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Message-ID: <20210426051427.15945-1-nadeem@cadence.com>
Date: Mon, 26 Apr 2021 07:14:27 +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>,
<kishon@...com>, <linux-arm-kernel@...ts.infradead.org>,
<linux-omap@...r.kernel.org>
CC: <nadeem@...ence.com>, <mparab@...ence.com>, <sjakhade@...ence.com>,
<pthombar@...ence.com>
Subject: [PATCH] PCI: cadence: Set LTSSM Detect Quiet state minimum delay as workaround for training defect.
Adding a quirk flag "quirk_detect_quiet_flag" to program the minimum
time that LTSSM waits on entering Detect.Quiet state.
Setting this to 2ms for specific TI j7200 SOC as a workaround to resolve
a link training issue in IP.
In future revisions this setting will not be required.
As per PCIe specification, all Receivers must meet the Z-RX-DC
specification for 2.5 GT/s within 1ms of entering Detect.Quiet LTSSM
substate. The LTSSM must stay in this substate until the ZRXDC
specification for 2.5 GT/s is met.
00 : 0 minimum wait time in Detect.Quiet state.
01 : 100us minimum wait time in Detect.Quiet state.
10 : 1ms minimum wait time in Detect.Quiet state.
11 : 2ms minimum wait time in Detect.Quiet state.
Signed-off-by: Nadeem Athani <nadeem@...ence.com>
---
drivers/pci/controller/cadence/pcie-cadence-ep.c | 21 +++++++++++++++++++++
drivers/pci/controller/cadence/pcie-cadence-host.c | 21 +++++++++++++++++++++
drivers/pci/controller/cadence/pcie-cadence.h | 12 ++++++++++++
3 files changed, 54 insertions(+)
diff --git a/drivers/pci/controller/cadence/pcie-cadence-ep.c b/drivers/pci/controller/cadence/pcie-cadence-ep.c
index 897cdde02bd8..245771f03c21 100644
--- a/drivers/pci/controller/cadence/pcie-cadence-ep.c
+++ b/drivers/pci/controller/cadence/pcie-cadence-ep.c
@@ -552,6 +552,23 @@ static const struct pci_epc_ops cdns_pcie_epc_ops = {
.get_features = cdns_pcie_ep_get_features,
};
+static void cdns_pcie_detect_quiet_min_delay_set(struct cdns_pcie_ep *ep)
+{
+ struct cdns_pcie *pcie = &ep->pcie;
+ u32 delay = 0x3;
+ u32 ltssm_control_cap;
+
+ /*
+ * Set the LTSSM Detect Quiet state min. delay to 2ms.
+ */
+
+ ltssm_control_cap = cdns_pcie_readl(pcie, CDNS_PCIE_LTSSM_CONTROL_CAP);
+ ltssm_control_cap = ((ltssm_control_cap &
+ ~CDNS_PCIE_DETECT_QUIET_MIN_DELAY_MASK) |
+ CDNS_PCIE_DETECT_QUIET_MIN_DELAY(delay));
+
+ cdns_pcie_writel(pcie, CDNS_PCIE_LTSSM_CONTROL_CAP, ltssm_control_cap);
+}
int cdns_pcie_ep_setup(struct cdns_pcie_ep *ep)
{
@@ -623,6 +640,10 @@ int cdns_pcie_ep_setup(struct cdns_pcie_ep *ep)
ep->irq_pci_addr = CDNS_PCIE_EP_IRQ_PCI_ADDR_NONE;
/* Reserve region 0 for IRQs */
set_bit(0, &ep->ob_region_map);
+
+ if (ep->quirk_detect_quiet_flag)
+ cdns_pcie_detect_quiet_min_delay_set(ep);
+
spin_lock_init(&ep->lock);
return 0;
diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c b/drivers/pci/controller/cadence/pcie-cadence-host.c
index ae1c55503513..ffc2dbeb1240 100644
--- a/drivers/pci/controller/cadence/pcie-cadence-host.c
+++ b/drivers/pci/controller/cadence/pcie-cadence-host.c
@@ -462,6 +462,24 @@ static int cdns_pcie_host_init(struct device *dev,
return cdns_pcie_host_init_address_translation(rc);
}
+static void cdns_pcie_detect_quiet_min_delay_set(struct cdns_pcie_rc *rc)
+{
+ struct cdns_pcie *pcie = &rc->pcie;
+ u32 delay = 0x3;
+ u32 ltssm_control_cap;
+
+ /*
+ * Set the LTSSM Detect Quiet state min. delay to 2ms.
+ */
+
+ ltssm_control_cap = cdns_pcie_readl(pcie, CDNS_PCIE_LTSSM_CONTROL_CAP);
+ ltssm_control_cap = ((ltssm_control_cap &
+ ~CDNS_PCIE_DETECT_QUIET_MIN_DELAY_MASK) |
+ CDNS_PCIE_DETECT_QUIET_MIN_DELAY(delay));
+
+ cdns_pcie_writel(pcie, CDNS_PCIE_LTSSM_CONTROL_CAP, ltssm_control_cap);
+}
+
int cdns_pcie_host_setup(struct cdns_pcie_rc *rc)
{
struct device *dev = rc->pcie.dev;
@@ -498,6 +516,9 @@ int cdns_pcie_host_setup(struct cdns_pcie_rc *rc)
return PTR_ERR(rc->cfg_base);
rc->cfg_res = res;
+ if (rc->quirk_detect_quiet_flag)
+ cdns_pcie_detect_quiet_min_delay_set(rc);
+
ret = cdns_pcie_start_link(pcie);
if (ret) {
dev_err(dev, "Failed to start link\n");
diff --git a/drivers/pci/controller/cadence/pcie-cadence.h b/drivers/pci/controller/cadence/pcie-cadence.h
index 254d2570f8c9..d074475fe887 100644
--- a/drivers/pci/controller/cadence/pcie-cadence.h
+++ b/drivers/pci/controller/cadence/pcie-cadence.h
@@ -189,6 +189,14 @@
/* AXI link down register */
#define CDNS_PCIE_AT_LINKDOWN (CDNS_PCIE_AT_BASE + 0x0824)
+/* LTSSM Capabilities register */
+#define CDNS_PCIE_LTSSM_CONTROL_CAP (CDNS_PCIE_LM_BASE + 0x0054)
+#define CDNS_PCIE_DETECT_QUIET_MIN_DELAY_MASK GENMASK(2, 1)
+#define CDNS_PCIE_DETECT_QUIET_MIN_DELAY_SHIFT 1
+#define CDNS_PCIE_DETECT_QUIET_MIN_DELAY(delay) \
+ (((delay) << CDNS_PCIE_DETECT_QUIET_MIN_DELAY_SHIFT) & \
+ CDNS_PCIE_DETECT_QUIET_MIN_DELAY_MASK)
+
enum cdns_pcie_rp_bar {
RP_BAR_UNDEFINED = -1,
RP_BAR0,
@@ -292,6 +300,7 @@ struct cdns_pcie {
* @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
+ * @quirk_detect_quiet_flag: LTSSM Detect Quiet min delay set as quirk
*/
struct cdns_pcie_rc {
struct cdns_pcie pcie;
@@ -301,6 +310,7 @@ struct cdns_pcie_rc {
u32 device_id;
bool avail_ib_bar[CDNS_PCIE_RP_MAX_IB];
bool quirk_retrain_flag;
+ bool quirk_detect_quiet_flag;
};
/**
@@ -331,6 +341,7 @@ struct cdns_pcie_epf {
* registers fields (RMW) accessible by both remote RC and EP to
* minimize time between read and write
* @epf: Structure to hold info about endpoint function
+ * @quirk_detect_quiet_flag: LTSSM Detect Quiet min delay set as quirk
*/
struct cdns_pcie_ep {
struct cdns_pcie pcie;
@@ -345,6 +356,7 @@ struct cdns_pcie_ep {
/* protect writing to PCI_STATUS while raising legacy interrupts */
spinlock_t lock;
struct cdns_pcie_epf *epf;
+ bool quirk_detect_quiet_flag;
};
--
2.15.0
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