 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
>   {
>   	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
>   	struct drm_device *ddev = crtc->dev;
> +	struct drm_connector_list_iter iter;
> +	struct drm_connector *connector = NULL;
> +	struct drm_encoder *encoder = NULL;
> +	struct drm_bridge *bridge = NULL;
>   	struct drm_display_mode *mode = &crtc->state->adjusted_mode;
>   	struct videomode vm;
>   	u32 hsync, vsync, accum_hbp, accum_vbp, accum_act_w, accum_act_h;
>   	u32 total_width, total_height;
> +	u32 bus_flags = 0;
>   	u32 val;
>   	int ret;
>   
> +	/* get encoder from crtc */
> +	drm_for_each_encoder(encoder, ddev)
> +		if (encoder->crtc == crtc)
> +			break;
> +
> +	if (encoder) {
> +		/* get bridge from encoder */
> +		list_for_each_entry(bridge, &encoder->bridge_chain, chain_node)
> +			if (bridge->encoder == encoder)
> +				break;
> +
> +		/* Get the connector from encoder */
> +		drm_connector_list_iter_begin(ddev, &iter);
> +		drm_for_each_connector_iter(connector, &iter)
> +			if (connector->encoder == encoder)
> +				break;
> +		drm_connector_list_iter_end(&iter);
> +	}
> +
> +	if (bridge && bridge->timings)
> +		bus_flags = bridge->timings->input_bus_flags;
> +	else if (connector)
> +		bus_flags = connector->display_info.bus_flags;
> +
>   	if (!pm_runtime_active(ddev->dev)) {
>   		ret = pm_runtime_get_sync(ddev->dev);
>   		if (ret) {
> @@ -586,10 +615,10 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
>   	if (vm.flags & DISPLAY_FLAGS_VSYNC_HIGH)
>   		val |= GCR_VSPOL;
>   
> -	if (vm.flags & DISPLAY_FLAGS_DE_LOW)
> +	if (bus_flags & DRM_BUS_FLAG_DE_LOW)
>   		val |= GCR_DEPOL;
>   
> -	if (vm.flags & DISPLAY_FLAGS_PIXDATA_NEGEDGE)
> +	if (bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE)
>   		val |= GCR_PCPOL;
>   
>   	reg_update_bits(ldev->regs, LTDC_GCR,
> 

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RE: [PATCH V4] drm/stm: Fix bus_flags handling

[Philippe CORNU]

Dear Marek,
Applied on drm-misc-next.
Many thanks for your patch,
Philippe :-)


ST Restricted

-----Original Message-----
From: Marek Vasut <marex@denx.de> 
Sent: Wednesday, January 27, 2021 12:08
To: dri-devel@lists.freedesktop.org
Cc: Marek Vasut <marex@denx.de>; Yannick FERTRE <yannick.fertre@st.com>; Alexandre TORGUE <alexandre.torgue@st.com>; Antonio BORNEO <antonio.borneo@st.com>; Benjamin Gaignard <benjamin.gaignard@st.com>; Maxime Coquelin <mcoquelin.stm32@gmail.com>; Philippe CORNU <philippe.cornu@st.com>; Sam Ravnborg <sam@ravnborg.org>; Vincent ABRIOU <vincent.abriou@st.com>; linux-arm-kernel@lists.infradead.org; linux-stm32@st-md-mailman.stormreply.com
Subject: [PATCH V4] drm/stm: Fix bus_flags handling

The drm_display_mode_to_videomode() does not populate DISPLAY_FLAGS_DE_LOW or DISPLAY_FLAGS_PIXDATA_NEGEDGE flags in struct videomode. Therefore, no matter what polarity the next bridge or display might require, these flags are never set, and thus the LTDC GCR_DEPOL and GCR_PCPOL bits are never set, and the LTDC behaves as if both DISPLAY_FLAGS_PIXDATA_POSEDGE and DISPLAY_FLAGS_DE_HIGH were always set.

The fix for this problem is taken almost verbatim from MXSFB driver. In case there is a bridge attached to the LTDC, the bridge might have extra polarity requirements, so extract bus_flags from the bridge and use them for LTDC configuration. Otherwise, extract bus_flags from the connector, which is the display.

Fixes: b759012c5fa7 ("drm/stm: Add STM32 LTDC driver")
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Yannick Fertre <yannick.fertre@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Antonio Borneo <antonio.borneo@st.com>
Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Philippe Cornu <philippe.cornu@st.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Vincent Abriou <vincent.abriou@st.com>
Cc: Yannick Fertre <yannick.fertre@st.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-stm32@st-md-mailman.stormreply.com
To: dri-devel@lists.freedesktop.org
---
V2: Check if ldev->bridge->timings is non-NULL before accessing it
V3: get bus_flags from connector (from Yannick)
    - Display controller could support several connectors (not connected at
      the same time). ie: stm32mp15c-DK2 board have 2 connectors (HDMI + DSI).
      Driver check which connector is connected to get the bus flag.
V4: get bridge from encoder (from Yannick)
---
 drivers/gpu/drm/stm/ltdc.c | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c index 6e28e6b60e72..acc9f6694eb6 100644
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -544,13 +544,42 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)  {
 	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
 	struct drm_device *ddev = crtc->dev;
+	struct drm_connector_list_iter iter;
+	struct drm_connector *connector = NULL;
+	struct drm_encoder *encoder = NULL;
+	struct drm_bridge *bridge = NULL;
 	struct drm_display_mode *mode = &crtc->state->adjusted_mode;
 	struct videomode vm;
 	u32 hsync, vsync, accum_hbp, accum_vbp, accum_act_w, accum_act_h;
 	u32 total_width, total_height;
+	u32 bus_flags = 0;
 	u32 val;
 	int ret;
 
+	/* get encoder from crtc */
+	drm_for_each_encoder(encoder, ddev)
+		if (encoder->crtc == crtc)
+			break;
+
+	if (encoder) {
+		/* get bridge from encoder */
+		list_for_each_entry(bridge, &encoder->bridge_chain, chain_node)
+			if (bridge->encoder == encoder)
+				break;
+
+		/* Get the connector from encoder */
+		drm_connector_list_iter_begin(ddev, &iter);
+		drm_for_each_connector_iter(connector, &iter)
+			if (connector->encoder == encoder)
+				break;
+		drm_connector_list_iter_end(&iter);
+	}
+
+	if (bridge && bridge->timings)
+		bus_flags = bridge->timings->input_bus_flags;
+	else if (connector)
+		bus_flags = connector->display_info.bus_flags;
+
 	if (!pm_runtime_active(ddev->dev)) {
 		ret = pm_runtime_get_sync(ddev->dev);
 		if (ret) {
@@ -586,10 +615,10 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
 	if (vm.flags & DISPLAY_FLAGS_VSYNC_HIGH)
 		val |= GCR_VSPOL;
 
-	if (vm.flags & DISPLAY_FLAGS_DE_LOW)
+	if (bus_flags & DRM_BUS_FLAG_DE_LOW)
 		val |= GCR_DEPOL;
 
-	if (vm.flags & DISPLAY_FLAGS_PIXDATA_NEGEDGE)
+	if (bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE)
 		val |= GCR_PCPOL;
 
 	reg_update_bits(ldev->regs, LTDC_GCR,
--
2.29.2

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