[PATCH v8 03/14] PCI: tegra194: Disable LTSSM after transition to detect on surprise down

[Manikanta Maddireddy]

After the link reaches a detect-related LTSSM state, disable LTSSM so it does
not keep toggling between polling and detect. Do this by polling for the
detect state first, then clearing APPL_CTRL_LTSSM_EN in both
tegra_pcie_dw_pme_turnoff() and pex_ep_event_pex_rst_assert().

Fixes: 56e15a238d92 ("PCI: tegra: Add Tegra194 PCIe support")
Reviewed-by: Jon Hunter <jonathanh@xxxxxxxxxx>
Tested-by: Jon Hunter <jonathanh@xxxxxxxxxx>
Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
Signed-off-by: Manikanta Maddireddy <mmaddireddy@xxxxxxxxxx>
---
Changes V8: Split into two patches

 drivers/pci/controller/dwc/pcie-tegra194.c | 29 ++++++++++++----------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
index 5b243c006562..baee73438638 100644
--- a/drivers/pci/controller/dwc/pcie-tegra194.c
+++ b/drivers/pci/controller/dwc/pcie-tegra194.c
@@ -1594,14 +1594,6 @@ static void tegra_pcie_dw_pme_turnoff(struct tegra_pcie_dw *pcie)
 		data &= ~APPL_PINMUX_PEX_RST;
 		appl_writel(pcie, data, APPL_PINMUX);
 
-		/*
-		 * Some cards do not go to detect state even after de-asserting
-		 * PERST#. So, de-assert LTSSM to bring link to detect state.
-		 */
-		data = readl(pcie->appl_base + APPL_CTRL);
-		data &= ~APPL_CTRL_LTSSM_EN;
-		writel(data, pcie->appl_base + APPL_CTRL);
-
 		err = readl_poll_timeout(pcie->appl_base + APPL_DEBUG, data,
 			((data & APPL_DEBUG_LTSSM_STATE_MASK) == LTSSM_STATE_DETECT_QUIET) ||
 			((data & APPL_DEBUG_LTSSM_STATE_MASK) == LTSSM_STATE_DETECT_ACT) ||
@@ -1610,6 +1602,14 @@ static void tegra_pcie_dw_pme_turnoff(struct tegra_pcie_dw *pcie)
 			LTSSM_DELAY_US, LTSSM_TIMEOUT_US);
 		if (err)
 			dev_info(pcie->dev, "LTSSM state: 0x%x detect timeout: %d\n", data, err);
+
+		/*
+		 * Deassert LTSSM state to stop the state toggling between
+		 * polling and detect.
+		 */
+		data = readl(pcie->appl_base + APPL_CTRL);
+		data &= ~APPL_CTRL_LTSSM_EN;
+		writel(data, pcie->appl_base + APPL_CTRL);
 	}
 	/*
 	 * DBI registers may not be accessible after this as PLL-E would be
@@ -1683,11 +1683,6 @@ static void pex_ep_event_pex_rst_assert(struct tegra_pcie_dw *pcie)
 	if (pcie->ep_state == EP_STATE_DISABLED)
 		return;
 
-	/* Disable LTSSM */
-	val = appl_readl(pcie, APPL_CTRL);
-	val &= ~APPL_CTRL_LTSSM_EN;
-	appl_writel(pcie, val, APPL_CTRL);
-
 	ret = readl_poll_timeout(pcie->appl_base + APPL_DEBUG, val,
 		((val & APPL_DEBUG_LTSSM_STATE_MASK) == LTSSM_STATE_DETECT_QUIET) ||
 		((val & APPL_DEBUG_LTSSM_STATE_MASK) == LTSSM_STATE_DETECT_ACT) ||
@@ -1698,6 +1693,14 @@ static void pex_ep_event_pex_rst_assert(struct tegra_pcie_dw *pcie)
 	if (ret)
 		dev_info(pcie->dev, "LTSSM state: 0x%x detect timeout: %d\n", val, ret);
 
+	/*
+	 * Deassert LTSSM state to stop the state toggling between
+	 * polling and detect.
+	 */
+	val = appl_readl(pcie, APPL_CTRL);
+	val &= ~APPL_CTRL_LTSSM_EN;
+	appl_writel(pcie, val, APPL_CTRL);
+
 	reset_control_assert(pcie->core_rst);
 
 	tegra_pcie_disable_phy(pcie);
-- 
2.34.1