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

Vidya Sagar
2022-10-13T18:42:47Z

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@nvidia.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