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echo 命令在手动执行时有效，但作为 bash 脚本插入时无效

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echo 命令在手动执行时有效，但作为 bash 脚本插入时无效

我正在使用 Ubuntu 19.04，并且使用 AMD RX460 连接到我的 LG LED 电视时，HDMI 上有声音噼啪作响。

这可能与 AMD GPU 驱动程序有关，因为我在 Windows 10 pro 上遇到了完全相同的问题。在 Windows 上，我使用 AMD Adrenaline GUI 来解决问题，方法是不让 GPU 进入 p-State 0（214 MHz，0.8v）。在那里，我将 p-State 1 设置为最小状态，并修改频率和电压以匹配 p-State 0。可能 p-State 0 应用了一些其他省电设置，这就是为什么为 p-state 1 设置相同的频率和电压会产生相同的噼啪声。

现在我尝试在 Ubuntu 19.04 上做同样的事情，但使用 amdgpu 驱动程序。我创建了文件 hdmi-audio-crack-fix 和 hdmi-audio-crack-fix.service，如下所示：

1- 将 hdmi-audio-crack-fix 放置在 /usr/bin 中，并具有适当的权限。

#!/bin/bash
# This simple script disables pstate 0 for amdgpu to fix audio crackling over hdmi.
# Then pstate 1 is modified to match pstate 0 voltage and frequency.
# Also a little bit of undervolting is introduced.
# Copy to /usr/bin/ and then copy .service file to /etc/systemd/system/

# Using Ubuntu echo located inside /bin instead of bash built-in echo
amdgpu_echo="/bin/echo"

# Change amdgpu dpm performance level to manual
$amdgpu_echo "manual" > /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/power_dpm_force_performance_level

# Disable pstate 0 as this is causing the crackling over hdmi
$amdgpu_echo "1 2 3 4 5 6 7" >  /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/pp_dpm_sclk
$amdgpu_echo "1 2 3 4 5 6 7" >  /sys/class/drm/card0/device/pp_dpm_sclk

# Now reduce pstate 1 clock to reduce temperature on idle
$amdgpu_echo "s 1 220 800" > /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/pp_od_clk_voltage

# Undervolting gpu for highest pstates
$amdgpu_echo "s 5 1138 992" > /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/pp_od_clk_voltage
$amdgpu_echo "s 6 1172 1005" > /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/pp_od_clk_voltage
$amdgpu_echo "s 7 1212 1050" > /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/pp_od_clk_voltage
# Now sync new core/voltage table with GPU
$amdgpu_echo 'c' > /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/pp_od_clk_voltage

2- 将 hdmi-audio-crack-fix.service 放在 /etc/systemd/system/ 内并执行sudo systemctl enable hdmi-audio-crack-fix.service。

[Unit]
Description=Temporary fix for amdgpu HDMI audio crackling

[Service]
Type=oneshot
ExecStart=/usr/bin/hdmi-audio-crack-fix

[Install]
WantedBy=multi-user.target

一切都按预期工作，但以下行似乎没有任何效果，并且 GPU 仍然进入 p-State 0：

$amdgpu_echo "1 2 3 4 5 6 7" >  /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/pp_dpm_sclk

或者

$amdgpu_echo "1 2 3 4 5 6 7" >  /sys/class/drm/card0/device/pp_dpm_sclk

问题是，当我使用以下命令通过终端手动执行此命令时，它可以正常工作：

sudo su -
echo "1 2 3 4 5 6 7" >  /sys/class/drm/card0/device/pp_dpm_sclk

更新：

这是服务状态的输出：

● hdmi-audio-crack-fix.service - Temporarly fix for amdgpu HDMI audio crackling
   Loaded: loaded (/etc/systemd/system/hdmi-audio-crack-fix.service; enabled; vendor preset: enabled)
   Active: inactive (dead) since Sat 2019-05-04 21:24:25 +0430; 4h 14min ago
 Main PID: 1004 (code=exited, status=0/SUCCESS)

May 04 21:24:24 Rivendell systemd[1]: Starting Temporarly fix for amdgpu HDMI audio crackling...
May 04 21:24:25 Rivendell systemd[1]: hdmi-audio-crack-fix.service: Succeeded.
May 04 21:24:25 Rivendell systemd[1]: Started Temporarly fix for amdgpu HDMI audio crackling.

答案1

好吧，我找到了问题，它与 bash 脚本无关。我说的无法产生 gpu 所需行为的命令实际上正在运行。

我不知道的是，每当 pp_od_clk_voltage 被修改时，pp_dpm_sclk 都会重置为默认值。因此，在修改 pp_od_clk_voltage 之前的任何更改都是无用的。

我只需要在执行与 pp_od_clk_voltage 相关的命令后执行与 pp_dpm_sclk 相关的命令即可。如果有人感兴趣的话，最终的工作脚本如下（AMD RX460）：

#!/bin/bash
# **************************************Info************************************* #
#                                         #
# This simple script disables p-State 0 for amdgpu: fix audio-crackling over hdmi.#
# Then p-State 1 is modified to match p-State 0 voltage and frequency.        #
# Also a little bit of undervolting is also introduced to keep gpu happy.     #
#                                         #
# *************************************README************************************ #
#                                         #
# Inside the directory containing hdmi-audio-crack-fix and .service files, run:   #
#                                         #
#   sudo cp hdmi-audio-crack-fix /usr/bin/                    #
#       sudo chmod 755 /usr/bin/hdmi-audio-crack-fix                  #
#   sudo cp hdmi-audio-crack-fix.service /etc/systemd/system/         #
#   sudo systemctl enable hdmi-audio-crack-fix.service            #
#                                         #
# Check if everything is working as intended:                     #
#       cat /sys/class/drm/card0/device/pp_od_clk_voltage             #
#       cat /sys/class/drm/card0/device/pp_dpm_sclk           #
#                                         #
# **************************************END************************************** #

# Change amdgpu dpm performance level to manual
echo "manual" > /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/power_dpm_force_performance_level

# Reduceing p-State 1 and 2 clock to reduce temperature on idle
echo "s 1 220 800" > /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/pp_od_clk_voltage
echo "s 2 620 810" > /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/pp_od_clk_voltage

# Undervolting gpu for the highest p-States: 5, 6, 7
echo "s 5 1138 992" > /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/pp_od_clk_voltage
echo "s 6 1172 1005" > /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/pp_od_clk_voltage
echo "s 7 1212 1050" > /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/pp_od_clk_voltage

# Now sync new core/voltage table with GPU
echo "c" > /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/pp_od_clk_voltage

# Finally, Disable pstate 0 as this is causing the crackling over hdmi
# This step should run after any modification to pp_od_clk_voltage, otherwise it gets reset.
echo "1 2 3 4 5 6 7" >  /sys/devices/pci0000:64/0000:64:00.0/0000:65:00.0/pp_dpm_sclk

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