[PATCH v7 9/9] PCI: tegra194: Add ASPM L1 entrance latency config

From: Manikanta Maddireddy

Date: Tue Mar 03 2026 - 02:02:36 EST


For Tegra234, the HW PHY team conducted experiments and determined the
optimal ASPM L1 entrance latency values: 8 us for Root Port mode and
16 us for Endpoint mode. Update the default ASPM L1 entrance latency
configuration accordingly.

Reviewed-by: Jon Hunter <jonathanh@xxxxxxxxxx>
Tested-by: Jon Hunter <jonathanh@xxxxxxxxxx>
Reviewed-by: Vidya Sagar <vidyas@xxxxxxxxxx>
Signed-off-by: Manikanta Maddireddy <mmaddireddy@xxxxxxxxxx>
---
Changes V1 -> V7: None

drivers/pci/controller/dwc/pcie-tegra194.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
index e0455d322166..accb2f8d3de8 100644
--- a/drivers/pci/controller/dwc/pcie-tegra194.c
+++ b/drivers/pci/controller/dwc/pcie-tegra194.c
@@ -240,6 +240,8 @@ struct tegra_pcie_dw_of_data {
u32 cdm_chk_int_en_bit;
u32 gen4_preset_vec;
u8 n_fts[2];
+ /* L1 Latency entrance values(Rest/Prod) */
+ u32 aspm_l1_enter_lat;
};

struct tegra_pcie_dw {
@@ -710,6 +712,8 @@ static void init_host_aspm(struct tegra_pcie_dw *pcie)
val = dw_pcie_readl_dbi(pci, PCIE_PORT_AFR);
val &= ~PORT_AFR_L0S_ENTRANCE_LAT_MASK;
val |= (pcie->aspm_l0s_enter_lat << PORT_AFR_L0S_ENTRANCE_LAT_SHIFT);
+ val &= ~PORT_AFR_L1_ENTRANCE_LAT_MASK;
+ val |= (pcie->of_data->aspm_l1_enter_lat << PORT_AFR_L1_ENTRANCE_LAT_SHIFT);
val |= PORT_AFR_ENTER_ASPM;
dw_pcie_writel_dbi(pci, PCIE_PORT_AFR, val);
}
@@ -2472,6 +2476,7 @@ static const struct tegra_pcie_dw_of_data tegra194_pcie_dw_rc_of_data = {
/* Gen4 - 5, 6, 8 and 9 presets enabled */
.gen4_preset_vec = 0x360,
.n_fts = { 52, 52 },
+ .aspm_l1_enter_lat = 3,
};

static const struct tegra_pcie_dw_of_data tegra194_pcie_dw_ep_of_data = {
@@ -2481,6 +2486,7 @@ static const struct tegra_pcie_dw_of_data tegra194_pcie_dw_ep_of_data = {
/* Gen4 - 5, 6, 8 and 9 presets enabled */
.gen4_preset_vec = 0x360,
.n_fts = { 52, 52 },
+ .aspm_l1_enter_lat = 3,
};

static const struct tegra_pcie_dw_of_data tegra234_pcie_dw_rc_of_data = {
@@ -2493,6 +2499,7 @@ static const struct tegra_pcie_dw_of_data tegra234_pcie_dw_rc_of_data = {
/* Gen4 - 6, 8 and 9 presets enabled */
.gen4_preset_vec = 0x340,
.n_fts = { 52, 80 },
+ .aspm_l1_enter_lat = 4,
};

static const struct tegra_pcie_dw_of_data tegra234_pcie_dw_ep_of_data = {
@@ -2505,6 +2512,7 @@ static const struct tegra_pcie_dw_of_data tegra234_pcie_dw_ep_of_data = {
/* Gen4 - 6, 8 and 9 presets enabled */
.gen4_preset_vec = 0x340,
.n_fts = { 52, 80 },
+ .aspm_l1_enter_lat = 5,
};

static const struct of_device_id tegra_pcie_dw_of_match[] = {
--
2.34.1