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Subject[PATCH AUTOSEL 5.10 35/47] PCI: cadence: Retrain Link to work around Gen2 training defect
Date
From: Nadeem Athani <nadeem@cadence.com>

[ Upstream commit 4740b969aaf58adeca6829947a3ad8da423976cf ]

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

Link: https://lore.kernel.org/r/20210209144622.26683-3-nadeem@cadence.com
Signed-off-by: Nadeem Athani <nadeem@cadence.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/pci/controller/cadence/pci-j721e.c | 3 +
.../controller/cadence/pcie-cadence-host.c | 81 ++++++++++++++-----
drivers/pci/controller/cadence/pcie-cadence.h | 11 ++-
3 files changed, 76 insertions(+), 19 deletions(-)

diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c
index 586b9d69fa5e..d34ca0fda0f6 100644
--- a/drivers/pci/controller/cadence/pci-j721e.c
+++ b/drivers/pci/controller/cadence/pci-j721e.c
@@ -63,6 +63,7 @@ enum j721e_pcie_mode {

struct j721e_pcie_data {
enum j721e_pcie_mode mode;
+ bool quirk_retrain_flag;
};

static inline u32 j721e_pcie_user_readl(struct j721e_pcie *pcie, u32 offset)
@@ -270,6 +271,7 @@ static struct pci_ops cdns_ti_pcie_host_ops = {

static const struct j721e_pcie_data j721e_pcie_rc_data = {
.mode = PCI_MODE_RC,
+ .quirk_retrain_flag = true,
};

static const struct j721e_pcie_data j721e_pcie_ep_data = {
@@ -378,6 +380,7 @@ static int j721e_pcie_probe(struct platform_device *pdev)

bridge->ops = &cdns_ti_pcie_host_ops;
rc = pci_host_bridge_priv(bridge);
+ rc->quirk_retrain_flag = data->quirk_retrain_flag;

cdns_pcie = &rc->pcie;
cdns_pcie->dev = dev;
diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c b/drivers/pci/controller/cadence/pcie-cadence-host.c
index 811c1cb2e8de..6f591d382578 100644
--- a/drivers/pci/controller/cadence/pcie-cadence-host.c
+++ b/drivers/pci/controller/cadence/pcie-cadence-host.c
@@ -77,6 +77,68 @@ static struct pci_ops cdns_pcie_host_ops = {
.write = pci_generic_config_write,
};

+static int cdns_pcie_host_wait_for_link(struct cdns_pcie *pcie)
+{
+ struct device *dev = pcie->dev;
+ int retries;
+
+ /* Check if the link is up or not */
+ for (retries = 0; retries < LINK_WAIT_MAX_RETRIES; retries++) {
+ if (cdns_pcie_link_up(pcie)) {
+ dev_info(dev, "Link up\n");
+ return 0;
+ }
+ usleep_range(LINK_WAIT_USLEEP_MIN, LINK_WAIT_USLEEP_MAX);
+ }
+
+ return -ETIMEDOUT;
+}
+
+static int cdns_pcie_retrain(struct cdns_pcie *pcie)
+{
+ u32 lnk_cap_sls, pcie_cap_off = CDNS_PCIE_RP_CAP_OFFSET;
+ u16 lnk_stat, lnk_ctl;
+ int ret = 0;
+
+ /*
+ * Set retrain bit if current speed is 2.5 GB/s,
+ * but the PCIe root port support is > 2.5 GB/s.
+ */
+
+ lnk_cap_sls = cdns_pcie_readl(pcie, (CDNS_PCIE_RP_BASE + pcie_cap_off +
+ PCI_EXP_LNKCAP));
+ if ((lnk_cap_sls & PCI_EXP_LNKCAP_SLS) <= PCI_EXP_LNKCAP_SLS_2_5GB)
+ return ret;
+
+ lnk_stat = cdns_pcie_rp_readw(pcie, pcie_cap_off + PCI_EXP_LNKSTA);
+ if ((lnk_stat & PCI_EXP_LNKSTA_CLS) == PCI_EXP_LNKSTA_CLS_2_5GB) {
+ lnk_ctl = cdns_pcie_rp_readw(pcie,
+ pcie_cap_off + PCI_EXP_LNKCTL);
+ lnk_ctl |= PCI_EXP_LNKCTL_RL;
+ cdns_pcie_rp_writew(pcie, pcie_cap_off + PCI_EXP_LNKCTL,
+ lnk_ctl);
+
+ ret = cdns_pcie_host_wait_for_link(pcie);
+ }
+ return ret;
+}
+
+static int cdns_pcie_host_start_link(struct cdns_pcie_rc *rc)
+{
+ struct cdns_pcie *pcie = &rc->pcie;
+ int ret;
+
+ ret = cdns_pcie_host_wait_for_link(pcie);
+
+ /*
+ * Retrain link for Gen2 training defect
+ * if quirk flag is set.
+ */
+ if (!ret && rc->quirk_retrain_flag)
+ ret = cdns_pcie_retrain(pcie);
+
+ return ret;
+}

static int cdns_pcie_host_init_root_port(struct cdns_pcie_rc *rc)
{
@@ -398,23 +460,6 @@ static int cdns_pcie_host_init(struct device *dev,
return cdns_pcie_host_init_address_translation(rc);
}

-static int cdns_pcie_host_wait_for_link(struct cdns_pcie *pcie)
-{
- struct device *dev = pcie->dev;
- int retries;
-
- /* Check if the link is up or not */
- for (retries = 0; retries < LINK_WAIT_MAX_RETRIES; retries++) {
- if (cdns_pcie_link_up(pcie)) {
- dev_info(dev, "Link up\n");
- return 0;
- }
- usleep_range(LINK_WAIT_USLEEP_MIN, LINK_WAIT_USLEEP_MAX);
- }
-
- return -ETIMEDOUT;
-}
-
int cdns_pcie_host_setup(struct cdns_pcie_rc *rc)
{
struct device *dev = rc->pcie.dev;
@@ -457,7 +502,7 @@ int cdns_pcie_host_setup(struct cdns_pcie_rc *rc)
return ret;
}

- ret = cdns_pcie_host_wait_for_link(pcie);
+ ret = cdns_pcie_host_start_link(rc);
if (ret)
dev_dbg(dev, "PCIe link never came up\n");

diff --git a/drivers/pci/controller/cadence/pcie-cadence.h b/drivers/pci/controller/cadence/pcie-cadence.h
index feed1e3038f4..6705a5fedfbb 100644
--- a/drivers/pci/controller/cadence/pcie-cadence.h
+++ b/drivers/pci/controller/cadence/pcie-cadence.h
@@ -119,7 +119,7 @@
* Root Port Registers (PCI configuration space for the root port function)
*/
#define CDNS_PCIE_RP_BASE 0x00200000
-
+#define CDNS_PCIE_RP_CAP_OFFSET 0xc0

/*
* Address Translation Registers
@@ -290,6 +290,7 @@ struct cdns_pcie {
* @device_id: PCI device ID
* @avail_ib_bar: Satus of RP_BAR0, RP_BAR1 and RP_NO_BAR if it's free or
* available
+ * @quirk_retrain_flag: Retrain link as quirk for PCIe Gen2
*/
struct cdns_pcie_rc {
struct cdns_pcie pcie;
@@ -298,6 +299,7 @@ struct cdns_pcie_rc {
u32 vendor_id;
u32 device_id;
bool avail_ib_bar[CDNS_PCIE_RP_MAX_IB];
+ bool quirk_retrain_flag;
};

/**
@@ -413,6 +415,13 @@ static inline void cdns_pcie_rp_writew(struct cdns_pcie *pcie,
cdns_pcie_write_sz(addr, 0x2, value);
}

+static inline u16 cdns_pcie_rp_readw(struct cdns_pcie *pcie, u32 reg)
+{
+ void __iomem *addr = pcie->reg_base + CDNS_PCIE_RP_BASE + reg;
+
+ return cdns_pcie_read_sz(addr, 0x2);
+}
+
/* Endpoint Function register access */
static inline void cdns_pcie_ep_fn_writeb(struct cdns_pcie *pcie, u8 fn,
u32 reg, u8 value)
--
2.30.1
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