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PCI/ASPM: Stop caching device L0s, L1 acceptable exit latencies

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Previously we calculated the device's acceptable L0s and L1 exit latencies
in pcie_aspm_cap_init() and cached them in struct pcie_link_state.

These values are only used in pcie_aspm_check_latency() where they are
compared with the actual exit latencies of the link.  This path is used
when removing or changing the D state of the device, so it's relatively low
frequency.

To reduce the amount of per-link data we store, remove the acceptable[]
arrays from struct pcie_link_state and calculate them directly from the
already-cached Device Capabilities register when needed.

[bhelgaas: use endpoint->devcap instead of reading it again]
Link: https://lore.kernel.org/r/20211119193732.12343-4-refactormyself@gmail.com
Signed-off-by: Saheed O. Bolarinwa <refactormyself@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
Saheed O. Bolarinwa 2021-11-19 20:37:31 +01:00 committed by Bjorn Helgaas
parent 222578dad4
commit 6e332df7c3
1 changed files with 10 additions and 19 deletions
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29
drivers/pci/pcie/aspm.c
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@ -65,12 +65,6 @@ struct pcie_link_state {
u32 clkpm_enabled:1; /* Current Clock PM state */
u32 clkpm_default:1; /* Default Clock PM state by BIOS */
u32 clkpm_disable:1; /* Clock PM disabled */
/*
* Endpoint acceptable latencies. A pcie downstream port only
* has one slot under it, so at most there are 8 functions.
*/
struct aspm_latency acceptable[8];
};
static int aspm_disabled, aspm_force;
@ -389,7 +383,8 @@ static void encode_l12_threshold(u32 threshold_us, u32 *scale, u32 *value)
static void pcie_aspm_check_latency(struct pci_dev *endpoint)
{
u32 latency, lnkcap_up, lnkcap_dw, l1_switch_latency = 0;
u32 latency, encoding, lnkcap_up, lnkcap_dw;
u32 l1_switch_latency = 0;
struct aspm_latency latency_up, latency_dw;
struct aspm_latency *acceptable;
struct pcie_link_state *link;
@ -400,7 +395,14 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
return;
link = endpoint->bus->self->link_state;
acceptable = &link->acceptable[PCI_FUNC(endpoint->devfn)];
/* Calculate endpoint L0s acceptable latency */
encoding = (endpoint->devcap & PCI_EXP_DEVCAP_L0S) >> 6;
acceptable->l0s = calc_l0s_acceptable(encoding);
/* Calculate endpoint L1 acceptable latency */
encoding = (endpoint->devcap & PCI_EXP_DEVCAP_L1) >> 9;
acceptable->l1 = calc_l1_acceptable(encoding);
while (link) {
struct pci_dev *dev = pci_function_0(link->pdev->subordinate);
@ -666,22 +668,11 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
/* Get and check endpoint acceptable latencies */
list_for_each_entry(child, &linkbus->devices, bus_list) {
u32 reg32, encoding;
struct aspm_latency *acceptable =
&link->acceptable[PCI_FUNC(child->devfn)];
if (pci_pcie_type(child) != PCI_EXP_TYPE_ENDPOINT &&
pci_pcie_type(child) != PCI_EXP_TYPE_LEG_END)
continue;
pcie_capability_read_dword(child, PCI_EXP_DEVCAP, &reg32);
/* Calculate endpoint L0s acceptable latency */
encoding = (reg32 & PCI_EXP_DEVCAP_L0S) >> 6;
acceptable->l0s = calc_l0s_acceptable(encoding);
/* Calculate endpoint L1 acceptable latency */
encoding = (reg32 & PCI_EXP_DEVCAP_L1) >> 9;
acceptable->l1 = calc_l1_acceptable(encoding);
pcie_aspm_check_latency(child);
}
}