diff options
Diffstat (limited to 'drivers/pci/pcie/aspm.c')
| -rw-r--r-- | drivers/pci/pcie/aspm.c | 71 |
1 files changed, 47 insertions, 24 deletions
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c index 9783e10da3a9..3b9b4d50cd98 100644 --- a/drivers/pci/pcie/aspm.c +++ b/drivers/pci/pcie/aspm.c @@ -43,18 +43,6 @@ #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 maybe 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) */ @@ -333,6 +321,32 @@ static u32 calc_l1ss_pwron(struct pci_dev *pdev, u32 scale, u32 val) return 0; } +static void encode_l12_threshold(u32 threshold_us, u32 *scale, u32 *value) +{ + u64 threshold_ns = threshold_us * 1000; + + /* See PCIe r3.1, sec 7.33.3 and sec 6.18 */ + if (threshold_ns < 32) { + *scale = 0; + *value = threshold_ns; + } else if (threshold_ns < 1024) { + *scale = 1; + *value = threshold_ns >> 5; + } else if (threshold_ns < 32768) { + *scale = 2; + *value = threshold_ns >> 10; + } else if (threshold_ns < 1048576) { + *scale = 3; + *value = threshold_ns >> 15; + } else if (threshold_ns < 33554432) { + *scale = 4; + *value = threshold_ns >> 20; + } else { + *scale = 5; + *value = threshold_ns >> 25; + } +} + struct aspm_register_info { u32 support:2; u32 enabled:2; @@ -443,6 +457,7 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link, struct aspm_register_info *dwreg) { u32 val1, val2, scale1, scale2; + u32 t_common_mode, t_power_on, l1_2_threshold, scale, value; link->l1ss.up_cap_ptr = upreg->l1ss_cap_ptr; link->l1ss.dw_cap_ptr = dwreg->l1ss_cap_ptr; @@ -454,16 +469,7 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link, /* Choose the greater of the two Port Common_Mode_Restore_Times */ val1 = (upreg->l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8; val2 = (dwreg->l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8; - 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; + t_common_mode = max(val1, val2); /* Choose the greater of the two Port T_POWER_ON times */ val1 = (upreg->l1ss_cap & PCI_L1SS_CAP_P_PWR_ON_VALUE) >> 19; @@ -472,10 +478,27 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link, scale2 = (dwreg->l1ss_cap & PCI_L1SS_CAP_P_PWR_ON_SCALE) >> 16; if (calc_l1ss_pwron(link->pdev, scale1, val1) > - calc_l1ss_pwron(link->downstream, scale2, val2)) + calc_l1ss_pwron(link->downstream, scale2, val2)) { link->l1ss.ctl2 |= scale1 | (val1 << 3); - else + t_power_on = calc_l1ss_pwron(link->pdev, scale1, val1); + } else { link->l1ss.ctl2 |= scale2 | (val2 << 3); + t_power_on = calc_l1ss_pwron(link->downstream, scale2, val2); + } + + /* + * Set LTR_L1.2_THRESHOLD to the time required to transition the + * Link from L0 to L1.2 and back to L0 so we enter L1.2 only if + * downstream devices report (via LTR) that they can tolerate at + * least that much latency. + * + * Based on PCIe r3.1, sec 5.5.3.3.1, Figures 5-16 and 5-17, and + * Table 5-11. T(POWER_OFF) is at most 2us and T(L1.2) is at + * least 4us. + */ + l1_2_threshold = 2 + 4 + t_common_mode + t_power_on; + encode_l12_threshold(l1_2_threshold, &scale, &value); + link->l1ss.ctl1 |= t_common_mode << 8 | scale << 29 | value << 16; } static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist) |
