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PCI/ASPM: Stop caching link L0s, L1 exit latencies 

Previously we calculated the upstream and downstream L0s and L1 exit
latencies of the link in pcie_aspm_cap_init() and cached them in struct
pcie_link_state.latency_*.

These values are only used in pcie_aspm_check_latency() where they are
compared with the acceptable latencies on 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 latency_*
entries from struct pcie_link_state and calculate the latencies directly
where they are needed.

Link: https://lore.kernel.org/r/20211119193732.12343-3-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 20:37:30 +01:00 committed by Bjorn Helgaas
parent 43262f001b
commit 222578dad4
1 changed files with 17 additions and 11 deletions
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28
drivers/pci/pcie/aspm.c
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@ -66,9 +66,6 @@ struct pcie_link_state {
u32 clkpm_default:1; /* Default Clock PM state by BIOS */
u32 clkpm_disable:1; /* Clock PM disabled */
/* Exit latencies */
struct aspm_latency latency_up; /* Upstream direction exit latency */
struct aspm_latency latency_dw; /* Downstream direction exit latency */
/*
* Endpoint acceptable latencies. A pcie downstream port only
* has one slot under it, so at most there are 8 functions.
@ -392,7 +389,8 @@ static void encode_l12_threshold(u32 threshold_us, u32 *scale, u32 *value)
static void pcie_aspm_check_latency(struct pci_dev *endpoint)
{
u32 latency, l1_switch_latency = 0;
u32 latency, lnkcap_up, lnkcap_dw, l1_switch_latency = 0;
struct aspm_latency latency_up, latency_dw;
struct aspm_latency *acceptable;
struct pcie_link_state *link;
@ -405,14 +403,26 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
acceptable = &link->acceptable[PCI_FUNC(endpoint->devfn)];
while (link) {
struct pci_dev *dev = pci_function_0(link->pdev->subordinate);
/* Read direction exit latencies */
pcie_capability_read_dword(link->pdev, PCI_EXP_LNKCAP,
&lnkcap_up);
pcie_capability_read_dword(dev, PCI_EXP_LNKCAP,
&lnkcap_dw);
latency_up.l0s = calc_l0s_latency(lnkcap_up);
latency_up.l1 = calc_l1_latency(lnkcap_up);
latency_dw.l0s = calc_l0s_latency(lnkcap_dw);
latency_dw.l1 = calc_l1_latency(lnkcap_dw);
/* Check upstream direction L0s latency */
if ((link->aspm_capable & ASPM_STATE_L0S_UP) &&
(link->latency_up.l0s > acceptable->l0s))
(latency_up.l0s > acceptable->l0s))
link->aspm_capable &= ~ASPM_STATE_L0S_UP;
/* Check downstream direction L0s latency */
if ((link->aspm_capable & ASPM_STATE_L0S_DW) &&
(link->latency_dw.l0s > acceptable->l0s))
(latency_dw.l0s > acceptable->l0s))
link->aspm_capable &= ~ASPM_STATE_L0S_DW;
/*
* Check L1 latency.
@ -427,7 +437,7 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
* L1 exit latencies advertised by a device include L1
* substate latencies (and hence do not do any check).
*/
latency = max_t(u32, link->latency_up.l1, link->latency_dw.l1);
latency = max_t(u32, latency_up.l1, latency_dw.l1);
if ((link->aspm_capable & ASPM_STATE_L1) &&
(latency + l1_switch_latency > acceptable->l1))
link->aspm_capable &= ~ASPM_STATE_L1;
@ -593,8 +603,6 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
link->aspm_enabled |= ASPM_STATE_L0S_UP;
if (parent_lnkctl & PCI_EXP_LNKCTL_ASPM_L0S)
link->aspm_enabled |= ASPM_STATE_L0S_DW;
link->latency_up.l0s = calc_l0s_latency(parent_lnkcap);
link->latency_dw.l0s = calc_l0s_latency(child_lnkcap);
/* Setup L1 state */
if (parent_lnkcap & child_lnkcap & PCI_EXP_LNKCAP_ASPM_L1)
@ -602,8 +610,6 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
if (parent_lnkctl & child_lnkctl & PCI_EXP_LNKCTL_ASPM_L1)
link->aspm_enabled |= ASPM_STATE_L1;
link->latency_up.l1 = calc_l1_latency(parent_lnkcap);
link->latency_dw.l1 = calc_l1_latency(child_lnkcap);
/* Setup L1 substate */
pci_read_config_dword(parent, parent->l1ss + PCI_L1SS_CAP,