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From: Manikanta Maddireddy <mmaddireddy@nvidia.com>
To: <thierry.reding@gmail.com>, <bhelgaas@google.com>,
	<robh+dt@kernel.org>, <mark.rutland@arm.com>,
	<jonathanh@nvidia.com>, <lorenzo.pieralisi@arm.com>,
	<vidyas@nvidia.com>
Cc: <linux-tegra@vger.kernel.org>, <linux-pci@vger.kernel.org>,
	<devicetree@vger.kernel.org>,
	Manikanta Maddireddy <mmaddireddy@nvidia.com>
Subject: [PATCH V5 16/27] PCI: tegra: Set target speed as Gen1 before starting LTSSM
Date: Mon, 17 Jun 2019 23:09:41 +0530
Message-ID: <20190617173952.29363-17-mmaddireddy@nvidia.com> (raw)
In-Reply-To: <20190617173952.29363-1-mmaddireddy@nvidia.com>

PCIe link up fails with few legacy endpoints if root port advertises both
Gen-1 and Gen-2 speeds in Tegra. This is because link number negotiation
fails if both Gen1 & Gen2 are advertised. Tegra doesn't retry link up by
advertising only Gen1. Hence, the strategy followed here is to initially
advertise only Gen-1 and after link is up, retrain link to Gen-2 speed.

Tegra doesn't support HW autonomous speed change. Link comes up in Gen1
even if Gen2 is advertised, so there is no downside of this change.

This behavior is observed with following two PCIe devices on Tegra,
 - Fusion HDTV 5 Express card
 - IOGear SIL - PCIE - SATA card

Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
---
V5: No change

V4: No change

V3: No change

V2: Updated commit log to reflect why this issue is observed on Tegra with
these particular cards

 drivers/pci/controller/pci-tegra.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/pci/controller/pci-tegra.c b/drivers/pci/controller/pci-tegra.c
index 6ed406c46409..abb94595c76b 100644
--- a/drivers/pci/controller/pci-tegra.c
+++ b/drivers/pci/controller/pci-tegra.c
@@ -676,6 +676,17 @@ static void tegra_pcie_apply_sw_fixup(struct tegra_pcie_port *port)
 		value |= soc->update_fc_threshold;
 		writel(value, port->base + RP_VEND_XP);
 	}
+
+	/*
+	 * PCIe link doesn't come up with few legacy PCIe endpoints if
+	 * root port advertises both Gen-1 and Gen-2 speeds in Tegra.
+	 * Hence, the strategy followed here is to initially advertise
+	 * only Gen-1 and after link is up, retrain link to Gen-2 speed
+	 */
+	value = readl(port->base + RP_LINK_CONTROL_STATUS_2);
+	value &= ~PCI_EXP_LNKSTA_CLS;
+	value |= PCI_EXP_LNKSTA_CLS_2_5GB;
+	writel(value, port->base + RP_LINK_CONTROL_STATUS_2);
 }
 
 static void tegra_pcie_port_enable(struct tegra_pcie_port *port)
-- 
2.17.1


  parent reply index

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-17 17:39 [PATCH V5 00/27] Enable Tegra PCIe root port features Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 01/27] soc/tegra: pmc: Export tegra_powergate_power_on() Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 02/27] PCI: tegra: Handle failure cases in tegra_pcie_power_on() Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 03/27] PCI: tegra: Rearrange Tegra PCIe driver functions Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 04/27] PCI: tegra: Mask AFI_INTR in runtime suspend Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 05/27] PCI: tegra: Fix PCIe host power up sequence Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 06/27] PCI: tegra: Add PCIe Gen2 link speed support Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 07/27] PCI: tegra: Advertise PCIe Advanced Error Reporting (AER) capability Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 08/27] PCI: tegra: Program UPHY electrical settings for Tegra210 Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 09/27] PCI: tegra: Enable opportunistic UpdateFC and ACK Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 10/27] PCI: tegra: Disable AFI dynamic clock gating Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 11/27] PCI: tegra: Process pending DLL transactions before entering L1 or L2 Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 12/27] PCI: tegra: Enable PCIe xclk clock clamping Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 13/27] PCI: tegra: Increase the deskew retry time Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 14/27] PCI: tegra: Add SW fixup for RAW violations Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 15/27] PCI: tegra: Update flow control timer frequency in Tegra210 Manikanta Maddireddy
2019-06-17 17:39 ` Manikanta Maddireddy [this message]
2019-06-17 17:39 ` [PATCH V5 17/27] PCI: tegra: Fix PLLE power down issue due to CLKREQ# signal Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 18/27] PCI: tegra: Program AFI_CACHE* registers only for Tegra20 Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 19/27] PCI: tegra: Change PRSNT_SENSE IRQ log to debug Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 20/27] PCI: tegra: Use legacy IRQ for port service drivers Manikanta Maddireddy
2019-06-18  5:47   ` Manikanta Maddireddy
2019-06-18 13:35     ` Lorenzo Pieralisi
2019-06-17 17:39 ` [PATCH V5 21/27] PCI: tegra: Add AFI_PEX2_CTRL reg offset as part of soc struct Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 22/27] dt-bindings: pci: tegra: Document PCIe DPD pinctrl optional prop Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 23/27] arm64: tegra: Add PEX DPD states as pinctrl properties Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 24/27] PCI: tegra: Put PEX CLK & BIAS pads in DPD mode Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 25/27] PCI: Add DT binding for "reset-gpios" property Manikanta Maddireddy
2019-06-17 17:39 ` [PATCH V5 26/27] PCI: tegra: Add support for GPIO based PERST# Manikanta Maddireddy
2019-06-18 10:51   ` Thierry Reding
2019-06-17 17:39 ` [PATCH V5 27/27] PCI: tegra: Change link retry log level to debug Manikanta Maddireddy

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