On 11/08/13 20:42, Dave Airlie wrote:
On Sun, Aug 11, 2013 at 2:41 PM, Tony Prisk <linux@xxxxxxxxxxxxxxx> wrote:
I am working on the HDMI driver for the i.MX6 as part of the larger DRM
driver written by Sascha Hauer and need a little advice. I seem to be
missing one important part of the subsystem that I haven't been able to
resolve.
fbcon is limited by boot sizes as at least with dynamic memory
management and how fbdev works resizing the allocation is nearly
impossible to do race free, since fbdev will hand out mmaps to
userspace and that stops you from ever moving anything once the device
is open.
But this is only for the fbdev emulation, a real kms application
should be able to use a larger size no problems.
Dave.
It seems to be worse than just a fbcon issue as far as I can tell.
I am making an assumption, but I believe
'/sys/class/drm/card0-HDMI-A-1/modes' should list all the supported
modes of the connector (regardless of fbcon).
Using 'cat /sys/class/drm/card0-HDMI-A-1/modes', it appears the
supported modes are being limited by fbcon
1) HDMI Cable connected at bootup (fb @ 1920x1080)
cat /sys/class/drm/card0-HDMI-A-1/modes
1920x1080
1280x720
1280x720
720x576
720x480
640x480
2) HDMI Cable NOT connected at bootup (fb @ 1024x768), cable is then
connected after userspace has started (still in console)
cat /sys/class/drm/card0-HDMI-A-1/modes
720x576
720x480
640x480
Following back through the source:
static struct drm_connector_funcs imx_hdmi_connector_funcs = {
.fill_modes = drm_helper_probe_single_connector_modes,
...
};
static struct drm_connector_helper_funcs imx_hdmi_connector_helper_funcs = {
.get_modes = imx_hdmi_connector_get_modes,
.mode_valid = imx_hdmi_connector_mode_valid,
...
};
It appears that only drm_helper_probe_single_connector_modes() calls
.get_modes() and .mode_valid()
.fill_modes() is called from drm_fb_helper_probe_connector_modes(),
which is called from drm_fb_helper_hotplug_event()
drm_fb_helper_hotplug_event() sets max_width to fb_helper->fb->width,
and max_height to fb_helper->fb->height.
fb->width is 1024 if booted without the cable connected, hence the
clipping of the values.
Regards
Tony Prisk
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