linux-kernel - [PATCH V4 14/22] PCI: tegra194: Set LTR message request before PCIe link up

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Message-ID: <20260126074519.3426742-15-mmaddireddy@nvidia.com>
Date: Mon, 26 Jan 2026 13:15:11 +0530
From: Manikanta Maddireddy <mmaddireddy@...dia.com>
To: <bhelgaas@...gle.com>, <lpieralisi@...nel.org>, <kwilczynski@...nel.org>,
	<mani@...nel.org>, <robh@...nel.org>, <krzk+dt@...nel.org>,
	<conor+dt@...nel.org>, <thierry.reding@...il.com>, <jonathanh@...dia.com>,
	<jingoohan1@...il.com>, <vidyas@...dia.com>, <cassel@...nel.org>,
	<18255117159@....com>
CC: <linux-pci@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>, "Manikanta
 Maddireddy" <mmaddireddy@...dia.com>
Subject: [PATCH V4 14/22] PCI: tegra194: Set LTR message request before PCIe link up

From: Vidya Sagar <vidyas@...dia.com>

LTR message should be sent as soon as the root port enables LTR in the
endpoint. Set snoop & no snoop LTR timing and LTR message request before
PCIe links up. This ensures that LTR message is sent upstream as soon as
LTR is enabled.

Signed-off-by: Vidya Sagar <vidyas@...dia.com>
Signed-off-by: Manikanta Maddireddy <mmaddireddy@...dia.com>
---
V4:
* None

V3:
* This is a new patch in this series

 drivers/pci/controller/dwc/pcie-tegra194.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
index 5a3e85c53dd7..6fcfff93d4bc 100644
--- a/drivers/pci/controller/dwc/pcie-tegra194.c
+++ b/drivers/pci/controller/dwc/pcie-tegra194.c
@@ -126,6 +126,7 @@
 
 #define APPL_LTR_MSG_1				0xC4
 #define LTR_MSG_REQ				BIT(15)
+#define LTR_MST_NO_SNOOP_SHIFT			16
 #define LTR_NOSNOOP_MSG_REQ			BIT(31)
 
 #define APPL_LTR_MSG_2				0xC8
@@ -491,15 +492,6 @@ 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;
@@ -1879,6 +1871,11 @@ static void pex_ep_event_pex_rst_deassert(struct tegra_pcie_dw *pcie)
 	val |= APPL_INTR_EN_L1_8_EDMA_INT_EN;
 	appl_writel(pcie, val, APPL_INTR_EN_L1_8_0);
 
+	/* 110us for both snoop and no-snoop */
+	val = 110 | (2 << PCI_LTR_SCALE_SHIFT) | LTR_MSG_REQ;
+	val |= (val << LTR_MST_NO_SNOOP_SHIFT);
+	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);
-- 
2.34.1