| Message ID | 20210416092737.1971876-1-narmstrong@baylibre.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | drm/bridge: dw-hdmi: disable loading of DW-HDMI CEC sub-driver | expand |
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(-) >
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(-) >> >
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(-)
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 >
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 >> >
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(-)
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(-)