| Message ID | 20161116093732.12828-1-wens@csie.org (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
On Wed, Nov 16, 2016 at 05:37:31PM +0800, Chen-Yu Tsai wrote: > The sun4i DRM driver counts the number of endpoints it found and > registers the whole DRM pipeline if any endpoints are found. > > However, if the TCON and its child endpoints (LCD panels, TV encoder, > HDMI encoder, MIPI DSI encoder, etc.) aren't found, that means we > don't have any usable CRTCs, and the display pipeline is incomplete > and useless. If some node set as available is not probed, then yes, it does, but I'm not really sure how it's a problem. Quite the opposite actually. > The whole DRM display pipeline should only be registered and enabled > if there are proper outputs available. Unless I've misunderstood what you're saying, we could have the writeback for example that would just need the display engine. > The debug message "Queued %d outputs on pipeline %d\n" is also telling. > > This patch makes the driver only count enabled TCON endpoints. If > none are found, the DRM pipeline is not used. This avoids screwing > up the simple framebuffer provided by the bootloader in cases where > we aren't able to support the display with the DRM subsystem, due > to lack of panel or bridge drivers, or just lack of progress. The framebuffer is removed only at bind time, which means that all the drivers have probed already. Lack of progress isn't an issue here, since the node simply won't be there, and we wouldn't have it in the component lists. And lack of drivers shouldn't be an issue either, since in order for bind to be called, all the drivers would have gone through their probe. So I'm not really sure what it fixes. Maxime
On Fri, Nov 18, 2016 at 3:02 AM, Maxime Ripard <maxime.ripard@free-electrons.com> wrote: > On Wed, Nov 16, 2016 at 05:37:31PM +0800, Chen-Yu Tsai wrote: >> The sun4i DRM driver counts the number of endpoints it found and >> registers the whole DRM pipeline if any endpoints are found. >> >> However, if the TCON and its child endpoints (LCD panels, TV encoder, >> HDMI encoder, MIPI DSI encoder, etc.) aren't found, that means we >> don't have any usable CRTCs, and the display pipeline is incomplete >> and useless. > > If some node set as available is not probed, then yes, it does, but > I'm not really sure how it's a problem. Quite the opposite actually. Actually the problem occurs when the TCON is _not_ available, but the other endpoints preceding it are. >> The whole DRM display pipeline should only be registered and enabled >> if there are proper outputs available. > > Unless I've misunderstood what you're saying, we could have the > writeback for example that would just need the display engine. Yeah, I guess that complicates things... >> The debug message "Queued %d outputs on pipeline %d\n" is also telling. >> >> This patch makes the driver only count enabled TCON endpoints. If >> none are found, the DRM pipeline is not used. This avoids screwing >> up the simple framebuffer provided by the bootloader in cases where >> we aren't able to support the display with the DRM subsystem, due >> to lack of panel or bridge drivers, or just lack of progress. > > The framebuffer is removed only at bind time, which means that all the > drivers have probed already. Lack of progress isn't an issue here, > since the node simply won't be there, and we wouldn't have it in the > component lists. And lack of drivers shouldn't be an issue either, > since in order for bind to be called, all the drivers would have > gone through their probe. > > So I'm not really sure what it fixes. To recap, on sun6i I had enabled the display engine node by default in the dtsi, along with the backend and drc. The tcon is disabled by default, so it doesn't get added to the list of components. The available components get probed, binded, and simplefb gets pushed out. I suppose disabling the display engine by default would be better? At least simplefb still works. Regards ChenYu > Maxime > > -- > Maxime Ripard, Free Electrons > Embedded Linux and Kernel engineering > http://free-electrons.com
Hi, On Fri, Nov 18, 2016 at 10:22:40AM +0800, Chen-Yu Tsai wrote: > On Fri, Nov 18, 2016 at 3:02 AM, Maxime Ripard > <maxime.ripard@free-electrons.com> wrote: > > On Wed, Nov 16, 2016 at 05:37:31PM +0800, Chen-Yu Tsai wrote: > >> The sun4i DRM driver counts the number of endpoints it found and > >> registers the whole DRM pipeline if any endpoints are found. > >> > >> However, if the TCON and its child endpoints (LCD panels, TV encoder, > >> HDMI encoder, MIPI DSI encoder, etc.) aren't found, that means we > >> don't have any usable CRTCs, and the display pipeline is incomplete > >> and useless. > > > > If some node set as available is not probed, then yes, it does, but > > I'm not really sure how it's a problem. Quite the opposite actually. > > Actually the problem occurs when the TCON is _not_ available, but > the other endpoints preceding it are. By preceding, you mean the display engine or the HDMI or TV encoders? > >> The debug message "Queued %d outputs on pipeline %d\n" is also telling. > >> > >> This patch makes the driver only count enabled TCON endpoints. If > >> none are found, the DRM pipeline is not used. This avoids screwing > >> up the simple framebuffer provided by the bootloader in cases where > >> we aren't able to support the display with the DRM subsystem, due > >> to lack of panel or bridge drivers, or just lack of progress. > > > > The framebuffer is removed only at bind time, which means that all the > > drivers have probed already. Lack of progress isn't an issue here, > > since the node simply won't be there, and we wouldn't have it in the > > component lists. And lack of drivers shouldn't be an issue either, > > since in order for bind to be called, all the drivers would have > > gone through their probe. > > > > So I'm not really sure what it fixes. > > To recap, on sun6i I had enabled the display engine node by default > in the dtsi, along with the backend and drc. The tcon is disabled > by default, so it doesn't get added to the list of components. > The available components get probed, binded, and simplefb gets > pushed out. > > I suppose disabling the display engine by default would be better? > At least simplefb still works. Yep, that works for me. Maxime
On Tue, Nov 22, 2016 at 11:37 PM, Maxime Ripard <maxime.ripard@free-electrons.com> wrote: > Hi, > > On Fri, Nov 18, 2016 at 10:22:40AM +0800, Chen-Yu Tsai wrote: >> On Fri, Nov 18, 2016 at 3:02 AM, Maxime Ripard >> <maxime.ripard@free-electrons.com> wrote: >> > On Wed, Nov 16, 2016 at 05:37:31PM +0800, Chen-Yu Tsai wrote: >> >> The sun4i DRM driver counts the number of endpoints it found and >> >> registers the whole DRM pipeline if any endpoints are found. >> >> >> >> However, if the TCON and its child endpoints (LCD panels, TV encoder, >> >> HDMI encoder, MIPI DSI encoder, etc.) aren't found, that means we >> >> don't have any usable CRTCs, and the display pipeline is incomplete >> >> and useless. >> > >> > If some node set as available is not probed, then yes, it does, but >> > I'm not really sure how it's a problem. Quite the opposite actually. >> >> Actually the problem occurs when the TCON is _not_ available, but >> the other endpoints preceding it are. > > By preceding, you mean the display engine or the HDMI or TV encoders? The display engine. >> >> The debug message "Queued %d outputs on pipeline %d\n" is also telling. >> >> >> >> This patch makes the driver only count enabled TCON endpoints. If >> >> none are found, the DRM pipeline is not used. This avoids screwing >> >> up the simple framebuffer provided by the bootloader in cases where >> >> we aren't able to support the display with the DRM subsystem, due >> >> to lack of panel or bridge drivers, or just lack of progress. >> > >> > The framebuffer is removed only at bind time, which means that all the >> > drivers have probed already. Lack of progress isn't an issue here, >> > since the node simply won't be there, and we wouldn't have it in the >> > component lists. And lack of drivers shouldn't be an issue either, >> > since in order for bind to be called, all the drivers would have >> > gone through their probe. >> > >> > So I'm not really sure what it fixes. >> >> To recap, on sun6i I had enabled the display engine node by default >> in the dtsi, along with the backend and drc. The tcon is disabled >> by default, so it doesn't get added to the list of components. >> The available components get probed, binded, and simplefb gets >> pushed out. >> >> I suppose disabling the display engine by default would be better? >> At least simplefb still works. > > Yep, that works for me. OK. I'll send out a patch. ChenYu
diff --git a/drivers/gpu/drm/sun4i/sun4i_drv.c b/drivers/gpu/drm/sun4i/sun4i_drv.c index c3b21865443e..3603f34901b6 100644 --- a/drivers/gpu/drm/sun4i/sun4i_drv.c +++ b/drivers/gpu/drm/sun4i/sun4i_drv.c @@ -243,9 +243,12 @@ static int sun4i_drv_add_endpoints(struct device *dev, DRM_DEBUG_DRIVER("Adding component %s\n", of_node_full_name(node)); component_match_add(dev, match, compare_of, node); - count++; } + /* Only count the tcon as an output */ + if (sun4i_drv_node_is_tcon(node)) + count++; + /* Inputs are listed first, then outputs */ port = of_graph_get_port_by_id(node, 1); if (!port) {
The sun4i DRM driver counts the number of endpoints it found and registers the whole DRM pipeline if any endpoints are found. However, if the TCON and its child endpoints (LCD panels, TV encoder, HDMI encoder, MIPI DSI encoder, etc.) aren't found, that means we don't have any usable CRTCs, and the display pipeline is incomplete and useless. The whole DRM display pipeline should only be registered and enabled if there are proper outputs available. The debug message "Queued %d outputs on pipeline %d\n" is also telling. This patch makes the driver only count enabled TCON endpoints. If none are found, the DRM pipeline is not used. This avoids screwing up the simple framebuffer provided by the bootloader in cases where we aren't able to support the display with the DRM subsystem, due to lack of panel or bridge drivers, or just lack of progress. Fixes: 9026e0d122ac ("drm: Add Allwinner A10 Display Engine support") Signed-off-by: Chen-Yu Tsai <wens@csie.org> --- Hi Maxime, This avoids DRM screwing up simplefb on my SinA31s, which does not have the display pipeline enabled in its dts file. But the display engine and backend are already enabled in the dtsi. I think this is a better and proper (for the driver) fix. The alternative would be to disable the display-engine node in the dts by default. Last time I asked you wanted to have them enabled by default? It may also be possible to push the check further down, and check against panel and encoder endpoints, but I think that complicates things. The TCON is a necessary part of the output. ChenYu --- drivers/gpu/drm/sun4i/sun4i_drv.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)