[RFC PATCH 1/3] PCI/ASPM: Remove struct pcie_link_state.latency_*

["Saheed O. Bolarinwa" <refactormyself@gmail.com>]

Inside pcie_aspm_cap_init() the exit latencies on both upstream and
downstream are calculated 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.

Computing these latencies right inside pcie_aspm_check_latency() where
they are only needed will remove the need for caching them. This will
not make any functional change.

 - Calculate the exit latencies inside pcie_aspm_check_latency()
 - Remove struct pcie_link_state.latency_{up,dw}
 - Replace references with local variables of struct aspm_latency

Signed-off-by: Saheed O. Bolarinwa <refactormyself@gmail.com>
---
 drivers/pci/pcie/aspm.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 013a47f587ce..4c437b1345b2 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.
@@ -378,7 +375,8 @@ 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;
 
@@ -391,14 +389,22 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
 	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(link->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 +419,7 @@ 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 +599,6 @@ 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 +606,6 @@ 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