@@ -42,6 +42,18 @@
#define ASPM_STATE_ALL (ASPM_STATE_L0S | ASPM_STATE_L1 | \
ASPM_STATE_L1SS)
+/*
+ * When L1 substates are enabled, the LTR L1.2 threshold is a timing parameter
+ * that decides whether L1.1 or L1.2 is entered (Refer PCIe spec for details).
+ * Not sure is there is a way to "calculate" this on the fly, but may be we
+ * could turn it into a parameter in future. This value has been taken from
+ * the following files from Intel's coreboot (which is the only code I found
+ * to have used this):
+ * https://www.coreboot.org/pipermail/coreboot-gerrit/2015-March/021134.html
+ * https://review.coreboot.org/#/c/8832/
+ */
+#define LTR_L1_2_THRESHOLD_BITS ((1 << 21) | (1 << 23) | (1 << 30))
+
struct aspm_latency {
u32 l0s; /* L0s latency (nsec) */
u32 l1; /* L1 latency (nsec) */
@@ -76,6 +88,14 @@ struct pcie_link_state {
* has one slot under it, so at most there are 8 functions.
*/
struct aspm_latency acceptable[8];
+
+ /* L1 PM Substate info */
+ struct {
+ u32 up_cap_ptr; /* L1SS cap ptr in upstream dev */
+ u32 dw_cap_ptr; /* L1SS cap ptr in downstream dev */
+ u32 ctl1; /* value to be programmed in ctl1 */
+ u32 ctl2; /* value to be programmed in ctl2 */
+ } l1ss;
};
static int aspm_disabled, aspm_force;
@@ -296,6 +316,22 @@ static u32 calc_l1_acceptable(u32 encoding)
return (1000 << encoding);
}
+/* Convert L1SS T_pwr encoding to usec */
+static u32 calc_l1ss_pwron(struct pci_dev *pdev, u32 scale, u32 val)
+{
+ switch (scale) {
+ case 0:
+ return val * 2;
+ case 1:
+ return val * 10;
+ case 2:
+ return val * 100;
+ }
+ dev_err(&pdev->dev, "%s: Invalid T_PwrOn scale: %u\n",
+ __func__, scale);
+ return 0;
+}
+
struct aspm_register_info {
u32 support:2;
u32 enabled:2;
@@ -392,6 +428,46 @@ static inline struct pci_dev *pci_function_0(struct pci_bus *linkbus)
return NULL;
}
+/* Calculate L1.2 PM substate timing parameters */
+static void aspm_calc_l1ss_info(struct pcie_link_state *link,
+ struct aspm_register_info *upreg,
+ struct aspm_register_info *dwreg)
+{
+ u32 val1, val2, scale1, scale2;
+
+ link->l1ss.up_cap_ptr = upreg->l1ss_cap_ptr;
+ link->l1ss.dw_cap_ptr = dwreg->l1ss_cap_ptr;
+ link->l1ss.ctl1 = link->l1ss.ctl2 = 0;
+
+ if (!(link->aspm_support & ASPM_STATE_L1_2_MASK))
+ return;
+
+ /* Choose the greater of the two T_cmn_mode_rstr_time */
+ val1 = (upreg->l1ss_cap >> 8) & 0xFF;
+ val2 = (upreg->l1ss_cap >> 8) & 0xFF;
+ if (val1 > val2)
+ link->l1ss.ctl1 |= val1 << 8;
+ else
+ link->l1ss.ctl1 |= val2 << 8;
+ /*
+ * We currently use LTR L1.2 threshold to be fixed constant picked from
+ * Intel's coreboot.
+ */
+ link->l1ss.ctl1 |= LTR_L1_2_THRESHOLD_BITS;
+
+ /* Choose the greater of the two T_pwr_on */
+ val1 = (upreg->l1ss_cap >> 19) & 0x1F;
+ scale1 = (upreg->l1ss_cap >> 16) & 0x03;
+ val2 = (dwreg->l1ss_cap >> 19) & 0x1F;
+ scale2 = (dwreg->l1ss_cap >> 16) & 0x03;
+
+ if (calc_l1ss_pwron(link->pdev, scale1, val1) >
+ calc_l1ss_pwron(link->downstream, scale2, val2))
+ link->l1ss.ctl2 |= scale1 | (val1 << 3);
+ else
+ link->l1ss.ctl2 |= scale2 | (val2 << 3);
+}
+
static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
{
struct pci_dev *child, *parent = link->pdev;
@@ -471,6 +547,9 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
if (upreg.l1ss_ctl1 & dwreg.l1ss_ctl1 & PCI_L1SS_CTL1_PCIPM_L1_2)
link->aspm_enabled |= ASPM_STATE_L1_2_PCIPM;
+ if (link->aspm_support & ASPM_STATE_L1SS)
+ aspm_calc_l1ss_info(link, &upreg, &dwreg);
+
/* Save default state */
link->aspm_default = link->aspm_enabled;
Calculate and save the timing parameters that need to be programmed if we need to enable L1.2 substates later. We use the same logic (and a constant value for 1 of the parameters) as used by Intel's coreboot: https://www.coreboot.org/pipermail/coreboot-gerrit/2015-March/021134.html https://review.coreboot.org/#/c/8832/ Signed-off-by: Rajat Jain <rajatja@google.com> --- drivers/pci/pcie/aspm.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 79 insertions(+)