Some new variants require different firmwares.
Signed-off-by: Junwei Zhang <Jerry.Zhang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
New vega10 ids.
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Some new variants require updated firmware.
V2: add MODULE_FIRMWARE for new firmwares
Reviewed-by: Huang Rui <ray.huang@amd.com> (v1)
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Replace vcn_v1_0_stop with vcn_v1_0_set_powergating_state during suspend,
to keep adev->vcn.cur_state update. It will fix VCN S3 hung issue.
Signed-off-by: James Zhu <James.Zhu@amd.com>
Reviewed-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[Why]
New GCC warnings for stringop-truncation and stringop-overflow help
catch common misuse of strncpy. This patch suppresses these warnings
by fixing bugs identified by them.
[How]
Since the parameter passed for name in amdpgu_dm_create_common_mode has
no fixed length, if the string is >= DRM_DISPLAY_MODE_LEN then
mode->name will not be null-terminated.
The truncation in fill_audio_info won't actually occur (and the string
will be null-terminated since the buffer is initialized to zero), but
the warning can be suppressed by using the proper buffer size.
This patch fixes both issues by using the real size for the buffer and
making use of strscpy (which always terminates).
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
add protection code to avoid lower frequency trigger over drive.
Reviewed-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Tianci Yin <tianci.yin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
KIQ in VF’s init delayed by another VF’s reset,
which would cause late_init failed occasionally.
MAX_KIQ_REG_TRY enlarged from 20 to 80 would fix this issue.
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Wentao Lou <Wentao.Lou@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
For some case, no need to force SoftMin/Max settings for all DPMs.
It's OK to force on some specific DPM only.
Signed-off-by: Evan Quan <evan.quan@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
For display config change event only, pre-display config settings are
needed.
Signed-off-by: Evan Quan <evan.quan@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
New pptable upload through sysfs interface is supported.
Signed-off-by: Evan Quan <evan.quan@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Some power features rely on the driver loaded version so always
load the MC firmware from the driver even if the vbios loaded
a version already.
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Some variants require different MC firmware images.
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Some new variants require updated firmware.
Signed-off-by: Junwei Zhang <Jerry.Zhang@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Instead of delaying that to the first query. Otherwise we could try to use the
SDMA for VM updates before the IB tests are done.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Looks like it was missed when setting support was added.
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[Why]
More than 4x4K didn't lightup on Vega20 due to low dcfclk value.
Powerplay expects valid min requirement for dcfclk from DC.
[How]
Update min_dcfclock_khz based on min_engine_clock value.
v2: backport to 4.20 (Alex)
Reviewed-by: Hersen Wu <hersenxs.wu@amd.com>
Reviewed-by: Feifei Xu <Feifei.Xu@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Roman Li <Roman.Li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[Why]
If the "max bpc" isn't explicitly set in the atomic state then it
have a value of 0. This has the correct behavior of limiting a panel
to 8bpc in the case where the panel supports 8bpc. In the case of eDP
panels this isn't a true assumption - there are panels that can only
do 6bpc.
Banding occurs for these displays.
[How]
Initialize the max_bpc when the connector resets to 8bpc. Also carry
over the value when the state is duplicated.
Bugzilla: https://bugs.freedesktop.org/108825
Fixes: 307638884f72 ("drm/amd/display: Support amdgpu "max bpc" connector property")
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Driver shouldn't try to access any GFX registers until RLC is idle.
During the test, it took 12 seconds for RLC to clear the BUSY bit
in RLC_GPM_STAT register which is un-acceptable for driver.
As per RLC engineer, it would take RLC Ucode less than 10,000 GFXCLK
cycles to finish its critical section. In a lowest 300M enginer clock
setting(default from vbios), 50 us delay is enough.
This commit fix the hang when RLC introduce the work around for XGMI
which requires more cycles to setup more registers than normal
Signed-off-by: shaoyunl <shaoyun.liu@amd.com>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Don't bounce back to the root level for fragment processing, because
huge pages are not supported at that level. This is unlikely to happen
with the default VM size on Vega, but can be exposed by limiting the
VM size with the amdgpu.vm_size module parameter.
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Avoid potential integer overflows with left shift in huge-page mapping
code by casting the operand to uin64_t first.
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Path property is used for userspace to know what MST connector goes to what actual DRM DisplayPort connector, the tiling property is for tiling configurations. Not sure what else there is to figure out.
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Jerry (Fangzhi) Zuo <Jerry.Zuo@amd.com>
Cc: Stable <stable@vger.kernel.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
The change fixed huge delay in SST daisy chain and S3 soft hang
observed in 4.19 kernel rebase.
Regression point in drm:
drm/fb-helper: Eliminate the .best_encoder() usage
The aux sequence is altered due to the failure in
drm_connector_for_each_possible_encoder(). The failure is
caused by missing attached encoder in the process of adding
MST connector.
drm_dp_send_enum_path_resources() aux transaction is pushed after
mode probe, which causes conflict to drm_dp_mst_i2c_xfer(),
leading to the transaction timeout.
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Jerry (Fangzhi) Zuo <Jerry.Zuo@amd.com>
Cc: Stable <stable@vger.kernel.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Due to the register name and setting change of HDP
memory light sleep on Vega20,change accordingly in
the driver.
Signed-off-by: Kenneth Feng <kenneth.feng@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Reading the sysfs files pp_sclk_od and pp_mclk_od return the
percentage difference between the VBIOS-provided default
frequency and the current (possibly user-set) frequency in
the highest SCLK and MCLK DPM states, respectively.
Writing to these files provides an easy mechanism for
setting a higher-than-default maximum frequency. We
normally only allow values >= 0 to be written here.
However, with the addition of pp_od_clk_voltage, we now
allow users to set custom DPM tables. If they then set
the maximum DPM state to something less than the default,
later reads of pp_*_od should return a negative value.
The highest DPM state is now less than the VBIOS-provided
default, so the percentage is negative.
The math to calculate this was originally performed with
unsigned values, meaning reads that should return negative
values returned meaningless data. This patch corrects that
issue and normalizes how all of the calculations are done
across the various hwmgr types.
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Joseph Greathouse <Joseph.Greathouse@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Due to lack of MODULE_FIRMWARE() with hainan_mc.bin, the driver
doesn't work properly in initrd. Let's add it.
Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1116239
Fixes: 8eaf2b1faa ("drm/amdgpu: switch firmware path for SI parts")
Cc: <stable@vger.kernel.org>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Disable these features on Vega20 for now.
Signed-off-by: Evan Quan <evan.quan@amd.com>
Acked-by: Feifei Xu<Feifei.Xu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
On Vega20 and other pre-production GPUs, powerplay is not enabled yet.
Check for NULL pointers before calling pp_funcs function pointers.
Also affects Kaveri.
CC: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Tested-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
[Why]
Many panels support more than 8bpc but some modes are unavailable while
running at greater than 8bpc due to DP/HDMI bandwidth constraints.
Support for more than 8bpc was added recently in the driver but it
defaults to the maximum supported bpc - locking out these modes.
This should be a user configurable option such that the user can select
what bpc configuration they would like.
[How]
This patch adds support for getting and setting the amdgpu driver
specific "max bpc" property on the connector.
It also adds support for limiting the output bpc based on the property
value. The default limitation is the lowest value in the range, 8bpc.
This was the old value before the range was uncapped.
This patch should be updated/replaced later once common drm support
for max bpc lands.
Bugzilla: https://bugs.freedesktop.org/108542
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201585
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=200645
Fixes: e03fd3f300 ("drm/amd/display: Do not limit color depth to 8bpc")
v2: rebase on upstream (Alex)
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[Why]
Many panels support more than 8bpc but some modes are unavailable while
running at greater than 8bpc due to DP/HDMI bandwidth constraints.
Support for more than 8bpc was added recently in the driver but it
defaults to the maximum supported bpc - locking out these modes.
This should be a user configurable option such that the user can select
what bpc configuration they would like.
[How]
This patch introduces the "max bpc" amdgpu driver specific connector
property so the user can limit the maximum bpc. It ranges from 8 to 16.
This doesn't directly set the preferred bpc for the panel since it
follows Intel's existing driver conventions.
This proprety should be removed once common drm support for max bpc
lands.
v2: rebase on upstream (Alex)
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
We accidentially set the huge flag on the parent instead of the childs.
This caused some VM faults under memory pressure.
Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Tested-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
the clk value should be tranferred to MHz first and
then transfer to uint16. otherwise, the clock value
will be truncated.
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reported-by: Hersen Wu <hersenxs.wu@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
The bug limits the IH ring wptr address to 40bit. When the system memory
is bigger than 1TB, the bus address is more than 40bit, this causes the
interrupt cannot be handled and cleared correctly.
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
In XGMI configuration, the FB region covers vram region from peer
device, adjust system aperture to cover all of them
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: shaoyunl <shaoyun.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[why]
Removing connector reusage from DM to match the rest of the tree ended
up revealing an issue that was surprisingly subtle. The original amdgpu
code for DC that was submitted appears to have left a chunk in
dm_dp_create_fake_mst_encoder() that tries to find a "master encoder",
the likes of which isn't actually used or stored anywhere. It does so at
the wrong time as well by trying to access parts of the drm_connector
from the encoder init before it's actually been initialized. This
results in a NULL pointer deref on MST hotplugs:
[ 160.696613] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
[ 160.697234] PGD 0 P4D 0
[ 160.697814] Oops: 0010 [#1] SMP PTI
[ 160.698430] CPU: 2 PID: 64 Comm: kworker/2:1 Kdump: loaded Tainted: G O 4.19.0Lyude-Test+ #2
[ 160.699020] Hardware name: HP HP ZBook 15 G4/8275, BIOS P70 Ver. 01.22 05/17/2018
[ 160.699672] Workqueue: events_long drm_dp_mst_link_probe_work [drm_kms_helper]
[ 160.700322] RIP: 0010: (null)
[ 160.700920] Code: Bad RIP value.
[ 160.701541] RSP: 0018:ffffc9000029fc78 EFLAGS: 00010206
[ 160.702183] RAX: 0000000000000000 RBX: ffff8804440ed468 RCX: ffff8804440e9158
[ 160.702778] RDX: 0000000000000000 RSI: ffff8804556c5700 RDI: ffff8804440ed000
[ 160.703408] RBP: ffff880458e21800 R08: 0000000000000002 R09: 000000005fca0a25
[ 160.704002] R10: ffff88045a077a3d R11: ffff88045a077a3c R12: ffff8804440ed000
[ 160.704614] R13: ffff880458e21800 R14: ffff8804440e9000 R15: ffff8804440e9000
[ 160.705260] FS: 0000000000000000(0000) GS:ffff88045f280000(0000) knlGS:0000000000000000
[ 160.705854] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 160.706478] CR2: ffffffffffffffd6 CR3: 000000000200a001 CR4: 00000000003606e0
[ 160.707124] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 160.707724] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 160.708372] Call Trace:
[ 160.708998] ? dm_dp_add_mst_connector+0xed/0x1d0 [amdgpu]
[ 160.709625] ? drm_dp_add_port+0x2fa/0x470 [drm_kms_helper]
[ 160.710284] ? wake_up_q+0x54/0x70
[ 160.710877] ? __mutex_unlock_slowpath.isra.18+0xb3/0x110
[ 160.711512] ? drm_dp_dpcd_access+0xe7/0x110 [drm_kms_helper]
[ 160.712161] ? drm_dp_send_link_address+0x155/0x1e0 [drm_kms_helper]
[ 160.712762] ? drm_dp_check_and_send_link_address+0xa3/0xd0 [drm_kms_helper]
[ 160.713408] ? drm_dp_mst_link_probe_work+0x4b/0x80 [drm_kms_helper]
[ 160.714013] ? process_one_work+0x1a1/0x3a0
[ 160.714667] ? worker_thread+0x30/0x380
[ 160.715326] ? wq_update_unbound_numa+0x10/0x10
[ 160.715939] ? kthread+0x112/0x130
[ 160.716591] ? kthread_create_worker_on_cpu+0x70/0x70
[ 160.717262] ? ret_from_fork+0x35/0x40
[ 160.717886] Modules linked in: amdgpu(O) vfat fat snd_hda_codec_generic joydev i915 chash gpu_sched ttm i2c_algo_bit drm_kms_helper snd_hda_codec_hdmi hp_wmi syscopyarea iTCO_wdt sysfillrect sparse_keymap sysimgblt fb_sys_fops snd_hda_intel usbhid wmi_bmof drm snd_hda_codec btusb snd_hda_core intel_rapl btrtl x86_pkg_temp_thermal btbcm btintel coretemp snd_pcm crc32_pclmul bluetooth psmouse snd_timer snd pcspkr i2c_i801 mei_me i2c_core soundcore mei tpm_tis wmi tpm_tis_core hp_accel ecdh_generic lis3lv02d tpm video rfkill acpi_pad input_polldev hp_wireless pcc_cpufreq crc32c_intel serio_raw tg3 xhci_pci xhci_hcd [last unloaded: amdgpu]
[ 160.720141] CR2: 0000000000000000
Somehow the connector reusage DM was using for MST connectors managed to
paper over this issue entirely; hence why this was never caught until
now.
[how]
Since this code isn't used anywhere and seems useless anyway, we can
just drop it entirely. This appears to fix the issue on my HP ZBook with
an AMD WX4150.
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[why]
It is not safe to keep existing connector while entire topology
has been removed. Could lead potential impact to uapi.
Entirely unregister all the connectors on the topology,
and use a new set of connectors when the topology is plugged back
on.
[How]
Remove the drm connector entirely each time when the
corresponding MST topology is gone.
When hotunplug a connector (e.g., DP2)
1. Remove connector from userspace.
2. Drop it's reference.
When hotplug back on:
1. Detect new topology, and create new connectors.
2. Notify userspace with sysfs hotplug event.
3. Reprobe new connectors, and reassign CRTC from old (e.g., DP2)
to new (e.g., DP3) connector.
Signed-off-by: Jerry (Fangzhi) Zuo <Jerry.Zuo@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[why]
It is not correct to touch aconnector within atomic_check.
[How]
It was added as workaround before, and no longer needed.
Signed-off-by: Jerry (Fangzhi) Zuo <Jerry.Zuo@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
With UCLK DPM enabled, slow switching is not supported any more.
Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Feifei Xu <Feifei.Xu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Otherwise big gap between these two clocks may causes
some hangs.
Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Feifei Xu <Feifei.Xu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Causes a black screen on a Stoney laptop.
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=108577
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Set the dc_config properly when the option is enabled.
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Add FBC to the list of features that can be enabled from the DM.
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Similar to ppfeaturemask. Allows you to selectively enable/disable
DC features.
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
The value is dependent on whether fbc is available.
v2: only check if num_pipes is valid
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[Why]
drm_plane_cleanup does not free the plane.
[How]
Call drm_primary_helper_destroy which will also free the plane.
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
RETIMER_REDRIVER_INFO shows the buffer as a decimal value with a '0x'
prefix, which is somewhat misleading.
Fix it to print hexadecimal, as was intended.
Fixes: 2f14bc89("drm/amd/display: add retimer log for HWQ tuning use.")
Cc: Charlene Liu <charlene.liu@amd.com>
Cc: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Reviewed-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This reverts commit 0cafc82fae.
This breaks some apps that assume 0 is minimum brightness.
Revert for 4.20. This is fixed properly for drm-next/4.21 in:
"drm/amd: Don't fail on backlight = 0"
However, that patch depends on more extensive changes to the
backlight interface which are too invasive for -fixes.
Fixes: Bugzilla: https://bugs.freedesktop.org/108668
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
