* [Question/Bug?] Why does the sysfs current_link_speed report a different value than pp_dpm_pcie
@ 2022-04-05 17:39 Maxime Schmitt
2022-05-09 2:47 ` Quan, Evan
0 siblings, 1 reply; 3+ messages in thread
From: Maxime Schmitt @ 2022-04-05 17:39 UTC (permalink / raw)
To: amd-gfx
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Hello,
On my system the sysfs file "current_link_speed" is reporting "16.0 GT/s
PCIe".
The GPU has support for PCIe gen 4 (AMD Radeon RX 6800 XT).
However neither the CPU (AMD Ryzen 7 1700X) nor the motherboard have
support for PCIe gen 4.
The file "pp_dpm_pcie" returns the following:
0: 2.5GT/s, x1 310Mhz
1: 8.0GT/s, x16 619Mhz *
Which is correct.
Is this the expected behavior?
I am asking because I recently added AMDGPU support to a monitoring tool I
maintain (nvtop) and I don't know where to get the information from.
Cheers,
Maxime
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^ permalink raw reply [flat|nested] 3+ messages in thread
* RE: [Question/Bug?] Why does the sysfs current_link_speed report a different value than pp_dpm_pcie
2022-04-05 17:39 [Question/Bug?] Why does the sysfs current_link_speed report a different value than pp_dpm_pcie Maxime Schmitt
@ 2022-05-09 2:47 ` Quan, Evan
2022-05-09 10:03 ` Lazar, Lijo
0 siblings, 1 reply; 3+ messages in thread
From: Quan, Evan @ 2022-05-09 2:47 UTC (permalink / raw)
To: Maxime Schmitt, amd-gfx, Deucher, Alexander
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[AMD Official Use Only - General]
From: amd-gfx <amd-gfx-bounces@lists.freedesktop.org> On Behalf Of Maxime Schmitt
Sent: Wednesday, April 6, 2022 1:40 AM
To: amd-gfx@lists.freedesktop.org
Subject: [Question/Bug?] Why does the sysfs current_link_speed report a different value than pp_dpm_pcie
Hello,
On my system the sysfs file "current_link_speed" is reporting "16.0 GT/s PCIe".
The GPU has support for PCIe gen 4 (AMD Radeon RX 6800 XT).
However neither the CPU (AMD Ryzen 7 1700X) nor the motherboard have support for PCIe gen 4.
The file "pp_dpm_pcie" returns the following:
0: 2.5GT/s, x1 310Mhz
1: 8.0GT/s, x16 619Mhz *
Which is correct.
Is this the expected behavior?
[Quan, Evan] "pp_dpm_pcie" is reporting the correct link speed. You can trust that.
While "current_link_speed" seems reporting the link speed the card is capable of. Not sure whether that fits design.
@Deucher, Alexander<mailto:Alexander.Deucher@amd.com> Any comments for the output of sysfs file "current_link_speed"?
BR
Evan
I am asking because I recently added AMDGPU support to a monitoring tool I maintain (nvtop) and I don't know where to get the information from.
Cheers,
Maxime
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Question/Bug?] Why does the sysfs current_link_speed report a different value than pp_dpm_pcie
2022-05-09 2:47 ` Quan, Evan
@ 2022-05-09 10:03 ` Lazar, Lijo
0 siblings, 0 replies; 3+ messages in thread
From: Lazar, Lijo @ 2022-05-09 10:03 UTC (permalink / raw)
To: Quan, Evan, Maxime Schmitt, amd-gfx, Deucher, Alexander, mike.zhou
+Mike
On 5/9/2022 8:17 AM, Quan, Evan wrote:
> [AMD Official Use Only - General]
>
> *From:* amd-gfx <amd-gfx-bounces@lists.freedesktop.org> *On Behalf Of
> *Maxime Schmitt
> *Sent:* Wednesday, April 6, 2022 1:40 AM
> *To:* amd-gfx@lists.freedesktop.org
> *Subject:* [Question/Bug?] Why does the sysfs current_link_speed report
> a different value than pp_dpm_pcie
>
> Hello,
>
> On my system the sysfs file "current_link_speed" is reporting "16.0 GT/s
> PCIe".
>
> The GPU has support for PCIe gen 4 (AMD Radeon RX 6800 XT).
>
> However neither the CPU (AMD Ryzen 7 1700X) nor the motherboard have
> support for PCIe gen 4.
>
> The file "pp_dpm_pcie" returns the following:
>
> 0: 2.5GT/s, x1 310Mhz
> 1: 8.0GT/s, x16 619Mhz *
>
> Which is correct.
>
> Is this the expected behavior?
>
> */[Quan, Evan] “pp_dpm_pcie” is reporting the correct link speed. You
> can trust that./*
>
> */While “current_link_speed” seems reporting the link speed the card is
> capable of. Not sure whether that fits design./*
>
> */@Deucher, Alexander <mailto:Alexander.Deucher@amd.com> Any comments
> for the output of sysfs file “current_link_speed”?/*
>
In our architecture, GFX endpoint is not directly connected to
CPU/Chipset PCIE. We have upstream/downstream bridges in between
CPU/Chipset <-> || US Port <-> DS Port <-> GFX EP||
The actual speed will be reflected in the US port connected to the
CPU/chipset port or pp_dpm_pcie node as it shows the speed reported by
power management firmware.
Thanks,
Lijo
> *//*
>
> */BR/*
>
> */Evan/*
>
> I am asking because I recently added AMDGPU support to a monitoring tool
> I maintain (nvtop) and I don't know where to get the information from.
>
> Cheers,
>
> Maxime
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-04-05 17:39 [Question/Bug?] Why does the sysfs current_link_speed report a different value than pp_dpm_pcie Maxime Schmitt
2022-05-09 2:47 ` Quan, Evan
2022-05-09 10:03 ` Lazar, Lijo
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