Most of our systems do not have FW or ACPI, so it is up to the RC driver to
set the maximum LTR {no-}snoop latency values of downstream devices. We
set them to a value that is slightly smaller than the value of our internal
bus timeout register.
Signed-off-by: Jim Quinlan <james.quinlan@xxxxxxxxxxxx>
---
drivers/pci/controller/pcie-brcmstb.c | 68 ++++++++++++++++++++++++++-
1 file changed, 66 insertions(+), 2 deletions(-)
diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
index e3480ca4cd57..3d08b92d5bb8 100644
--- a/drivers/pci/controller/pcie-brcmstb.c
+++ b/drivers/pci/controller/pcie-brcmstb.c
@@ -182,6 +182,20 @@
#define DATA_ADDR(pcie) (pcie->reg_offsets[EXT_CFG_DATA])
#define PCIE_RGR1_SW_INIT_1(pcie) (pcie->reg_offsets[RGR1_SW_INIT_1])
+/*
+ * What we call "LTR_FMT" is the 16 bit latency field format:
+ * [15:15] Requirement bit
+ * [12:10] Latency scale
+ * [09:00] Latency value
+ */
+#define LTR_FMT_TO_NS(p) (FIELD_GET(GENMASK(15, 15), (p)) \
+ * ((unsigned long long)FIELD_GET(GENMASK(9, 0), (p)) \
+ << (FIELD_GET(GENMASK(12, 10), (p)) * 5)))
+#define BRCM_LTR_MAX_SCALE 4 /* Scale==4 => Each unit is 1,048,576ns */
+#define BRCM_LTR_MAX_VALUE 9 /* Using the above scale, roughly 9.4 ms */
+#define BRCM_LTR_MAX_NS ((unsigned long long)(BRCM_LTR_MAX_VALUE \
+ << (5 * BRCM_LTR_MAX_SCALE)))
+
/* Rescal registers */
#define PCIE_DVT_PMU_PCIE_PHY_CTRL 0xc700
#define PCIE_DVT_PMU_PCIE_PHY_CTRL_DAST_NFLDS 0x3
@@ -679,6 +693,49 @@ static void brcm_extend_internal_bus_timeout(struct brcm_pcie *pcie, u32 nsec)
writel(216 * timeout_us, pcie->base + REG_OFFSET);
}
+/* Sets downstream device latency tolerance registers to max we can handle */
+static int brcm_set_dev_ltr_max(struct pci_dev *dev, void *data)
+{
+ u16 ltr_cap_offset = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_LTR);
+ u16 ltr_fmt_cur, ltr_fmt = *(u16 *)data;
+ unsigned long long cur_nsec;
+ static const u16 reg_offsets[2] = {
+ PCI_LTR_MAX_SNOOP_LAT,
+ PCI_LTR_MAX_NOSNOOP_LAT,
+ };
+ unsigned int i;
+
+ if (!ltr_cap_offset || !dev->ltr_path)
+ return 0;
+
+ /*
+ * FW may have already written a value so we want to respect that
+ * value if it is lower than ltr_fmt. Update the current value if
+ * it is 0 or if the new value is less than the current.
+ */
+ for (i = 0; i < ARRAY_SIZE(reg_offsets); i++) {
+ pci_read_config_word(dev, ltr_cap_offset + reg_offsets[i],
+ <r_fmt_cur);
+ cur_nsec = LTR_FMT_TO_NS(ltr_fmt_cur);
+ if (cur_nsec == 0 || cur_nsec > BRCM_LTR_MAX_NS)
+ pci_write_config_word(dev, ltr_cap_offset
+ + reg_offsets[i], ltr_fmt);
+ }
+
+ return 0;
+}
+
+void brcm_set_downstream_devs_ltr_max(struct brcm_pcie *pcie)
+{
+ struct pci_host_bridge *bridge = pci_host_bridge_from_priv(pcie);
+ u16 ltr_fmt = FIELD_PREP(GENMASK(9, 0), BRCM_LTR_MAX_VALUE)
+ | FIELD_PREP(GENMASK(12, 10), BRCM_LTR_MAX_SCALE)
+ | GENMASK(15, 15);
+
+ if (bridge->native_ltr)
+ pci_walk_bus(bridge->bus, brcm_set_dev_ltr_max, <r_fmt);
+}
+
/* The controller is capable of serving in both RC and EP roles */
static bool brcm_pcie_rc_mode(struct brcm_pcie *pcie)
{
@@ -1074,8 +1131,12 @@ static int brcm_pcie_start_link(struct brcm_pcie *pcie)
return -ENODEV;
}
- /* Extend internal bus timeout to 8ms or so */
- brcm_extend_internal_bus_timeout(pcie, SZ_8M);
+ /*
+ * Extend internal bus timeout to 8-10ms, specifically to a value
+ * that is slightly larger than what we are using for the max
+ * {no-}snoop latency we will set in downstream devices.
+ */
+ brcm_extend_internal_bus_timeout(pcie, BRCM_LTR_MAX_NS + 1000);
if (pcie->gen)
brcm_pcie_set_gen(pcie, pcie->gen);
@@ -1616,6 +1677,9 @@ static int brcm_pcie_probe(struct platform_device *pdev)
return ret;
}
+ if (IS_ENABLED(CONFIG_PCIEASPM))
+ brcm_set_downstream_devs_ltr_max(pcie);
+
return 0;
fail:
--
2.17.1
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