[PATCH 0/2] drm/bridge: dw-hdmi: disable loading of DW-HDMI CEC sub-driver

[PATCH 0/2] drm/bridge: dw-hdmi: disable loading of DW-HDMI CEC sub-driver

[Neil Armstrong]

This adds DW-HDMI driver a glue option to disable loading of the CEC sub-driver.

On some SoCs, the CEC functionality is enabled in the IP config bits, but the
CEC bus is non-functional like on Amlogic SoCs, where the CEC config bit is set
but the DW-HDMI CEC signal is not connected to a physical pin, leading to some
confusion when the DW-HDMI CEC controller can't communicate on the bus.

Jernej Skrabec (1):
  drm/bridge/synopsys: dw-hdmi: Add an option to suppress loading CEC
    driver

Neil Armstrong (1):
  drm/meson: dw-hdmi: disable DW-HDMI CEC sub-driver

 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 +-
 drivers/gpu/drm/meson/meson_dw_hdmi.c     | 1 +
 include/drm/bridge/dw_hdmi.h              | 2 ++
 3 files changed, 4 insertions(+), 1 deletion(-)

-- 
2.25.1

[PATCH 1/2] drm/bridge/synopsys: dw-hdmi: Add an option to suppress loading CEC driver

[Neil Armstrong]

From: Jernej Skrabec <jernej.skrabec@siol.net>

This adds DW-HDMI driver a glue option to disable loading of the CEC sub-driver.

On some SoCs, the CEC functionality is enabled in the IP config bits, but the
CEC bus is non-functional like on Amlogic SoCs, where the CEC config bit is set
but the DW-HDMI CEC signal is not connected to a physical pin, leading to some
confusion when the DW-HDMI CEC controller can't communicate on the bus.

Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
---
 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 +-
 include/drm/bridge/dw_hdmi.h              | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index dda4fa9a1a08..ae97513ef886 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -3421,7 +3421,7 @@ struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,
 		hdmi->audio = platform_device_register_full(&pdevinfo);
 	}
 
-	if (config0 & HDMI_CONFIG0_CEC) {
+	if (!plat_data->disable_cec && (config0 & HDMI_CONFIG0_CEC)) {
 		cec.hdmi = hdmi;
 		cec.ops = &dw_hdmi_cec_ops;
 		cec.irq = irq;
diff --git a/include/drm/bridge/dw_hdmi.h b/include/drm/bridge/dw_hdmi.h
index ea34ca146b82..6a5716655619 100644
--- a/include/drm/bridge/dw_hdmi.h
+++ b/include/drm/bridge/dw_hdmi.h
@@ -153,6 +153,8 @@ struct dw_hdmi_plat_data {
 	const struct dw_hdmi_phy_config *phy_config;
 	int (*configure_phy)(struct dw_hdmi *hdmi, void *data,
 			     unsigned long mpixelclock);
+
+	unsigned int disable_cec : 1;
 };
 
 struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,
-- 
2.25.1

[PATCH 2/2] drm/meson: dw-hdmi: disable DW-HDMI CEC sub-driver

[Neil Armstrong]

On the Amlogic SoCs, the DW-HDMI HW support is here but the DW-HDMI CEC signal
is not connected to a physical pin, leading to confusion when the dw-hdmi cec
controller can't communicate on the bus.

Disable it to avoid exposing a non-functinal bus.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
---
 drivers/gpu/drm/meson/meson_dw_hdmi.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/meson/meson_dw_hdmi.c b/drivers/gpu/drm/meson/meson_dw_hdmi.c
index aad75a22dc33..2ed87cfdd735 100644
--- a/drivers/gpu/drm/meson/meson_dw_hdmi.c
+++ b/drivers/gpu/drm/meson/meson_dw_hdmi.c
@@ -1103,6 +1103,7 @@ static int meson_dw_hdmi_bind(struct device *dev, struct device *master,
 	dw_plat_data->phy_data = meson_dw_hdmi;
 	dw_plat_data->input_bus_encoding = V4L2_YCBCR_ENC_709;
 	dw_plat_data->ycbcr_420_allowed = true;
+	dw_plat_data->disable_cec = true;
 
 	if (dw_hdmi_is_compatible(meson_dw_hdmi, "amlogic,meson-gxl-dw-hdmi") ||
 	    dw_hdmi_is_compatible(meson_dw_hdmi, "amlogic,meson-gxm-dw-hdmi") ||
-- 
2.25.1

Re: [PATCH 0/2] drm/bridge: dw-hdmi: disable loading of DW-HDMI CEC sub-driver

[Laurent Pinchart]

Hi Neil,

On Fri, Apr 16, 2021 at 11:27:35AM +0200, Neil Armstrong wrote:
> This adds DW-HDMI driver a glue option to disable loading of the CEC sub-driver.
> 
> On some SoCs, the CEC functionality is enabled in the IP config bits, but the
> CEC bus is non-functional like on Amlogic SoCs, where the CEC config bit is set
> but the DW-HDMI CEC signal is not connected to a physical pin, leading to some
> confusion when the DW-HDMI CEC controller can't communicate on the bus.

If we can't trust the CEC config bit, would it be better to not use it
at all, and instead let each platform glue logic tell whether to enable
CEC or not ?

> Jernej Skrabec (1):
>   drm/bridge/synopsys: dw-hdmi: Add an option to suppress loading CEC
>     driver
> 
> Neil Armstrong (1):
>   drm/meson: dw-hdmi: disable DW-HDMI CEC sub-driver
> 
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 +-
>  drivers/gpu/drm/meson/meson_dw_hdmi.c     | 1 +
>  include/drm/bridge/dw_hdmi.h              | 2 ++
>  3 files changed, 4 insertions(+), 1 deletion(-)
> 

-- 
Regards,

Laurent Pinchart

Re: [PATCH 0/2] drm/bridge: dw-hdmi: disable loading of DW-HDMI CEC sub-driver

[Neil Armstrong]

On 16/04/2021 11:58, Laurent Pinchart wrote:
> Hi Neil,
> 
> On Fri, Apr 16, 2021 at 11:27:35AM +0200, Neil Armstrong wrote:
>> This adds DW-HDMI driver a glue option to disable loading of the CEC sub-driver.
>>
>> On some SoCs, the CEC functionality is enabled in the IP config bits, but the
>> CEC bus is non-functional like on Amlogic SoCs, where the CEC config bit is set
>> but the DW-HDMI CEC signal is not connected to a physical pin, leading to some
>> confusion when the DW-HDMI CEC controller can't communicate on the bus.
> 
> If we can't trust the CEC config bit, would it be better to not use it
> at all, and instead let each platform glue logic tell whether to enable
> CEC or not ?

Actually, the CEC config bit is right, the HW exists and should be functional, but
this bit doesn't tell if the CEC signal is connected to something.

This lies in the IP integration, like other bits under the "amlogic,meson-*-dw-hdmi"
umbrella.

The first attempt was by Hans using DT, but adding a property in DT for a vendor
specific compatible doesn't make sense. Another idea would be to describe the
CEC signal endpoint like we do for video signal, but I think this is out of scope and
this solution is much simpler and straightforward, and it's more an exception than
a general use case to solve.

Neil

> 
>> Jernej Skrabec (1):
>>   drm/bridge/synopsys: dw-hdmi: Add an option to suppress loading CEC
>>     driver
>>
>> Neil Armstrong (1):
>>   drm/meson: dw-hdmi: disable DW-HDMI CEC sub-driver
>>
>>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 +-
>>  drivers/gpu/drm/meson/meson_dw_hdmi.c     | 1 +
>>  include/drm/bridge/dw_hdmi.h              | 2 ++
>>  3 files changed, 4 insertions(+), 1 deletion(-)
>>
> 

Re: [PATCH 0/2] drm/bridge: dw-hdmi: disable loading of DW-HDMI CEC sub-driver

[Jernej Škrabec]

CC Hans Verkuil

Dne petek, 16. april 2021 ob 13:38:59 CEST je Neil Armstrong napisal(a):
> On 16/04/2021 11:58, Laurent Pinchart wrote:
> > Hi Neil,
> > 
> > On Fri, Apr 16, 2021 at 11:27:35AM +0200, Neil Armstrong wrote:
> >> This adds DW-HDMI driver a glue option to disable loading of the CEC
> >> sub-driver.
> >> 
> >> On some SoCs, the CEC functionality is enabled in the IP config bits, but
> >> the CEC bus is non-functional like on Amlogic SoCs, where the CEC config
> >> bit is set but the DW-HDMI CEC signal is not connected to a physical
> >> pin, leading to some confusion when the DW-HDMI CEC controller can't
> >> communicate on the bus.> 
> > If we can't trust the CEC config bit, would it be better to not use it
> > at all, and instead let each platform glue logic tell whether to enable
> > CEC or not ?
> 
> Actually, the CEC config bit is right, the HW exists and should be
> functional, but this bit doesn't tell if the CEC signal is connected to
> something.

I'm in favour of Neil's solution. Currently we have only one exception.

> 
> This lies in the IP integration, like other bits under the
> "amlogic,meson-*-dw-hdmi" umbrella.
> 
> The first attempt was by Hans using DT, but adding a property in DT for a
> vendor specific compatible doesn't make sense. Another idea would be to
> describe the CEC signal endpoint like we do for video signal, but I think
> this is out of scope and this solution is much simpler and straightforward,
> and it's more an exception than a general use case to solve.

Note that we still need DT property for disabling CEC. I have one Allwinner H3 
board where board designer decided to use GPIO CEC implementation instead of 
DW HDMI one (vendor Linux doesn't implement DW HDMI CEC driver). Other H3 
boards happily use DW HDMI CEC.

Best regards,
Jernej

> 
> Neil
> 
> >> Jernej Skrabec (1):
> >>   drm/bridge/synopsys: dw-hdmi: Add an option to suppress loading CEC
> >>   
> >>     driver
> >> 
> >> Neil Armstrong (1):
> >>   drm/meson: dw-hdmi: disable DW-HDMI CEC sub-driver
> >>  
> >>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 +-
> >>  drivers/gpu/drm/meson/meson_dw_hdmi.c     | 1 +
> >>  include/drm/bridge/dw_hdmi.h              | 2 ++
> >>  3 files changed, 4 insertions(+), 1 deletion(-)

Re: [PATCH 0/2] drm/bridge: dw-hdmi: disable loading of DW-HDMI CEC sub-driver

[Hans Verkuil]

On 16/04/2021 13:38, Neil Armstrong wrote:
> On 16/04/2021 11:58, Laurent Pinchart wrote:
>> Hi Neil,
>>
>> On Fri, Apr 16, 2021 at 11:27:35AM +0200, Neil Armstrong wrote:
>>> This adds DW-HDMI driver a glue option to disable loading of the CEC sub-driver.
>>>
>>> On some SoCs, the CEC functionality is enabled in the IP config bits, but the
>>> CEC bus is non-functional like on Amlogic SoCs, where the CEC config bit is set
>>> but the DW-HDMI CEC signal is not connected to a physical pin, leading to some
>>> confusion when the DW-HDMI CEC controller can't communicate on the bus.
>>
>> If we can't trust the CEC config bit, would it be better to not use it
>> at all, and instead let each platform glue logic tell whether to enable
>> CEC or not ?
> 
> Actually, the CEC config bit is right, the HW exists and should be functional, but
> this bit doesn't tell if the CEC signal is connected to something.
> 
> This lies in the IP integration, like other bits under the "amlogic,meson-*-dw-hdmi"
> umbrella.
> 
> The first attempt was by Hans using DT, but adding a property in DT for a vendor
> specific compatible doesn't make sense. Another idea would be to describe the
> CEC signal endpoint like we do for video signal, but I think this is out of scope and
> this solution is much simpler and straightforward, and it's more an exception than
> a general use case to solve.

While a DT property might not make sense in this particular case, I still
believe that it is a perfectly valid approach in general: whether or not
the CEC pin is connected is at the hardware level decision, it is not
something that software can detect. If the designer of the board didn't
connect it, then the only place you can define that is in the device tree.

Anyway, for meson I am fine with this solution. At least it prevents creating
a non-functioning cec device. So for this series:

Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Regards,

	Hans

> 
> Neil
> 
>>
>>> Jernej Skrabec (1):
>>>   drm/bridge/synopsys: dw-hdmi: Add an option to suppress loading CEC
>>>     driver
>>>
>>> Neil Armstrong (1):
>>>   drm/meson: dw-hdmi: disable DW-HDMI CEC sub-driver
>>>
>>>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 +-
>>>  drivers/gpu/drm/meson/meson_dw_hdmi.c     | 1 +
>>>  include/drm/bridge/dw_hdmi.h              | 2 ++
>>>  3 files changed, 4 insertions(+), 1 deletion(-)
>>>
>>
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 

Re: [PATCH 0/2] drm/bridge: dw-hdmi: disable loading of DW-HDMI CEC sub-driver

[Neil Armstrong]

On 20/04/2021 17:13, Hans Verkuil wrote:
> On 16/04/2021 13:38, Neil Armstrong wrote:
>> On 16/04/2021 11:58, Laurent Pinchart wrote:
>>> Hi Neil,
>>>
>>> On Fri, Apr 16, 2021 at 11:27:35AM +0200, Neil Armstrong wrote:
>>>> This adds DW-HDMI driver a glue option to disable loading of the CEC sub-driver.
>>>>
>>>> On some SoCs, the CEC functionality is enabled in the IP config bits, but the
>>>> CEC bus is non-functional like on Amlogic SoCs, where the CEC config bit is set
>>>> but the DW-HDMI CEC signal is not connected to a physical pin, leading to some
>>>> confusion when the DW-HDMI CEC controller can't communicate on the bus.
>>>
>>> If we can't trust the CEC config bit, would it be better to not use it
>>> at all, and instead let each platform glue logic tell whether to enable
>>> CEC or not ?
>>
>> Actually, the CEC config bit is right, the HW exists and should be functional, but
>> this bit doesn't tell if the CEC signal is connected to something.
>>
>> This lies in the IP integration, like other bits under the "amlogic,meson-*-dw-hdmi"
>> umbrella.
>>
>> The first attempt was by Hans using DT, but adding a property in DT for a vendor
>> specific compatible doesn't make sense. Another idea would be to describe the
>> CEC signal endpoint like we do for video signal, but I think this is out of scope and
>> this solution is much simpler and straightforward, and it's more an exception than
>> a general use case to solve.
> 
> While a DT property might not make sense in this particular case, I still
> believe that it is a perfectly valid approach in general: whether or not
> the CEC pin is connected is at the hardware level decision, it is not
> something that software can detect. If the designer of the board didn't
> connect it, then the only place you can define that is in the device tree.

Agreed, we need to define a smart way to declare CEC bus relationship in DT, the side
effect would be to handle this particular case.

> 
> Anyway, for meson I am fine with this solution. At least it prevents creating
> a non-functioning cec device. So for this series:
> 
> Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Thanks,

Applying this serie to drm-misc-next

Neil

> 
> Regards,
> 
> 	Hans
> 
>>
>> Neil
>>
>>>
>>>> Jernej Skrabec (1):
>>>>   drm/bridge/synopsys: dw-hdmi: Add an option to suppress loading CEC
>>>>     driver
>>>>
>>>> Neil Armstrong (1):
>>>>   drm/meson: dw-hdmi: disable DW-HDMI CEC sub-driver
>>>>
>>>>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 +-
>>>>  drivers/gpu/drm/meson/meson_dw_hdmi.c     | 1 +
>>>>  include/drm/bridge/dw_hdmi.h              | 2 ++
>>>>  3 files changed, 4 insertions(+), 1 deletion(-)
>>>>
>>>
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>
> 

Re: [PATCH 0/2] drm/bridge: dw-hdmi: disable loading of DW-HDMI CEC sub-driver

[Laurent Pinchart]

On Tue, Apr 20, 2021 at 05:19:52PM +0200, Neil Armstrong wrote:
> On 20/04/2021 17:13, Hans Verkuil wrote:
> > On 16/04/2021 13:38, Neil Armstrong wrote:
> >> On 16/04/2021 11:58, Laurent Pinchart wrote:
> >>> Hi Neil,
> >>>
> >>> On Fri, Apr 16, 2021 at 11:27:35AM +0200, Neil Armstrong wrote:
> >>>> This adds DW-HDMI driver a glue option to disable loading of the CEC sub-driver.
> >>>>
> >>>> On some SoCs, the CEC functionality is enabled in the IP config bits, but the
> >>>> CEC bus is non-functional like on Amlogic SoCs, where the CEC config bit is set
> >>>> but the DW-HDMI CEC signal is not connected to a physical pin, leading to some
> >>>> confusion when the DW-HDMI CEC controller can't communicate on the bus.
> >>>
> >>> If we can't trust the CEC config bit, would it be better to not use it
> >>> at all, and instead let each platform glue logic tell whether to enable
> >>> CEC or not ?
> >>
> >> Actually, the CEC config bit is right, the HW exists and should be functional, but
> >> this bit doesn't tell if the CEC signal is connected to something.
> >>
> >> This lies in the IP integration, like other bits under the "amlogic,meson-*-dw-hdmi"
> >> umbrella.
> >>
> >> The first attempt was by Hans using DT, but adding a property in DT for a vendor
> >> specific compatible doesn't make sense. Another idea would be to describe the
> >> CEC signal endpoint like we do for video signal, but I think this is out of scope and
> >> this solution is much simpler and straightforward, and it's more an exception than
> >> a general use case to solve.
> > 
> > While a DT property might not make sense in this particular case, I still
> > believe that it is a perfectly valid approach in general: whether or not
> > the CEC pin is connected is at the hardware level decision, it is not
> > something that software can detect. If the designer of the board didn't
> > connect it, then the only place you can define that is in the device tree.
> 
> Agreed, we need to define a smart way to declare CEC bus relationship in DT, the side
> effect would be to handle this particular case.

I wonder if it would make sense to use the OF graph bindings to describe
the connection between the CEC controller and the CEC "device" (which I
assume in most cases will be a DT node for a physical connector). Or is
this overkill ?

> > Anyway, for meson I am fine with this solution. At least it prevents creating
> > a non-functioning cec device. So for this series:
> > 
> > Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> 
> Thanks,
> 
> Applying this serie to drm-misc-next
> 
> >>>> Jernej Skrabec (1):
> >>>>   drm/bridge/synopsys: dw-hdmi: Add an option to suppress loading CEC
> >>>>     driver
> >>>>
> >>>> Neil Armstrong (1):
> >>>>   drm/meson: dw-hdmi: disable DW-HDMI CEC sub-driver
> >>>>
> >>>>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 +-
> >>>>  drivers/gpu/drm/meson/meson_dw_hdmi.c     | 1 +
> >>>>  include/drm/bridge/dw_hdmi.h              | 2 ++
> >>>>  3 files changed, 4 insertions(+), 1 deletion(-)

-- 
Regards,

Laurent Pinchart

[PATCH 0/2] drm/sun4i: dw-hdmi: Improve CEC support

[Jernej Skrabec]

It turns out that additional logic between HDMI CEC controller and
pins on PHY on some Allwinner SoCs prevents proper communication.
It might be possible to fix it, but it's much easier and less error
prone to just directly drive pins using software implementation of
CEC protocol.

Let me know what do you think.

Best regards,
Jernej

Jernej Skrabec (2):
  drm/bridge/synopsys: dw-hdmi: Add an option to suppress loading CEC
    driver
  drm/sun4i: dw-hdmi: Bit bang CEC on some SoCs

 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c |  2 +-
 drivers/gpu/drm/sun4i/Kconfig             | 10 +++
 drivers/gpu/drm/sun4i/sun8i_dw_hdmi.h     | 11 +++
 drivers/gpu/drm/sun4i/sun8i_hdmi_phy.c    | 83 ++++++++++++++++++++++-
 include/drm/bridge/dw_hdmi.h              |  2 +
 5 files changed, 105 insertions(+), 3 deletions(-)

-- 
2.21.0

[PATCH 1/2] drm/bridge/synopsys: dw-hdmi: Add an option to suppress loading CEC driver

[Jernej Skrabec]

DW HDMI controller on some Allwinner SoCs has support for CEC, but due
to additional logic put between CEC controller and pins, it doesn't work
correctly, at least not with a lot of instrusive changes. Fortunately,
it's still possible to bitbang protocol.

For such cases, add a platform option to suppress loading CEC driver. If
DW HDMI CEC driver would be loaded, it wouldn't work anyway and only
cause a confusion with multiple /dev entries.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
---
 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 +-
 include/drm/bridge/dw_hdmi.h              | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index a63e5f0dae56..fdda26f8b056 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -2634,7 +2634,7 @@ __dw_hdmi_probe(struct platform_device *pdev,
 		hdmi->audio = platform_device_register_full(&pdevinfo);
 	}
 
-	if (config0 & HDMI_CONFIG0_CEC) {
+	if (!plat_data->is_cec_unusable && (config0 & HDMI_CONFIG0_CEC)) {
 		cec.hdmi = hdmi;
 		cec.ops = &dw_hdmi_cec_ops;
 		cec.irq = irq;
diff --git a/include/drm/bridge/dw_hdmi.h b/include/drm/bridge/dw_hdmi.h
index 66e70770cce5..764b8bcfa62c 100644
--- a/include/drm/bridge/dw_hdmi.h
+++ b/include/drm/bridge/dw_hdmi.h
@@ -144,6 +144,8 @@ struct dw_hdmi_plat_data {
 	int (*configure_phy)(struct dw_hdmi *hdmi,
 			     const struct dw_hdmi_plat_data *pdata,
 			     unsigned long mpixelclock);
+
+	unsigned int is_cec_unusable : 1;
 };
 
 struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,
-- 
2.21.0

Re: [PATCH 1/2] drm/bridge/synopsys: dw-hdmi: Add an option to suppress loading CEC driver

[Laurent Pinchart]

Hi Jernej,

Thank you for the patch.

On Sun, Mar 24, 2019 at 10:21:42PM +0100, Jernej Skrabec wrote:
> DW HDMI controller on some Allwinner SoCs has support for CEC, but due
> to additional logic put between CEC controller and pins, it doesn't work
> correctly, at least not with a lot of instrusive changes. Fortunately,
> it's still possible to bitbang protocol.
> 
> For such cases, add a platform option to suppress loading CEC driver. If
> DW HDMI CEC driver would be loaded, it wouldn't work anyway and only
> cause a confusion with multiple /dev entries.
> 
> Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
> ---
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 +-
>  include/drm/bridge/dw_hdmi.h              | 2 ++
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index a63e5f0dae56..fdda26f8b056 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -2634,7 +2634,7 @@ __dw_hdmi_probe(struct platform_device *pdev,
>  		hdmi->audio = platform_device_register_full(&pdevinfo);
>  	}
>  
> -	if (config0 & HDMI_CONFIG0_CEC) {
> +	if (!plat_data->is_cec_unusable && (config0 & HDMI_CONFIG0_CEC)) {
>  		cec.hdmi = hdmi;
>  		cec.ops = &dw_hdmi_cec_ops;
>  		cec.irq = irq;
> diff --git a/include/drm/bridge/dw_hdmi.h b/include/drm/bridge/dw_hdmi.h
> index 66e70770cce5..764b8bcfa62c 100644
> --- a/include/drm/bridge/dw_hdmi.h
> +++ b/include/drm/bridge/dw_hdmi.h
> @@ -144,6 +144,8 @@ struct dw_hdmi_plat_data {
>  	int (*configure_phy)(struct dw_hdmi *hdmi,
>  			     const struct dw_hdmi_plat_data *pdata,
>  			     unsigned long mpixelclock);
> +
> +	unsigned int is_cec_unusable : 1;

Strictly speaking your CEC controller isn't unusable, it's just a bit
difficult to use it according to your commit message. Would disable_cec
be a more appropriate field name ? And how difficult would it be to
support the hardware CEC controller, would that result in changes that
could be useful to other vendors too ?

>  };
>  
>  struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,

-- 
Regards,

Laurent Pinchart

Re: [PATCH 1/2] drm/bridge/synopsys: dw-hdmi: Add an option to suppress loading CEC driver

[Jernej Škrabec]

Dne ponedeljek, 25. marec 2019 ob 02:35:31 CET je Laurent Pinchart napisal(a):
> Hi Jernej,
> 
> Thank you for the patch.
> 
> On Sun, Mar 24, 2019 at 10:21:42PM +0100, Jernej Skrabec wrote:
> > DW HDMI controller on some Allwinner SoCs has support for CEC, but due
> > to additional logic put between CEC controller and pins, it doesn't work
> > correctly, at least not with a lot of instrusive changes. Fortunately,
> > it's still possible to bitbang protocol.
> > 
> > For such cases, add a platform option to suppress loading CEC driver. If
> > DW HDMI CEC driver would be loaded, it wouldn't work anyway and only
> > cause a confusion with multiple /dev entries.
> > 
> > Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
> > ---
> > 
> >  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 +-
> >  include/drm/bridge/dw_hdmi.h              | 2 ++
> >  2 files changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c index
> > a63e5f0dae56..fdda26f8b056 100644
> > --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > @@ -2634,7 +2634,7 @@ __dw_hdmi_probe(struct platform_device *pdev,
> > 
> >  		hdmi->audio = platform_device_register_full(&pdevinfo);
> >  	
> >  	}
> > 
> > -	if (config0 & HDMI_CONFIG0_CEC) {
> > +	if (!plat_data->is_cec_unusable && (config0 & HDMI_CONFIG0_CEC)) {
> > 
> >  		cec.hdmi = hdmi;
> >  		cec.ops = &dw_hdmi_cec_ops;
> >  		cec.irq = irq;
> > 
> > diff --git a/include/drm/bridge/dw_hdmi.h b/include/drm/bridge/dw_hdmi.h
> > index 66e70770cce5..764b8bcfa62c 100644
> > --- a/include/drm/bridge/dw_hdmi.h
> > +++ b/include/drm/bridge/dw_hdmi.h
> > @@ -144,6 +144,8 @@ struct dw_hdmi_plat_data {
> > 
> >  	int (*configure_phy)(struct dw_hdmi *hdmi,
> >  	
> >  			     const struct dw_hdmi_plat_data *pdata,
> >  			     unsigned long mpixelclock);
> > 
> > +
> > +	unsigned int is_cec_unusable : 1;
> 
> Strictly speaking your CEC controller isn't unusable, it's just a bit
> difficult to use it according to your commit message. Would disable_cec
> be a more appropriate field name ? And how difficult would it be to
> support the hardware CEC controller, would that result in changes that
> could be useful to other vendors too ?

Ok, maybe naming of the variable is a bit harsh. Currently I don't know any 
other hardware with the same issue. While I don't know CEC protocol or DW HDMI 
CEC controller very well, I think it would be difficult to implement change of 
direction during ACK transmission. At that time, packet is not fully received 
or transmitted, so I doubt we could use any interrupt for that. In any case, I 
don't think it's worth the hassle and we should just use proven software 
implementation.

Early attempt on fixing this on kernel provided by Allwinner resulted in very 
ugly code and I'm not sure it works 100% (driver based on i.MX6 one):
https://github.com/jernejsk/OpenELEC-OPi2/blob/openelec-7.0/projects/H3/
patches/linux/linux-008-add-hw-hdmi-cec-support.patch#L1321

> 
> >  };
> >  
> >  struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,

Re: [PATCH 1/2] drm/bridge/synopsys: dw-hdmi: Add an option to suppress loading CEC driver

[Neil Armstrong]

Le 25/03/2019 02:35, Laurent Pinchart a écrit :
> Hi Jernej,
> 
> Thank you for the patch.
> 
> On Sun, Mar 24, 2019 at 10:21:42PM +0100, Jernej Skrabec wrote:
>> DW HDMI controller on some Allwinner SoCs has support for CEC, but due
>> to additional logic put between CEC controller and pins, it doesn't work
>> correctly, at least not with a lot of instrusive changes. Fortunately,
>> it's still possible to bitbang protocol.
>>
>> For such cases, add a platform option to suppress loading CEC driver. If
>> DW HDMI CEC driver would be loaded, it wouldn't work anyway and only
>> cause a confusion with multiple /dev entries.
>>
>> Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
>> ---
>>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 2 +-
>>  include/drm/bridge/dw_hdmi.h              | 2 ++
>>  2 files changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>> index a63e5f0dae56..fdda26f8b056 100644
>> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
>> @@ -2634,7 +2634,7 @@ __dw_hdmi_probe(struct platform_device *pdev,
>>  		hdmi->audio = platform_device_register_full(&pdevinfo);
>>  	}
>>  
>> -	if (config0 & HDMI_CONFIG0_CEC) {
>> +	if (!plat_data->is_cec_unusable && (config0 & HDMI_CONFIG0_CEC)) {
>>  		cec.hdmi = hdmi;
>>  		cec.ops = &dw_hdmi_cec_ops;
>>  		cec.irq = irq;
>> diff --git a/include/drm/bridge/dw_hdmi.h b/include/drm/bridge/dw_hdmi.h
>> index 66e70770cce5..764b8bcfa62c 100644
>> --- a/include/drm/bridge/dw_hdmi.h
>> +++ b/include/drm/bridge/dw_hdmi.h
>> @@ -144,6 +144,8 @@ struct dw_hdmi_plat_data {
>>  	int (*configure_phy)(struct dw_hdmi *hdmi,
>>  			     const struct dw_hdmi_plat_data *pdata,
>>  			     unsigned long mpixelclock);
>> +
>> +	unsigned int is_cec_unusable : 1;
> 
> Strictly speaking your CEC controller isn't unusable, it's just a bit
> difficult to use it according to your commit message. Would disable_cec
> be a more appropriate field name ? 

Actually, it would be useful to have in for Amlogic SoCs also, the dw-hdmi
is configured with the CEC engine, but isn't connected to an external I/O.
And we have easy way to disable it unless disabling the DW-HDMI CEC driver...
With a more appropriate name,
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>

> And how difficult would it be to
> support the hardware CEC controller, would that result in changes that
> could be useful to other vendors too ?
> 
>>  };
>>  
>>  struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,
>