* [Intel-gfx] How to fix screen resolution detection?
@ 2021-12-17 16:19 Alan Stern
2021-12-18 21:37 ` Alan Stern
2021-12-20 10:14 ` [Intel-gfx] " Jani Nikula
0 siblings, 2 replies; 5+ messages in thread
From: Alan Stern @ 2021-12-17 16:19 UTC (permalink / raw)
To: Jani Nikula, Joonas Lahtinen, Rodrigo Vivi; +Cc: intel-gfx
The screen resolution on my laptop is not reported accurately. Here's
an extract from the output of xdpyinfo:
screen #0:
dimensions: 3200x1800 pixels (847x476 millimeters)
resolution: 96x96 dots per inch
The number of pixels is correct, but the size and resolution values
smack of a bogus default. The actual width of the screen (determined
with a tape measure) is about 11.5 inches (291 mm), which yields a
resolution of 280 dots per inch (11 dots per mm), approximately.
Most definitely _not_ 96 dpi.
Presumably X gets the size/resolution information from Wayland, which
gets it from the kernel, which gets it from the firmware. So the kernel
driver is the logical place to start in figuring where things are going
wrong. The laptop uses i915; here are the relevant lines from the
kernel log:
[ 0.000000] Linux version 5.14.9-200.fc34.x86_64 (mockbuild@bkernel02.iad2.fedoraproject.org) (gcc (GCC) 11.2.1 20210728 (Red Hat 11.2.1-1), GNU ld version 2.35.2-5.fc34) #1 SMP Thu Sep 30 11:55:35 UTC 2021
[ 0.463895] efifb: probing for efifb
[ 0.463913] efifb: framebuffer at 0xe0000000, using 22500k, total 22500k
[ 0.463916] efifb: mode is 3200x1800x32, linelength=12800, pages=1
[ 0.463919] efifb: scrolling: redraw
[ 0.463920] efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0
[ 0.464028] Console: switching to colour frame buffer device 400x112
[ 0.474894] fb0: EFI VGA frame buffer device
[ 2.888858] fb0: switching to inteldrmfb from EFI VGA
[ 2.891260] Console: switching to colour dummy device 80x25
[ 2.891318] i915 0000:00:02.0: vgaarb: deactivate vga console
[ 2.902665] i915 0000:00:02.0: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=io+mem:owns=io+mem
[ 2.904833] i915 0000:00:02.0: [drm] Finished loading DMC firmware i915/skl_dmc_ver1_27.bin (v1.27)
[ 2.947359] [drm] Initialized i915 1.6.0 20201103 for 0000:00:02.0 on minor 0
[ 2.949468] ACPI: video: Video Device [GFX0] (multi-head: yes rom: no post: no)
[ 2.949803] input: Video Bus as /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/LNXVIDEO:00/input/input9
[ 2.964371] fbcon: i915 (fb0) is primary device
[ 2.979854] Console: switching to colour frame buffer device 400x112
[ 3.012355] i915 0000:00:02.0: [drm] fb0: i915 frame buffer device
Now, I know nothing about the kernel's graphics subsystems. How can I
find out what size/resolution information i915 is getting and passing to
Wayland? If it's wrong, how can I fix it?
Thanks,
Alan Stern
^ permalink raw reply [flat|nested] 5+ messages in thread
* How to fix screen resolution detection?
2021-12-17 16:19 [Intel-gfx] How to fix screen resolution detection? Alan Stern
@ 2021-12-18 21:37 ` Alan Stern
2021-12-20 10:14 ` [Intel-gfx] " Jani Nikula
1 sibling, 0 replies; 5+ messages in thread
From: Alan Stern @ 2021-12-18 21:37 UTC (permalink / raw)
To: David Airlie, Daniel Vetter; +Cc: dri-devel, Kernel development list
The screen resolution on my laptop is not reported accurately. Here's
an extract from the output of xdpyinfo:
screen #0:
dimensions: 3200x1800 pixels (847x476 millimeters)
resolution: 96x96 dots per inch
The number of pixels is correct, but the size and resolution values
smack of a bogus default. The actual width of the screen (determined
with a tape measure) is about 11.5 inches (291 mm), which yields a
resolution of 280 dots per inch (11 dots per mm), approximately.
Most definitely _not_ 96 dpi.
Presumably X gets the size/resolution information from Wayland, which
gets it from the kernel, which gets it from the firmware. So the kernel
driver is the logical place to start in figuring where things are going
wrong. The laptop uses i915; here are the relevant lines from the
kernel log:
[ 0.000000] Linux version 5.14.9-200.fc34.x86_64 (mockbuild@bkernel02.iad2.fedoraproject.org) (gcc (GCC) 11.2.1 20210728 (Red Hat 11.2.1-1), GNU ld version 2.35.2-5.fc34) #1 SMP Thu Sep 30 11:55:35 UTC 2021
[ 0.463895] efifb: probing for efifb
[ 0.463913] efifb: framebuffer at 0xe0000000, using 22500k, total 22500k
[ 0.463916] efifb: mode is 3200x1800x32, linelength=12800, pages=1
[ 0.463919] efifb: scrolling: redraw
[ 0.463920] efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0
[ 0.464028] Console: switching to colour frame buffer device 400x112
[ 0.474894] fb0: EFI VGA frame buffer device
[ 2.888858] fb0: switching to inteldrmfb from EFI VGA
[ 2.891260] Console: switching to colour dummy device 80x25
[ 2.891318] i915 0000:00:02.0: vgaarb: deactivate vga console
[ 2.902665] i915 0000:00:02.0: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=io+mem:owns=io+mem
[ 2.904833] i915 0000:00:02.0: [drm] Finished loading DMC firmware i915/skl_dmc_ver1_27.bin (v1.27)
[ 2.947359] [drm] Initialized i915 1.6.0 20201103 for 0000:00:02.0 on minor 0
[ 2.949468] ACPI: video: Video Device [GFX0] (multi-head: yes rom: no post: no)
[ 2.949803] input: Video Bus as /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/LNXVIDEO:00/input/input9
[ 2.964371] fbcon: i915 (fb0) is primary device
[ 2.979854] Console: switching to colour frame buffer device 400x112
[ 3.012355] i915 0000:00:02.0: [drm] fb0: i915 frame buffer device
Now, I know nothing about the kernel's graphics subsystems. How can I
find out what size/resolution information i915 is getting and passing to
Wayland? If it's wrong, how can I fix it?
Thanks,
Alan Stern
^ permalink raw reply [flat|nested] 5+ messages in thread
* How to fix screen resolution detection?
@ 2021-12-18 21:37 ` Alan Stern
0 siblings, 0 replies; 5+ messages in thread
From: Alan Stern @ 2021-12-18 21:37 UTC (permalink / raw)
To: David Airlie, Daniel Vetter; +Cc: Kernel development list, dri-devel
The screen resolution on my laptop is not reported accurately. Here's
an extract from the output of xdpyinfo:
screen #0:
dimensions: 3200x1800 pixels (847x476 millimeters)
resolution: 96x96 dots per inch
The number of pixels is correct, but the size and resolution values
smack of a bogus default. The actual width of the screen (determined
with a tape measure) is about 11.5 inches (291 mm), which yields a
resolution of 280 dots per inch (11 dots per mm), approximately.
Most definitely _not_ 96 dpi.
Presumably X gets the size/resolution information from Wayland, which
gets it from the kernel, which gets it from the firmware. So the kernel
driver is the logical place to start in figuring where things are going
wrong. The laptop uses i915; here are the relevant lines from the
kernel log:
[ 0.000000] Linux version 5.14.9-200.fc34.x86_64 (mockbuild@bkernel02.iad2.fedoraproject.org) (gcc (GCC) 11.2.1 20210728 (Red Hat 11.2.1-1), GNU ld version 2.35.2-5.fc34) #1 SMP Thu Sep 30 11:55:35 UTC 2021
[ 0.463895] efifb: probing for efifb
[ 0.463913] efifb: framebuffer at 0xe0000000, using 22500k, total 22500k
[ 0.463916] efifb: mode is 3200x1800x32, linelength=12800, pages=1
[ 0.463919] efifb: scrolling: redraw
[ 0.463920] efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0
[ 0.464028] Console: switching to colour frame buffer device 400x112
[ 0.474894] fb0: EFI VGA frame buffer device
[ 2.888858] fb0: switching to inteldrmfb from EFI VGA
[ 2.891260] Console: switching to colour dummy device 80x25
[ 2.891318] i915 0000:00:02.0: vgaarb: deactivate vga console
[ 2.902665] i915 0000:00:02.0: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=io+mem:owns=io+mem
[ 2.904833] i915 0000:00:02.0: [drm] Finished loading DMC firmware i915/skl_dmc_ver1_27.bin (v1.27)
[ 2.947359] [drm] Initialized i915 1.6.0 20201103 for 0000:00:02.0 on minor 0
[ 2.949468] ACPI: video: Video Device [GFX0] (multi-head: yes rom: no post: no)
[ 2.949803] input: Video Bus as /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/LNXVIDEO:00/input/input9
[ 2.964371] fbcon: i915 (fb0) is primary device
[ 2.979854] Console: switching to colour frame buffer device 400x112
[ 3.012355] i915 0000:00:02.0: [drm] fb0: i915 frame buffer device
Now, I know nothing about the kernel's graphics subsystems. How can I
find out what size/resolution information i915 is getting and passing to
Wayland? If it's wrong, how can I fix it?
Thanks,
Alan Stern
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Intel-gfx] How to fix screen resolution detection?
2021-12-17 16:19 [Intel-gfx] How to fix screen resolution detection? Alan Stern
2021-12-18 21:37 ` Alan Stern
@ 2021-12-20 10:14 ` Jani Nikula
2021-12-20 21:50 ` Alan Stern
1 sibling, 1 reply; 5+ messages in thread
From: Jani Nikula @ 2021-12-20 10:14 UTC (permalink / raw)
To: Alan Stern, Joonas Lahtinen, Rodrigo Vivi; +Cc: intel-gfx
On Fri, 17 Dec 2021, Alan Stern <stern@rowland.harvard.edu> wrote:
> The screen resolution on my laptop is not reported accurately. Here's
> an extract from the output of xdpyinfo:
>
> screen #0:
> dimensions: 3200x1800 pixels (847x476 millimeters)
> resolution: 96x96 dots per inch
>
> The number of pixels is correct, but the size and resolution values
> smack of a bogus default. The actual width of the screen (determined
> with a tape measure) is about 11.5 inches (291 mm), which yields a
> resolution of 280 dots per inch (11 dots per mm), approximately.
> Most definitely _not_ 96 dpi.
>
> Presumably X gets the size/resolution information from Wayland, which
> gets it from the kernel, which gets it from the firmware. So the kernel
> driver is the logical place to start in figuring where things are going
> wrong. The laptop uses i915; here are the relevant lines from the
> kernel log:
>
> [ 0.000000] Linux version 5.14.9-200.fc34.x86_64 (mockbuild@bkernel02.iad2.fedoraproject.org) (gcc (GCC) 11.2.1 20210728 (Red Hat 11.2.1-1), GNU ld version 2.35.2-5.fc34) #1 SMP Thu Sep 30 11:55:35 UTC 2021
>
> [ 0.463895] efifb: probing for efifb
> [ 0.463913] efifb: framebuffer at 0xe0000000, using 22500k, total 22500k
> [ 0.463916] efifb: mode is 3200x1800x32, linelength=12800, pages=1
> [ 0.463919] efifb: scrolling: redraw
> [ 0.463920] efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0
> [ 0.464028] Console: switching to colour frame buffer device 400x112
> [ 0.474894] fb0: EFI VGA frame buffer device
>
> [ 2.888858] fb0: switching to inteldrmfb from EFI VGA
> [ 2.891260] Console: switching to colour dummy device 80x25
> [ 2.891318] i915 0000:00:02.0: vgaarb: deactivate vga console
> [ 2.902665] i915 0000:00:02.0: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=io+mem:owns=io+mem
> [ 2.904833] i915 0000:00:02.0: [drm] Finished loading DMC firmware i915/skl_dmc_ver1_27.bin (v1.27)
> [ 2.947359] [drm] Initialized i915 1.6.0 20201103 for 0000:00:02.0 on minor 0
> [ 2.949468] ACPI: video: Video Device [GFX0] (multi-head: yes rom: no post: no)
> [ 2.949803] input: Video Bus as /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/LNXVIDEO:00/input/input9
> [ 2.964371] fbcon: i915 (fb0) is primary device
> [ 2.979854] Console: switching to colour frame buffer device 400x112
> [ 3.012355] i915 0000:00:02.0: [drm] fb0: i915 frame buffer device
>
> Now, I know nothing about the kernel's graphics subsystems. How can I
> find out what size/resolution information i915 is getting and passing to
> Wayland? If it's wrong, how can I fix it?
I could be wrong, but I think userspace figures the dimensions from the
EDID itself, not through a kernel API.
I actually get slightly different results from xrandr, xdpyinfo, and
edid-decode on the EDID. What does edid-decode tell you for the
dimensions? For me it's 'edid-decode /sys/class/drm/card0-DP-3/edid' but
replace the subdir with your info.
xdpyinfo also gives me 96x96 dpi, probably bogus.
BR,
Jani.
--
Jani Nikula, Intel Open Source Graphics Center
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Intel-gfx] How to fix screen resolution detection?
2021-12-20 10:14 ` [Intel-gfx] " Jani Nikula
@ 2021-12-20 21:50 ` Alan Stern
0 siblings, 0 replies; 5+ messages in thread
From: Alan Stern @ 2021-12-20 21:50 UTC (permalink / raw)
To: Jani Nikula; +Cc: intel-gfx
On Mon, Dec 20, 2021 at 12:14:48PM +0200, Jani Nikula wrote:
> On Fri, 17 Dec 2021, Alan Stern <stern@rowland.harvard.edu> wrote:
> > The screen resolution on my laptop is not reported accurately. Here's
> > an extract from the output of xdpyinfo:
> >
> > screen #0:
> > dimensions: 3200x1800 pixels (847x476 millimeters)
> > resolution: 96x96 dots per inch
> >
> > The number of pixels is correct, but the size and resolution values
> > smack of a bogus default. The actual width of the screen (determined
> > with a tape measure) is about 11.5 inches (291 mm), which yields a
> > resolution of 280 dots per inch (11 dots per mm), approximately.
> > Most definitely _not_ 96 dpi.
> >
> > Presumably X gets the size/resolution information from Wayland, which
> > gets it from the kernel, which gets it from the firmware. So the kernel
> > driver is the logical place to start in figuring where things are going
> > wrong. The laptop uses i915; here are the relevant lines from the
> > kernel log:
> >
> > [ 0.000000] Linux version 5.14.9-200.fc34.x86_64 (mockbuild@bkernel02.iad2.fedoraproject.org) (gcc (GCC) 11.2.1 20210728 (Red Hat 11.2.1-1), GNU ld version 2.35.2-5.fc34) #1 SMP Thu Sep 30 11:55:35 UTC 2021
> >
> > [ 0.463895] efifb: probing for efifb
> > [ 0.463913] efifb: framebuffer at 0xe0000000, using 22500k, total 22500k
> > [ 0.463916] efifb: mode is 3200x1800x32, linelength=12800, pages=1
> > [ 0.463919] efifb: scrolling: redraw
> > [ 0.463920] efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0
> > [ 0.464028] Console: switching to colour frame buffer device 400x112
> > [ 0.474894] fb0: EFI VGA frame buffer device
> >
> > [ 2.888858] fb0: switching to inteldrmfb from EFI VGA
> > [ 2.891260] Console: switching to colour dummy device 80x25
> > [ 2.891318] i915 0000:00:02.0: vgaarb: deactivate vga console
> > [ 2.902665] i915 0000:00:02.0: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=io+mem:owns=io+mem
> > [ 2.904833] i915 0000:00:02.0: [drm] Finished loading DMC firmware i915/skl_dmc_ver1_27.bin (v1.27)
> > [ 2.947359] [drm] Initialized i915 1.6.0 20201103 for 0000:00:02.0 on minor 0
> > [ 2.949468] ACPI: video: Video Device [GFX0] (multi-head: yes rom: no post: no)
> > [ 2.949803] input: Video Bus as /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/LNXVIDEO:00/input/input9
> > [ 2.964371] fbcon: i915 (fb0) is primary device
> > [ 2.979854] Console: switching to colour frame buffer device 400x112
> > [ 3.012355] i915 0000:00:02.0: [drm] fb0: i915 frame buffer device
> >
> > Now, I know nothing about the kernel's graphics subsystems. How can I
> > find out what size/resolution information i915 is getting and passing to
> > Wayland? If it's wrong, how can I fix it?
>
> I could be wrong, but I think userspace figures the dimensions from the
> EDID itself, not through a kernel API.
>
> I actually get slightly different results from xrandr, xdpyinfo, and
> edid-decode on the EDID. What does edid-decode tell you for the
> dimensions? For me it's 'edid-decode /sys/class/drm/card0-DP-3/edid' but
> replace the subdir with your info.
>
> xdpyinfo also gives me 96x96 dpi, probably bogus.
Here's the result:
# edid-decode -s /sys/class/drm/card0-eDP-1/edid
Block 0, Base EDID:
EDID Structure Version & Revision: 1.4
Vendor & Product Identification:
Manufacturer: SDC
Model: 22602
Made in: 2015
Basic Display Parameters & Features:
Digital display
Bits per primary color channel: 8
DisplayPort interface
Maximum image size: 29 cm x 17 cm
Gamma: 2.20
DPMS levels: Standby Suspend Off
Supported color formats: RGB 4:4:4, YCrCb 4:4:4
First detailed timing includes the native pixel format and preferred refresh rate
Color Characteristics:
Red : 0.6396, 0.3300
Green: 0.2998, 0.5996
Blue : 0.1503, 0.0595
White: 0.3134, 0.3291
Established Timings I & II: none
Standard Timings: none
Detailed Timing Descriptors:
DTD 1: 3200x1800 60.000 Hz 16:9 108.960 kHz 361.310 MHz (293 mm x 165 mm)
Hfront 48 Hsync 32 Hback 36 Hpol N
Vfront 2 Vsync 5 Vback 9 Vpol N
Manufacturer-Specified Display Descriptor (0x0f): 00 0f 00 00 00 00 00 00 00 00 00 37 82 05 46 00 '...........7..F.'
Alphanumeric Data String: 'SAMSUNG'
Alphanumeric Data String: '133YL02-C02'
Checksum: 0x41
The 293 mm x 165 mm values listed on the "DTD 1" line seem right.
Maybe a little larger than the actual size but close enough.
So it looks as though the problem must lie in userspace (Wayland or X).
Any advice on whom I should ask next?
Alan Stern
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2021-12-20 21:50 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2021-12-17 16:19 [Intel-gfx] How to fix screen resolution detection? Alan Stern
2021-12-18 21:37 ` Alan Stern
2021-12-18 21:37 ` Alan Stern
2021-12-20 10:14 ` [Intel-gfx] " Jani Nikula
2021-12-20 21:50 ` Alan Stern
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