[PATCH v2] PCI: dwc: Add support to add GEN3 related equalization quirks

[Pankaj Dubey]

From: Anvesh Salveru <anvesh.s@xxxxxxxxxxx>

In some platforms, PCIe PHY may have issues which will prevent linkup
to happen in GEN3 or higher speed. In case equalization fails, link will
fallback to GEN1.

DesignWare controller gives flexibility to disable GEN3 equalization
completely or only phase 2 and 3 of equalization.

This patch enables the DesignWare driver to disable the PCIe GEN3
equalization by enabling one of the following quirks:
 - DWC_EQUALIZATION_DISABLE: To disable GEN3 equalization all phases
 - DWC_EQ_PHASE_2_3_DISABLE: To disable GEN3 equalization phase 2 & 3

Platform drivers can set these quirks via "quirk" variable of "dw_pcie"
struct.

Signed-off-by: Anvesh Salveru <anvesh.s@xxxxxxxxxxx>
Signed-off-by: Pankaj Dubey <pankaj.dubey@xxxxxxxxxxx>
---
Patchset v1 can be found at:
 - 1/2: https://lkml.org/lkml/2019/9/10/443
 - 2/2: https://lkml.org/lkml/2019/9/10/444

Changes w.r.t v1:
 - Squashed two patches from v1 into one as suggested by Gustavo
 - Addressed review comments from Andrew

 drivers/pci/controller/dwc/pcie-designware.c | 12 ++++++++++++
 drivers/pci/controller/dwc/pcie-designware.h |  9 +++++++++
 2 files changed, 21 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 7d25102..97fb18d 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -466,4 +466,16 @@ void dw_pcie_setup(struct dw_pcie *pci)
 		break;
 	}
 	dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, val);
+
+	if (pci->quirk & DWC_EQUALIZATION_DISABLE) {
+		val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
+		val |= PORT_LOGIC_GEN3_EQ_DISABLE;
+		dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
+	}
+
+	if (pci->quirk & DWC_EQ_PHASE_2_3_DISABLE) {
+		val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED);
+		val |= PORT_LOGIC_GEN3_EQ_PHASE_2_3_DISABLE;
+		dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val);
+	}
 }
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index ffed084..e428b62 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -29,6 +29,10 @@
 #define LINK_WAIT_MAX_IATU_RETRIES	5
 #define LINK_WAIT_IATU			9
 
+/* Parameters for GEN3 related quirks */
+#define DWC_EQUALIZATION_DISABLE	BIT(1)
+#define DWC_EQ_PHASE_2_3_DISABLE	BIT(2)
+
 /* Synopsys-specific PCIe configuration registers */
 #define PCIE_PORT_LINK_CONTROL		0x710
 #define PORT_LINK_MODE_MASK		GENMASK(21, 16)
@@ -60,6 +64,10 @@
 #define PCIE_MSI_INTR0_MASK		0x82C
 #define PCIE_MSI_INTR0_STATUS		0x830
 
+#define PCIE_PORT_GEN3_RELATED		0x890
+#define PORT_LOGIC_GEN3_EQ_PHASE_2_3_DISABLE	BIT(9)
+#define PORT_LOGIC_GEN3_EQ_DISABLE		BIT(16)
+
 #define PCIE_ATU_VIEWPORT		0x900
 #define PCIE_ATU_REGION_INBOUND		BIT(31)
 #define PCIE_ATU_REGION_OUTBOUND	0
@@ -244,6 +252,7 @@ struct dw_pcie {
 	struct dw_pcie_ep	ep;
 	const struct dw_pcie_ops *ops;
 	unsigned int		version;
+	unsigned int		quirk;
 };
 
 #define to_dw_pcie_from_pp(port) container_of((port), struct dw_pcie, pp)
-- 
2.7.4