[RFC PATCH v5 3/4] PCI/ASPM: Remove struct pcie_link_state.acceptable

Saheed O. Bolarinwa
2021-11-19T19:39:36Z

The acceptable latencies for each device on the bus are calculated within
pcie_aspm_cap_init() and cached in struct pcie_link_state.acceptable.
They are only used within pcie_aspm_check_latency() to validate actual
latencies. Thus, it is possible to avoid caching these values.

- remove `acceptable` from struct pcie_link_state
- calculate the acceptable latency for individual device directly
- remove the calculations done within pcie_aspm_cap_init()

Signed-off-by: Saheed O. Bolarinwa <refactormyself@gmail.com>
---
drivers/pci/pcie/aspm.c | 28 +++++++++-------------------
1 file changed, 9 insertions(+), 19 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 1b8933e0afb2..a8821fe1ffe7 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -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 reg32, 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 +395,13 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
return;

link = endpoint->bus->self->link_state;
- acceptable = &link->acceptable[PCI_FUNC(endpoint->devfn)];
+ pcie_capability_read_dword(endpoint, 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);

while (link) {
struct pci_dev *dev = pci_function_0(
@@ -669,22 +670,11 @@ 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);
}
}
--
2.20.1