linux-kernel - [PATCH] PCI: Cadence: Add quirk for Gen2 controller to do autonomous speed change.

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Message-ID: <20200918103429.4769-1-nadeem@cadence.com>
Date:   Fri, 18 Sep 2020 12:34:29 +0200
From:   Nadeem Athani <nadeem@...ence.com>
To:     <tjoseph@...ence.com>, <lorenzo.pieralisi@....com>,
        <robh@...nel.org>, <bhelgaas@...gle.com>,
        <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <nadeem@...ence.com>, <mparab@...ence.com>, <sjakhade@...ence.com>
Subject: [PATCH] PCI: Cadence: Add quirk for Gen2 controller to do autonomous speed change.

Cadence controller will not initiate autonomous speed change if
strapped as Gen2. The Retrain bit is set as a quirk to trigger
this speed change.

Signed-off-by: Nadeem Athani <nadeem@...ence.com>
---
 drivers/pci/controller/cadence/pcie-cadence-host.c |   13 +++++++++++++
 drivers/pci/controller/cadence/pcie-cadence.h      |    6 ++++++
 2 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c b/drivers/pci/controller/cadence/pcie-cadence-host.c
index 4550e0d..4cb7f29 100644
--- a/drivers/pci/controller/cadence/pcie-cadence-host.c
+++ b/drivers/pci/controller/cadence/pcie-cadence-host.c
@@ -83,6 +83,8 @@ static int cdns_pcie_host_init_root_port(struct cdns_pcie_rc *rc)
 	struct cdns_pcie *pcie = &rc->pcie;
 	u32 value, ctrl;
 	u32 id;
+	u32 link_cap = CDNS_PCIE_LINK_CAP_OFFSET;
+	u8 sls, lnk_ctl;
 
 	/*
 	 * Set the root complex BAR configuration register:
@@ -111,6 +113,17 @@ static int cdns_pcie_host_init_root_port(struct cdns_pcie_rc *rc)
 	if (rc->device_id != 0xffff)
 		cdns_pcie_rp_writew(pcie, PCI_DEVICE_ID, rc->device_id);
 
+	/* Quirk to enable autonomous speed change for GEN2 controller */
+	/* Reading Supported Link Speed value */
+	sls = PCI_EXP_LNKCAP_SLS &
+		cdns_pcie_rp_readb(pcie, link_cap + PCI_EXP_LNKCAP);
+	if (sls == PCI_EXP_LNKCAP_SLS_5_0GB) {
+		/* Since this a Gen2 controller, set Retrain Link(RL) bit */
+		lnk_ctl = cdns_pcie_rp_readb(pcie, link_cap + PCI_EXP_LNKCTL);
+		lnk_ctl |= PCI_EXP_LNKCTL_RL;
+		cdns_pcie_rp_writeb(pcie, link_cap + PCI_EXP_LNKCTL, lnk_ctl);
+	}
+
 	cdns_pcie_rp_writeb(pcie, PCI_CLASS_REVISION, 0);
 	cdns_pcie_rp_writeb(pcie, PCI_CLASS_PROG, 0);
 	cdns_pcie_rp_writew(pcie, PCI_CLASS_DEVICE, PCI_CLASS_BRIDGE_PCI);
diff --git a/drivers/pci/controller/cadence/pcie-cadence.h b/drivers/pci/controller/cadence/pcie-cadence.h
index feed1e3..075c263 100644
--- a/drivers/pci/controller/cadence/pcie-cadence.h
+++ b/drivers/pci/controller/cadence/pcie-cadence.h
@@ -120,6 +120,7 @@
  */
 #define CDNS_PCIE_RP_BASE	0x00200000
 
+#define CDNS_PCIE_LINK_CAP_OFFSET 0xC0
 
 /*
  * Address Translation Registers
@@ -413,6 +414,11 @@ static inline void cdns_pcie_rp_writew(struct cdns_pcie *pcie,
 	cdns_pcie_write_sz(addr, 0x2, value);
 }
 
+static inline u8 cdns_pcie_rp_readb(struct cdns_pcie *pcie, u32 reg)
+{
+	return readb(pcie->reg_base + CDNS_PCIE_RP_BASE + reg);
+}
+
 /* Endpoint Function register access */
 static inline void cdns_pcie_ep_fn_writeb(struct cdns_pcie *pcie, u8 fn,
 					  u32 reg, u8 value)
-- 
1.7.1