From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 10DF2C433EF for ; Mon, 20 Dec 2021 21:50:28 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 5834310FA84; Mon, 20 Dec 2021 21:50:27 +0000 (UTC) Received: from netrider.rowland.org (netrider.rowland.org [192.131.102.5]) by gabe.freedesktop.org (Postfix) with SMTP id 42C6110FA84 for ; Mon, 20 Dec 2021 21:50:26 +0000 (UTC) Received: (qmail 921894 invoked by uid 1000); 20 Dec 2021 16:50:24 -0500 Date: Mon, 20 Dec 2021 16:50:24 -0500 From: Alan Stern To: Jani Nikula Message-ID: References: <87ee671t2f.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87ee671t2f.fsf@intel.com> Subject: Re: [Intel-gfx] How to fix screen resolution detection? X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: intel-gfx@lists.freedesktop.org Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Mon, Dec 20, 2021 at 12:14:48PM +0200, Jani Nikula wrote: > On Fri, 17 Dec 2021, Alan Stern 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