linux-kernel - [PATCH V3 06/21] PCI: tegra194: Refactor LTSSM state polling on surprise down

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Message-ID: <20221013183854.21087-7-vidyas@nvidia.com>
Date:   Fri, 14 Oct 2022 00:08:39 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     <lpieralisi@...nel.org>, <robh@...nel.org>, <kw@...ux.com>,
        <bhelgaas@...gle.com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <kishon@...com>, <vkoul@...nel.org>,
        <mani@...nel.org>, <Sergey.Semin@...kalelectronics.ru>,
        <ffclaire1224@...il.com>
CC:     <linux-pci@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-phy@...ts.infradead.org>,
        <kthota@...dia.com>, <mmaddireddy@...dia.com>, <vidyas@...dia.com>,
        <sagar.tv@...il.com>
Subject: [PATCH V3 06/21] PCI: tegra194: Refactor LTSSM state polling on surprise down

On surprise down, LTSSM state transits from L0 -> Recovery.RcvrLock ->
Recovery.RcvrSpeed -> Gen1 Recovery.RcvrLock -> Detect. Recovery.RcvrLock
and Recovery.RcvrSpeed transit times are 24 msec and 48 msec respectively.
So, the total time taken to transit from L0 to detect state is ~96 msec.
Hence, increase the poll time to 120 msec.

Disable the LTSSM state after it transits to detect to avoid LTSSM
toggling between polling and detect states.

tegra_pcie_dw_pme_turnoff() function is called in non-atomic context
only, so use the non-atomic poll function.

Signed-off-by: Vidya Sagar <vidyas@...dia.com>
---
V3:
* Addressed review comments from Bjorn
* Reworded the commit message

V2:
* None

 drivers/pci/controller/dwc/pcie-tegra194.c | 55 +++++++++++++---------
 1 file changed, 32 insertions(+), 23 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
index 69e11a74a0d7..897e2a22bcd3 100644
--- a/drivers/pci/controller/dwc/pcie-tegra194.c
+++ b/drivers/pci/controller/dwc/pcie-tegra194.c
@@ -141,7 +141,11 @@
 #define APPL_DEBUG_PM_LINKST_IN_L0		0x11
 #define APPL_DEBUG_LTSSM_STATE_MASK		GENMASK(8, 3)
 #define APPL_DEBUG_LTSSM_STATE_SHIFT		3
-#define LTSSM_STATE_PRE_DETECT			5
+#define LTSSM_STATE_DETECT_QUIET		0x00
+#define LTSSM_STATE_DETECT_ACT			0x08
+#define LTSSM_STATE_PRE_DETECT_QUIET		0x28
+#define LTSSM_STATE_DETECT_WAIT			0x30
+#define LTSSM_STATE_L2_IDLE			0xa8
 
 #define APPL_RADM_STATUS			0xE4
 #define APPL_PM_XMT_TURNOFF_STATE		BIT(0)
@@ -210,7 +214,8 @@
 #define PME_ACK_DELAY		100   /* 100 us */
 #define PME_ACK_TIMEOUT		10000 /* 10 ms */
 
-#define LTSSM_TIMEOUT 50000	/* 50ms */
+#define LTSSM_DELAY		10000	/* 10 ms */
+#define LTSSM_TIMEOUT		120000	/* 120 ms */
 
 #define GEN3_GEN4_EQ_PRESET_INIT	5
 
@@ -1663,23 +1668,22 @@ static void tegra_pcie_dw_pme_turnoff(struct tegra_pcie_dw *pcie)
 		data &= ~APPL_PINMUX_PEX_RST;
 		appl_writel(pcie, data, APPL_PINMUX);
 
+		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) ||
+			((data & APPL_DEBUG_LTSSM_STATE_MASK) == LTSSM_STATE_PRE_DETECT_QUIET) ||
+			((data & APPL_DEBUG_LTSSM_STATE_MASK) == LTSSM_STATE_DETECT_WAIT),
+			LTSSM_DELAY, LTSSM_TIMEOUT);
+		if (err)
+			dev_info(pcie->dev, "Link didn't go to detect state\n");
+
 		/*
-		 * Some cards do not go to detect state even after de-asserting
-		 * PERST#. So, de-assert LTSSM to bring link to detect state.
+		 * 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);
-
-		err = readl_poll_timeout_atomic(pcie->appl_base + APPL_DEBUG,
-						data,
-						((data &
-						APPL_DEBUG_LTSSM_STATE_MASK) >>
-						APPL_DEBUG_LTSSM_STATE_SHIFT) ==
-						LTSSM_STATE_PRE_DETECT,
-						1, LTSSM_TIMEOUT);
-		if (err)
-			dev_info(pcie->dev, "Link didn't go to detect state\n");
 	}
 	/*
 	 * DBI registers may not be accessible after this as PLL-E would be
@@ -1769,19 +1773,24 @@ static void pex_ep_event_pex_rst_assert(struct tegra_pcie_dw *pcie)
 	if (pcie->ep_state == EP_STATE_DISABLED)
 		return;
 
-	/* Disable LTSSM */
+	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) ||
+		((val & APPL_DEBUG_LTSSM_STATE_MASK) == LTSSM_STATE_PRE_DETECT_QUIET) ||
+		((val & APPL_DEBUG_LTSSM_STATE_MASK) == LTSSM_STATE_DETECT_WAIT) ||
+		((val & APPL_DEBUG_LTSSM_STATE_MASK) == LTSSM_STATE_L2_IDLE),
+		LTSSM_DELAY, LTSSM_TIMEOUT);
+	if (ret)
+		dev_err(pcie->dev, "LTSSM state: 0x%x 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);
 
-	ret = readl_poll_timeout(pcie->appl_base + APPL_DEBUG, val,
-				 ((val & APPL_DEBUG_LTSSM_STATE_MASK) >>
-				 APPL_DEBUG_LTSSM_STATE_SHIFT) ==
-				 LTSSM_STATE_PRE_DETECT,
-				 1, LTSSM_TIMEOUT);
-	if (ret)
-		dev_err(pcie->dev, "Failed to go Detect state: %d\n", ret);
-
 	reset_control_assert(pcie->core_rst);
 
 	tegra_pcie_disable_phy(pcie);
-- 
2.17.1