linux-kernel - Re: [PATCH 1/2] PCI/ASPM: Store disabled ASPM states

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Message-ID: <4212dca6-233b-4d6c-0182-1e7912a05b3f@gmail.com>
Date:   Tue, 8 Dec 2020 18:11:09 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>, bhelgaas@...gle.com
Cc:     "Saheed O. Bolarinwa" <refactormyself@...il.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Chris Packham <chris.packham@...iedtelesis.co.nz>,
        Xiongfeng Wang <wangxiongfeng2@...wei.com>,
        Yicong Yang <yangyicong@...ilicon.com>,
        "open list:PCI SUBSYSTEM" <linux-pci@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] PCI/ASPM: Store disabled ASPM states

Am 08.12.2020 um 09:25 schrieb Kai-Heng Feng:
> If we use sysfs to disable L1 ASPM, then enable one L1 ASPM substate
> again, all other substates will also be enabled too:
> 
> link# grep . *
> clkpm:1
> l0s_aspm:1
> l1_1_aspm:1
> l1_1_pcipm:1
> l1_2_aspm:1
> l1_2_pcipm:1
> l1_aspm:1
> 
> link# echo 0 > l1_aspm
> 
> link# grep . *
> clkpm:1
> l0s_aspm:1
> l1_1_aspm:0
> l1_1_pcipm:0
> l1_2_aspm:0
> l1_2_pcipm:0
> l1_aspm:0
> 
> link# echo 1 > l1_2_aspm
> 
> link# grep . *
> clkpm:1
> l0s_aspm:1
> l1_1_aspm:1
> l1_1_pcipm:1
> l1_2_aspm:1
> l1_2_pcipm:1
> l1_aspm:1
> 
> This is because disabled ASPM states weren't saved, so enable any of the
> substate will also enable others.
> 
> So store the disabled ASPM states for consistency.
> 
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> ---
>  drivers/pci/pcie/aspm.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index ac0557a305af..2ea9fddadfad 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -658,6 +658,8 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
>  	/* Setup initial capable state. Will be updated later */
>  	link->aspm_capable = link->aspm_support;
>  
> +	link->aspm_disable = link->aspm_capable & ~link->aspm_default;
> +

This makes sense only in combination with patch 2. However I think patch 1
should be independent of patch 2. Especially if we consider patch 1 a fix
that is applied to stable whilst patch 2 is an improvement for next.

>  	/* Get and check endpoint acceptable latencies */
>  	list_for_each_entry(child, &linkbus->devices, bus_list) {
>  		u32 reg32, encoding;
> @@ -1226,11 +1228,15 @@ static ssize_t aspm_attr_store_common(struct device *dev,
>  	mutex_lock(&aspm_lock);
>  
>  	if (state_enable) {
> -		link->aspm_disable &= ~state;
>  		/* need to enable L1 for substates */
>  		if (state & ASPM_STATE_L1SS)
> -			link->aspm_disable &= ~ASPM_STATE_L1;
> +			state |= ASPM_STATE_L1;
> +
> +		link->aspm_disable &= ~state;

I don't see what this part of the patch changes. Can you elaborate on why
this is needed?

>  	} else {
> +		if (state == ASPM_STATE_L1)
> +			state |= ASPM_STATE_L1SS;
> +

I think this part should be sufficient to fix the behavior. because what
I think currently happens:

1. original status: policy powersupersave, nothing disabled -> L1 + L1SS active
2. disable L1: L1 disabled, pcie_config_aspm_link() disabled L1 and L1SS
   w/o adding L1SS to link-> aspm_disabled
3. enable one L1SS state: aspm_attr_store_common() removes L1 from
   link->aspm_disabled -> link->aspm_disabled is empty, resulting in
   L1 + L1SS being active

>  		link->aspm_disable |= state;
>  	}
>  
>