PCI: rockchip: Increase the Max Credit update interval
Increase the likelihood of link state to automatically go to L1 and save
some power.
The default credit update interval of 7.5 us results in the rootport
sending UpdateFC-P and UpdateFC-NP packets too often, thus resulting in the
link never going to L1, and always staying in L0/L0s. The value 24 us was
chosen after some experiments and peeking over the PCIe bus to see that we
do enter L1 substate when there is not enough traffic on the PCIe bus.
Signed-off-by: Rajat Jain <rajatja@google.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Shawn Lin <shawn.lin@rock-chips.com>
diff --git a/drivers/pci/host/pcie-rockchip.c b/drivers/pci/host/pcie-rockchip.c
index 8bedc1e..91f6fa2 100644
--- a/drivers/pci/host/pcie-rockchip.c
+++ b/drivers/pci/host/pcie-rockchip.c
@@ -95,6 +95,11 @@
#define PCIE_CORE_PL_CONF_SPEED_MASK 0x00000018
#define PCIE_CORE_PL_CONF_LANE_MASK 0x00000006
#define PCIE_CORE_PL_CONF_LANE_SHIFT 1
+#define PCIE_CORE_TXCREDIT_CFG1 (PCIE_CORE_CTRL_MGMT_BASE + 0x020)
+#define PCIE_CORE_TXCREDIT_CFG1_MUI_MASK 0xFFFF0000
+#define PCIE_CORE_TXCREDIT_CFG1_MUI_SHIFT 16
+#define PCIE_CORE_TXCREDIT_CFG1_MUI_ENCODE(x) \
+ (((x) >> 3) << PCIE_CORE_TXCREDIT_CFG1_MUI_SHIFT)
#define PCIE_CORE_INT_STATUS (PCIE_CORE_CTRL_MGMT_BASE + 0x20c)
#define PCIE_CORE_INT_PRFPE BIT(0)
#define PCIE_CORE_INT_CRFPE BIT(1)
@@ -224,6 +229,17 @@
rockchip_pcie_write(rockchip, status, PCIE_RC_CONFIG_LCS);
}
+static void rockchip_pcie_update_txcredit_mui(struct rockchip_pcie *rockchip)
+{
+ u32 val;
+
+ /* Update Tx credit maximum update interval */
+ val = rockchip_pcie_read(rockchip, PCIE_CORE_TXCREDIT_CFG1);
+ val &= ~PCIE_CORE_TXCREDIT_CFG1_MUI_MASK;
+ val |= PCIE_CORE_TXCREDIT_CFG1_MUI_ENCODE(24000); /* ns */
+ rockchip_pcie_write(rockchip, val, PCIE_CORE_TXCREDIT_CFG1);
+}
+
static int rockchip_pcie_valid_device(struct rockchip_pcie *rockchip,
struct pci_bus *bus, int dev)
{
@@ -597,6 +613,7 @@
rockchip_pcie_write(rockchip, sub_reg, PCIE_CORE_INT_STATUS);
} else if (reg & PCIE_CLIENT_INT_PHY) {
dev_dbg(dev, "phy link changes\n");
+ rockchip_pcie_update_txcredit_mui(rockchip);
rockchip_pcie_clr_bw_int(rockchip);
}