| Message ID | 20230314115644.3775169-1-gerald.loacker@wolfvision.net |
|---|---|
| Headers | show |
| Series | Add timing override to sitronix,st7789v | expand |
On 14/03/2023 12:56, Gerald Loacker wrote: > The sitronix-st7789v driver now considers the panel-timing property. > Add the property to the documentation. > > Signed-off-by: Gerald Loacker <gerald.loacker@wolfvision.net> Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> Best regards, Krzysztof
On Wed, Mar 29, 2023 at 12:08:50PM +0200, Michael Riesch wrote: > On 3/29/23 11:16, Maxime Ripard wrote: > > On Thu, Mar 16, 2023 at 11:29:53PM +0100, Michael Riesch wrote: > >> Hi Rob, > >> > >> On 3/16/23 22:57, Rob Herring wrote: > >>> On Tue, Mar 14, 2023 at 12:56:44PM +0100, Gerald Loacker wrote: > >>>> The sitronix-st7789v driver now considers the panel-timing property. > >>> > >>> I read the patch for that and still don't know 'why'. Commit messages > >>> should answer why. > >>> > >>>> Add the property to the documentation. > >>> > >>> We generally don't put timings in DT for panels. Why is this one > >>> special? > >> > >> For now, having the timings in the device tree allows for setting the > >> hsync/vsync/de polarity. > >> > >> As a next step, we aim to implement the partial mode feature of this > >> panel. It is possible to use only a certain region of the panel, which > >> is helpful e.g., when a part of the panel is occluded and should not be > >> considered by DRM. We thought that this could be specified as timing in DT. > >> > >> (The hactive and vactive properties serve as dimensions of this certain > >> region, of course. We still need to specify somehow the position of the > >> region. Maybe with additional properties hactive-start and vactive-start?) > >> > >> What do you think about that? > > > > I don't see why we would need the device tree to support that. What you > > described is essentially what overscan is for HDMI/analog output, and we > > already have everything to deal with overscan properly in KMS. > > Thanks for your response, but I am afraid I don't quite follow. > > How are we supposed to expose control over the hsync/vsync/data enable > polarity? I only know that the display controller and the panel need to > agree on a setting that works for both. What is the canonical way to do > this? So typically, it would come from the panel datasheet and would thus be exposed by the panel driver. st7789v is not a panel itself but a (pretty flexible) panel controller so it's not fixed and I don't think we have a good answer to that (yet). > A different question is the partial mode, for which (IIUC) you suggest > the overscan feature. As I have never heard of this before, it would be > very nice if you could point me to some examples. Where would the > effective resolution be set in this case? So, back when CRT were a thing the edges of the tube were masked by the plastic case. HDMI inherited from that and that's why you still have some UI on some devices (like consoles) to setup the active area of the display. The underlying issue is exactly what you describe: the active area is larger than what the plastic case allows to see. I don't think anyone ever had the usecase you have, but it would be the right solution to me to solve essentially the same issue the same way we do on other output types. Maxime
Hi Maxime, On 3/30/23 16:58, Maxime Ripard wrote: > On Wed, Mar 29, 2023 at 12:08:50PM +0200, Michael Riesch wrote: >> On 3/29/23 11:16, Maxime Ripard wrote: >>> On Thu, Mar 16, 2023 at 11:29:53PM +0100, Michael Riesch wrote: >>>> Hi Rob, >>>> >>>> On 3/16/23 22:57, Rob Herring wrote: >>>>> On Tue, Mar 14, 2023 at 12:56:44PM +0100, Gerald Loacker wrote: >>>>>> The sitronix-st7789v driver now considers the panel-timing property. >>>>> >>>>> I read the patch for that and still don't know 'why'. Commit messages >>>>> should answer why. >>>>> >>>>>> Add the property to the documentation. >>>>> >>>>> We generally don't put timings in DT for panels. Why is this one >>>>> special? >>>> >>>> For now, having the timings in the device tree allows for setting the >>>> hsync/vsync/de polarity. >>>> >>>> As a next step, we aim to implement the partial mode feature of this >>>> panel. It is possible to use only a certain region of the panel, which >>>> is helpful e.g., when a part of the panel is occluded and should not be >>>> considered by DRM. We thought that this could be specified as timing in DT. >>>> >>>> (The hactive and vactive properties serve as dimensions of this certain >>>> region, of course. We still need to specify somehow the position of the >>>> region. Maybe with additional properties hactive-start and vactive-start?) >>>> >>>> What do you think about that? >>> >>> I don't see why we would need the device tree to support that. What you >>> described is essentially what overscan is for HDMI/analog output, and we >>> already have everything to deal with overscan properly in KMS. >> >> Thanks for your response, but I am afraid I don't quite follow. >> >> How are we supposed to expose control over the hsync/vsync/data enable >> polarity? I only know that the display controller and the panel need to >> agree on a setting that works for both. What is the canonical way to do >> this? > > So typically, it would come from the panel datasheet and would thus be > exposed by the panel driver. st7789v is not a panel itself but a (pretty > flexible) panel controller so it's not fixed and I don't think we have a > good answer to that (yet). Then it seems to me that creating a panel driver (= st8879v panel controller driver with a new compatible) would make sense. By coincidence Sebastian Reichel has come up with this approach recently, see https://lore.kernel.org/dri-devel/20230317232355.1554980-1-sre@kernel.org/ We just need a way to resolve the conflicts between the two series. Cc: Sebastian >> A different question is the partial mode, for which (IIUC) you suggest >> the overscan feature. As I have never heard of this before, it would be >> very nice if you could point me to some examples. Where would the >> effective resolution be set in this case? > > So, back when CRT were a thing the edges of the tube were masked by the > plastic case. HDMI inherited from that and that's why you still have > some UI on some devices (like consoles) to setup the active area of the > display. > > The underlying issue is exactly what you describe: the active area is > larger than what the plastic case allows to see. I don't think anyone > ever had the usecase you have, but it would be the right solution to me > to solve essentially the same issue the same way we do on other output > types. OK, we'll look into the overscan feature. But still the information about the active area should come from the driver, right? Thanks and best regards, Michael
Hi all, On 3/14/23 12:56, Gerald Loacker wrote: > This patch set adds additional functionality to the sitronix,st7789v > driver. > > Patches 1,3 and 4 propagate useful flags to the drm subsystem. > Patch 2 adds the orientation property. If there are no objections, patches 1-4 and 6 could be applied from our point of view. Or should we spin a v2? > Patch 5 parses the device tree for a panel-timing and makes it possible to > override the default timing. > Patches 6 and 7 add the new properties to the dt-bindings. Parsing the timing from the device tree (patches 5 and 7) can be ignored, we'll come up with a different approach. Best regards, Michael > > Gerald Loacker (4): > drm/panel: sitronix-st7789v: propagate h/v-sync polarity > drm/panel: sitronix-st7789v: add bus_flags to connector > drm/panel: sitronix-st7789v: parse device tree to override timing mode > dt-bindings: display: add panel-timing property to sitronix,st7789v > > Michael Riesch (3): > drm/panel: sitronix-st7789v: propagate RGB666 format > drm/panel: sitronix-st7789v: add panel orientation support > dt-bindings: display: add rotation property to sitronix,st7789v > > .../display/panel/sitronix,st7789v.yaml | 19 ++ > .../gpu/drm/panel/panel-sitronix-st7789v.c | 204 +++++++++++++++--- > 2 files changed, 191 insertions(+), 32 deletions(-) >
On Fri, Mar 31, 2023 at 11:36:43AM +0200, Michael Riesch wrote: > On 3/30/23 16:58, Maxime Ripard wrote: > > On Wed, Mar 29, 2023 at 12:08:50PM +0200, Michael Riesch wrote: > >> On 3/29/23 11:16, Maxime Ripard wrote: > >>> On Thu, Mar 16, 2023 at 11:29:53PM +0100, Michael Riesch wrote: > >>>> Hi Rob, > >>>> > >>>> On 3/16/23 22:57, Rob Herring wrote: > >>>>> On Tue, Mar 14, 2023 at 12:56:44PM +0100, Gerald Loacker wrote: > >>>>>> The sitronix-st7789v driver now considers the panel-timing property. > >>>>> > >>>>> I read the patch for that and still don't know 'why'. Commit messages > >>>>> should answer why. > >>>>> > >>>>>> Add the property to the documentation. > >>>>> > >>>>> We generally don't put timings in DT for panels. Why is this one > >>>>> special? > >>>> > >>>> For now, having the timings in the device tree allows for setting the > >>>> hsync/vsync/de polarity. > >>>> > >>>> As a next step, we aim to implement the partial mode feature of this > >>>> panel. It is possible to use only a certain region of the panel, which > >>>> is helpful e.g., when a part of the panel is occluded and should not be > >>>> considered by DRM. We thought that this could be specified as timing in DT. > >>>> > >>>> (The hactive and vactive properties serve as dimensions of this certain > >>>> region, of course. We still need to specify somehow the position of the > >>>> region. Maybe with additional properties hactive-start and vactive-start?) > >>>> > >>>> What do you think about that? > >>> > >>> I don't see why we would need the device tree to support that. What you > >>> described is essentially what overscan is for HDMI/analog output, and we > >>> already have everything to deal with overscan properly in KMS. > >> > >> Thanks for your response, but I am afraid I don't quite follow. > >> > >> How are we supposed to expose control over the hsync/vsync/data enable > >> polarity? I only know that the display controller and the panel need to > >> agree on a setting that works for both. What is the canonical way to do > >> this? > > > > So typically, it would come from the panel datasheet and would thus be > > exposed by the panel driver. st7789v is not a panel itself but a (pretty > > flexible) panel controller so it's not fixed and I don't think we have a > > good answer to that (yet). > > Then it seems to me that creating a panel driver (= st8879v panel > controller driver with a new compatible) would make sense. I don't see why? The entire controller is the same except (maybe) for some initialization data. Doing a new driver for it seems like taking the easy way out? > By coincidence Sebastian Reichel has come up with this approach > recently, see > https://lore.kernel.org/dri-devel/20230317232355.1554980-1-sre@kernel.org/ > We just need a way to resolve the conflicts between the two series. > > Cc: Sebastian That's not a new driver though? That approach looks sane to me. > >> A different question is the partial mode, for which (IIUC) you suggest > >> the overscan feature. As I have never heard of this before, it would be > >> very nice if you could point me to some examples. Where would the > >> effective resolution be set in this case? > > > > So, back when CRT were a thing the edges of the tube were masked by the > > plastic case. HDMI inherited from that and that's why you still have > > some UI on some devices (like consoles) to setup the active area of the > > display. > > > > The underlying issue is exactly what you describe: the active area is > > larger than what the plastic case allows to see. I don't think anyone > > ever had the usecase you have, but it would be the right solution to me > > to solve essentially the same issue the same way we do on other output > > types. > > OK, we'll look into the overscan feature. But still the information > about the active area should come from the driver, right? No, the userspace is in charge there. Maxime
On Tue, Apr 04, 2023 at 06:26:25PM +0200, Michael Riesch wrote: > >>>> A different question is the partial mode, for which (IIUC) you suggest > >>>> the overscan feature. As I have never heard of this before, it would be > >>>> very nice if you could point me to some examples. Where would the > >>>> effective resolution be set in this case? > >>> > >>> So, back when CRT were a thing the edges of the tube were masked by the > >>> plastic case. HDMI inherited from that and that's why you still have > >>> some UI on some devices (like consoles) to setup the active area of the > >>> display. > >>> > >>> The underlying issue is exactly what you describe: the active area is > >>> larger than what the plastic case allows to see. I don't think anyone > >>> ever had the usecase you have, but it would be the right solution to me > >>> to solve essentially the same issue the same way we do on other output > >>> types. > >> > >> OK, we'll look into the overscan feature. But still the information > >> about the active area should come from the driver, right? > > > > No, the userspace is in charge there. > > I'd prefer not to have the hardware description in user space. But we > can continue this discussing once our v2 is out. I'm not sure if it's worth doing something if you don't agree with it :) At the end of the day, "the hardware" is a matter of semantics, and you would argue that it's only the (user) visible part of the display, and I would argue that it's the whole panel and we would both be somewhat right. The thing is: having the margins definition allows the userspace to be aware that there's overscan to deal with, and for example setup the scaler to properly display whatever you put in there. If you just report a weird mode that doesn't match any kind of standard, well, you could still do that, but you would need to tell the compositor which mode you would need to scale down from. In both case the userspace is involved. One is generic, the other isn't and probably requires some extra development. Maxime