drm/i915/gem: Downgrade stolen lmem setup warning

In the case where lmem_size < dsm_base, hardware is reporting that
stolen lmem is unusable.  In this case, instead of throwing a warning,
we can continue execution as normal by disabling stolen LMEM support.
For example, this change will allow the following error report from
ATS-M to no longer apply:

<6> [144.859887] pcieport 0000:4b:00.0: bridge window [mem 0xb1000000-0xb11fffff]
<6> [144.859900] pcieport 0000:4b:00.0: bridge window [mem 0x3bbc00000000-0x3bbc17ffffff 64bit pref]
<6> [144.859917] pcieport 0000:4c:01.0: PCI bridge to [bus 4d-4e]
<6> [144.859932] pcieport 0000:4c:01.0: bridge window [mem 0xb1000000-0xb11fffff]
<6> [144.859945] pcieport 0000:4c:01.0: bridge window [mem 0x3bbc00000000-0x3bbc17ffffff 64bit pref]
<6> [144.859984] i915 0000:4d:00.0: [drm] BAR2 resized to 256M
<6> [144.860640] i915 0000:4d:00.0: [drm] Using a reduced BAR size of 256MiB. Consider enabling 'Resizable BAR' or similar, if available in the BIOS.
<4> [144.860719] -----------[ cut here ]-----------
<4> [144.860727] WARNING: CPU: 17 PID: 1815 at drivers/gpu/drm/i915/gem/i915_gem_stolen.c:939 i915_gem_stolen_lmem_setup+0x38c/0x430 [i915]
<4> [144.861430] Modules linked in: i915 snd_intel_dspcfg snd_hda_codec snd_hwdep snd_hda_core snd_pcm vgem drm_shmem_helper prime_numbers i2c_algo_bit ttm video drm_display_helper drm_buddy fuse x86_pkg_temp_thermal coretemp kvm_intel kvm ixgbe mdio irqbypass ptp crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pps_core i2c_i801 mei_me i2c_smbus mei wmi acpi_power_meter [last unloaded: i915]
<4> [144.861611] CPU: 17 PID: 1815 Comm: i915_module_loa Tainted: G U 6.8.0-rc5-drmtip_1515-g78f49af27723+ #1
<4> [144.861624] Hardware name: Intel Corporation WHITLEY/WHITLEY, BIOS SE5C6200.86B.0020.P41.2109300305 09/30/2021
<4> [144.861632] RIP: 0010:i915_gem_stolen_lmem_setup+0x38c/0x430 [i915]
<4> [144.862287] Code: ff 41 c1 e4 05 e9 ac fe ff ff 4d 63 e4 48 89 ef 48 85 ed 74 04 48 8b 7d 08 48 c7 c6 10 a3 7b a0 e8 e9 90 43 e1 e9 ee fd ff ff <0f> 0b 49 c7 c4 ed ff ff ff e9 e0 fd ff ff 0f b7 d2 48 c7 c6 00 d9
<4> [144.862299] RSP: 0018:ffffc90005607980 EFLAGS: 00010207
<4> [144.862315] RAX: fffffffffff00000 RBX: 0000000000000003 RCX: 0000000000000000

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10833Suggested-by: Chris Wilson <chris.p.wilson@linux.intel.com>
Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240422135959.4127003-1-jonathan.cavitt@intel.com

drivers/gpu/drm/i915/gem/i915_gem_stolen.c

@@ -936,8 +936,12 @@ i915_gem_stolen_lmem_setup(struct drm_i915_private *i915, u16 type,
 	} else {
 		/* Use DSM base address instead for stolen memory */
 		dsm_base = intel_uncore_read64(uncore, GEN6_DSMBASE) & GEN11_BDSM_MASK;
-		if (WARN_ON(lmem_size < dsm_base))
-			return ERR_PTR(-ENODEV);
+		if (lmem_size < dsm_base) {
+			drm_dbg(&i915->drm,
+				"Disabling stolen memory support due to OOB placement: lmem_size = %lli vs dsm_base = %lli\n",
+				lmem_size, dsm_base);
+			return 0;
+		}
 		dsm_size = ALIGN_DOWN(lmem_size - dsm_base, SZ_1M);
 	}