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Date: Wed, 29 Sep 2021 02:41:14 +0200
From: "Saheed O. Bolarinwa" <refactormyself@...il.com>
To: helgaas@...nel.org
Cc: "Saheed O. Bolarinwa" <refactormyself@...il.com>,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v3 1/3] PCI/ASPM: Do not cache link latencies
The latencies of the upstream and downstream are calculated within
pcie_aspm_cap_init() and cached 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 patch:
- removes `latency_*` entries from struct pcie_link_state.
- calculates the latencies directly where they are needed.
- moves pci_function_0() upward, so that the downstream device can be
obtained by calling it directly.
- further removes dependencies on struct pcie_link_state.
Signed-off-by: Saheed O. Bolarinwa <refactormyself@...il.com>
---
drivers/pci/pcie/aspm.c | 54 ++++++++++++++++++++++-------------------
1 file changed, 29 insertions(+), 25 deletions(-)
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 013a47f587ce..9e85dfc56657 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -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.
@@ -376,9 +373,25 @@ static void encode_l12_threshold(u32 threshold_us, u32 *scale, u32 *value)
}
}
+/*
+ * The L1 PM substate capability is only implemented in function 0 in a
+ * multi function device.
+ */
+static struct pci_dev *pci_function_0(struct pci_bus *linkbus)
+{
+ struct pci_dev *child;
+
+ list_for_each_entry(child, &linkbus->devices, bus_list)
+ if (PCI_FUNC(child->devfn) == 0)
+ return child;
+ return NULL;
+}
+
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 pci_dev *downstream;
+ struct aspm_latency latency_up, latency_dw;
struct aspm_latency *acceptable;
struct pcie_link_state *link;
@@ -388,17 +401,26 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
return;
link = endpoint->bus->self->link_state;
+ downstream = pci_function_0(link->pdev->subordinate);
acceptable = &link->acceptable[PCI_FUNC(endpoint->devfn)];
while (link) {
+ /* Read direction exit latencies */
+ pcie_capability_read_dword(link->pdev, PCI_EXP_LNKCAP, &lnkcap_up);
+ pcie_capability_read_dword(downstream, 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.
@@ -413,7 +435,7 @@ 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;
@@ -423,20 +445,6 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
}
}
-/*
- * The L1 PM substate capability is only implemented in function 0 in a
- * multi function device.
- */
-static struct pci_dev *pci_function_0(struct pci_bus *linkbus)
-{
- struct pci_dev *child;
-
- list_for_each_entry(child, &linkbus->devices, bus_list)
- if (PCI_FUNC(child->devfn) == 0)
- return child;
- return NULL;
-}
-
static void pci_clear_and_set_dword(struct pci_dev *pdev, int pos,
u32 clear, u32 set)
{
@@ -593,8 +601,6 @@ 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 +608,6 @@ 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,
--
2.20.1
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