linux-kernel - [PATCH V2 3/9] PCI: tegra194: Fix polling delay for L2 state

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Message-ID: <20220926115038.24727-4-vidyas@nvidia.com>
Date:   Mon, 26 Sep 2022 17:20:32 +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 V2 3/9] PCI: tegra194: Fix polling delay for L2 state

Current L2 state polling with 1us interval is too aggressive. Based on
the experiments with different endpoints, LTSSM state transisition to L2
is happening between 6us ~ 40us. Hence, update the polling delay for L2
state from 1us to 100us for a better utilization of CPU cycles.

Fixes: 56e15a238d92 ("PCI: tegra: Add Tegra194 PCIe support")
Signed-off-by: Vidya Sagar <vidyas@...dia.com>
---
V2:
* None

 drivers/pci/controller/dwc/pcie-tegra194.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
index 7721f920dd74..7d6e54a12eff 100644
--- a/drivers/pci/controller/dwc/pcie-tegra194.c
+++ b/drivers/pci/controller/dwc/pcie-tegra194.c
@@ -206,7 +206,8 @@
 #define CAP_SPCIE_CAP_OFF_USP_TX_PRESET0_MASK	GENMASK(11, 8)
 #define CAP_SPCIE_CAP_OFF_USP_TX_PRESET0_SHIFT	8
 
-#define PME_ACK_TIMEOUT 10000
+#define PME_ACK_DELAY		100   /* 100 us */
+#define PME_ACK_TIMEOUT		10000 /* 10 ms */
 
 #define LTSSM_TIMEOUT 50000	/* 50ms */
 
@@ -1556,7 +1557,7 @@ static int tegra_pcie_try_link_l2(struct tegra_pcie_dw *pcie)
 
 	return readl_poll_timeout_atomic(pcie->appl_base + APPL_DEBUG, val,
 				 val & APPL_DEBUG_PM_LINKST_IN_L2_LAT,
-				 1, PME_ACK_TIMEOUT);
+				 PME_ACK_DELAY, PME_ACK_TIMEOUT);
 }
 
 static void tegra_pcie_dw_pme_turnoff(struct tegra_pcie_dw *pcie)
-- 
2.17.1