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Date: Wed, 25 Jan 2023 22:52:03 +0530
From: Vidya Sagar <vidyas@...dia.com>
To: "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
bhelgaas@...gle.com, sathyanarayanan.kuppuswamy@...ux.intel.com,
kai.heng.feng@...onical.com
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
treding@...dia.com, jonathanh@...dia.com, kthota@...dia.com,
mmaddireddy@...dia.com, sagar.tv@...il.com
Subject: Re: [PATCH V1] PCI/ASPM: Update saved buffers with latest ASPM
configuration
On 1/25/2023 8:31 PM, Wysocki, Rafael J wrote:
> External email: Use caution opening links or attachments
>
>
> On 1/25/2023 2:38 PM, Vidya Sagar wrote:
>> Many PCIe device drivers save the configuration state of their respective
>> devices during probe and restore the same when their 'slot_reset' hook
>> is called through PCIe Error Recovery System.
>> If the system has a change in ASPM policy after the driver's probe is
>> called and before error event occurred, 'slot_reset' hook restores the
>> PCIe configuration state to what it was at the time of probe but not with
>> what it was just before the occurrence of the error event.
>> This effectively leads to a mismatch in the ASPM configuration between
>> the device and its upstream parent device.
>> This patch addresses that issue by updating the saved configuration state
>> of the device with the latest info whenever there is a change w.r.t ASPM
>> policy.
>>
>> Signed-off-by: Vidya Sagar <vidyas@...dia.com>
>
> If it is a bug fix (which I think it is), a Fixes tag should be present
> here.
It is kind of a bug fix but I couldn't pin point to any particular
commit that would have introduced it.
>
> If the reporter's names are known, Reported-by tags should be present
> here too.
I was experimenting with the error handling code and happen to find this.
>
> If anyone except for you has tested this patch, a Tested-by tag should
> be present here.
Only I tested this patch for now. It would be great if more verification
is done on this patch.
Thanks,
Vidya Sagar
>
>> ---
>> drivers/pci/pci.h | 4 ++++
>> drivers/pci/pcie/aspm.c | 40 ++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 44 insertions(+)
>>
>> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
>> index 9ed3b5550043..f4a91d4fe96d 100644
>> --- a/drivers/pci/pci.h
>> +++ b/drivers/pci/pci.h
>> @@ -566,12 +566,16 @@ bool pcie_wait_for_link(struct pci_dev *pdev,
>> bool active);
>> void pcie_aspm_init_link_state(struct pci_dev *pdev);
>> void pcie_aspm_exit_link_state(struct pci_dev *pdev);
>> void pcie_aspm_powersave_config_link(struct pci_dev *pdev);
>> +void pci_save_aspm_state(struct pci_dev *dev);
>> +void pci_restore_aspm_state(struct pci_dev *dev);
>> void pci_save_aspm_l1ss_state(struct pci_dev *dev);
>> void pci_restore_aspm_l1ss_state(struct pci_dev *dev);
>> #else
>> static inline void pcie_aspm_init_link_state(struct pci_dev *pdev) { }
>> static inline void pcie_aspm_exit_link_state(struct pci_dev *pdev) { }
>> static inline void pcie_aspm_powersave_config_link(struct pci_dev
>> *pdev) { }
>> +static inline void pci_save_aspm_state(struct pci_dev *dev) { }
>> +static inline void pci_restore_aspm_state(struct pci_dev *dev) { }
>> static inline void pci_save_aspm_l1ss_state(struct pci_dev *dev) { }
>> static inline void pci_restore_aspm_l1ss_state(struct pci_dev *dev) { }
>> #endif
>> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
>> index 53a1fa306e1e..f25e0440d36b 100644
>> --- a/drivers/pci/pcie/aspm.c
>> +++ b/drivers/pci/pcie/aspm.c
>> @@ -151,6 +151,7 @@ static void pcie_set_clkpm_nocheck(struct
>> pcie_link_state *link, int enable)
>>
>> PCI_EXP_LNKCTL_CLKREQ_EN,
>> val);
>> link->clkpm_enabled = !!enable;
>> + pci_save_aspm_state(child);
>> }
>>
>> static void pcie_set_clkpm(struct pcie_link_state *link, int enable)
>> @@ -757,6 +758,39 @@ static void pcie_config_aspm_l1ss(struct
>> pcie_link_state *link, u32 state)
>> PCI_L1SS_CTL1_L1SS_MASK, val);
>> }
>>
>> +void pci_save_aspm_state(struct pci_dev *dev)
>> +{
>> + int i = 0;
>> + struct pci_cap_saved_state *save_state;
>> + u16 *cap;
>> +
>> + if (!pci_is_pcie(dev))
>> + return;
>> +
>> + save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
>> + if (!save_state)
>> + return;
>> +
>> + cap = (u16 *)&save_state->cap.data[0];
>> + i++;
>> + pcie_capability_read_word(dev, PCI_EXP_LNKCTL, &cap[i++]);
>> +}
>> +
>> +void pci_restore_aspm_state(struct pci_dev *dev)
>> +{
>> + int i = 0;
>> + struct pci_cap_saved_state *save_state;
>> + u16 *cap;
>> +
>> + save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
>> + if (!save_state)
>> + return;
>> +
>> + cap = (u16 *)&save_state->cap.data[0];
>> + i++;
>> + pcie_capability_write_word(dev, PCI_EXP_LNKCTL, cap[i++]);
>> +}
>> +
>> void pci_save_aspm_l1ss_state(struct pci_dev *dev)
>> {
>> struct pci_cap_saved_state *save_state;
>> @@ -849,6 +883,12 @@ static void pcie_config_aspm_link(struct
>> pcie_link_state *link, u32 state)
>> pcie_config_aspm_dev(parent, upstream);
>>
>> link->aspm_enabled = state;
>> +
>> + /* Update latest ASPM configuration in saved context */
>> + pci_save_aspm_state(link->downstream);
>> + pci_save_aspm_l1ss_state(link->downstream);
>> + pci_save_aspm_state(parent);
>> + pci_save_aspm_l1ss_state(parent);
>> }
>>
>> static void pcie_config_aspm_path(struct pcie_link_state *link)
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