PCI: tegra194: Set LTR message request before PCIe link up in Endpoint mode

[ Upstream commit b256493 ]

LTR message should be sent as soon as the Root Port enables LTR in the
Endpoint mode. So set snoop and no-snoop LTR timing and LTR message request
before the PCIe link comes up, so that the LTR message is sent upstream as
soon as LTR is enabled.

Without programming these values, the Endpoint would send latencies of 0 to
the host, which will be inaccurate.

Fixes: c57247f ("PCI: tegra: Add support for PCIe endpoint mode in Tegra194")
Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
[mani: commit log]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Link: https://patch.msgid.link/20260324190755.1094879-9-mmaddireddy@nvidia.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: Vidya Sagar

drivers/pci/controller/dwc/pcie-tegra194.c

@@ -487,15 +487,6 @@ static irqreturn_t tegra_pcie_ep_irq_thread(int irq, void *arg)
 	if (val & PCI_COMMAND_MASTER) {
 		ktime_t timeout;
 
-		/* 110us for both snoop and no-snoop */
-		val = FIELD_PREP(PCI_LTR_VALUE_MASK, 110) |
-		      FIELD_PREP(PCI_LTR_SCALE_MASK, 2) |
-		      LTR_MSG_REQ |
-		      FIELD_PREP(PCI_LTR_NOSNOOP_VALUE, 110) |
-		      FIELD_PREP(PCI_LTR_NOSNOOP_SCALE, 2) |
-		      LTR_NOSNOOP_MSG_REQ;
-		appl_writel(pcie, val, APPL_LTR_MSG_1);
-
 		/* Send LTR upstream */
 		val = appl_readl(pcie, APPL_LTR_MSG_2);
 		val |= APPL_LTR_MSG_2_LTR_MSG_REQ_STATE;
@@ -1832,6 +1823,15 @@ static void pex_ep_event_pex_rst_deassert(struct tegra_pcie_dw *pcie)
 	val |= APPL_INTR_EN_L1_0_0_RDLH_LINK_UP_INT_EN;
 	appl_writel(pcie, val, APPL_INTR_EN_L1_0_0);
 
+	/* 110us for both snoop and no-snoop */
+	val = FIELD_PREP(PCI_LTR_VALUE_MASK, 110) |
+	      FIELD_PREP(PCI_LTR_SCALE_MASK, 2) |
+	      LTR_MSG_REQ |
+	      FIELD_PREP(PCI_LTR_NOSNOOP_VALUE, 110) |
+	      FIELD_PREP(PCI_LTR_NOSNOOP_SCALE, 2) |
+	      LTR_NOSNOOP_MSG_REQ;
+	appl_writel(pcie, val, APPL_LTR_MSG_1);
+
 	reset_control_deassert(pcie->core_rst);
 
 	val = dw_pcie_readl_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL);