[PATCH 06/15] NTB: BWD Link Recovery

Jon Mason
2013-08-02T17:39:14Z

The BWD NTB device will drop the link if an error is encountered on the
point-to-point PCI bridge. The link will stay down until all errors are
cleared and the link is re-established. On link down, check to see if
the error is detected, if so do the necessary housekeeping to try and
recover from the error and reestablish the link.

There is a potential race between the 2 NTB devices recovering at the
same time. If the times are synchronized, the link will not recover and the
driver will be stuck in this loop forever. Add a random interval to the
recovery time to prevent this race.

Signed-off-by: Jon Mason <jon.mason@intel.com>
---
drivers/ntb/ntb_hw.c | 110 ++++++++++++++++++++++++++++++++++++++++++++++--
drivers/ntb/ntb_hw.h | 5 +++
drivers/ntb/ntb_regs.h | 15 +++++++
3 files changed, 127 insertions(+), 3 deletions(-)

diff --git a/drivers/ntb/ntb_hw.c b/drivers/ntb/ntb_hw.c
index 674bc09..d259d41 100644
--- a/drivers/ntb/ntb_hw.c
+++ b/drivers/ntb/ntb_hw.c
@@ -46,10 +46,12 @@
* Jon Mason <jon.mason@intel.com>
*/
#include <linux/debugfs.h>
+#include <linux/delay.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/pci.h>
+#include <linux/random.h>
#include <linux/slab.h>
#include "ntb_hw.h"
#include "ntb_regs.h"
@@ -84,6 +86,8 @@ enum {

struct dentry *debugfs_dir;

+#define BWD_LINK_RECOVERY_TIME 500
+
/* Translate memory window 0,1 to BAR 2,4 */
#define MW_TO_BAR(mw) (mw * NTB_MAX_NUM_MW + 2)

@@ -425,6 +429,49 @@ void ntb_ring_sdb(struct ntb_device *ndev, unsigned int db)
(db * ndev->bits_per_vector), ndev->reg_ofs.sdb);
}

+static void bwd_recover_link(struct ntb_device *ndev)
+{
+ u32 status;
+
+ /* Driver resets the NTB ModPhy lanes - magic! */
+ writeb(0xe0, ndev->reg_base + BWD_MODPHY_PCSREG6);
+ writeb(0x40, ndev->reg_base + BWD_MODPHY_PCSREG4);
+ writeb(0x60, ndev->reg_base + BWD_MODPHY_PCSREG4);
+ writeb(0x60, ndev->reg_base + BWD_MODPHY_PCSREG6);
+
+ /* Driver waits 100ms to allow the NTB ModPhy to settle */
+ msleep(100);
+
+ /* Clear AER Errors, write to clear */
+ status = readl(ndev->reg_base + BWD_ERRCORSTS_OFFSET);
+ dev_dbg(&ndev->pdev->dev, "ERRCORSTS = %x\n", status);
+ status &= PCI_ERR_COR_REP_ROLL;
+ writel(status, ndev->reg_base + BWD_ERRCORSTS_OFFSET);
+
+ /* Clear unexpected electrical idle event in LTSSM, write to clear */
+ status = readl(ndev->reg_base + BWD_LTSSMERRSTS0_OFFSET);
+ dev_dbg(&ndev->pdev->dev, "LTSSMERRSTS0 = %x\n", status);
+ status |= BWD_LTSSMERRSTS0_UNEXPECTEDEI;
+ writel(status, ndev->reg_base + BWD_LTSSMERRSTS0_OFFSET);
+
+ /* Clear DeSkew Buffer error, write to clear */
+ status = readl(ndev->reg_base + BWD_DESKEWSTS_OFFSET);
+ dev_dbg(&ndev->pdev->dev, "DESKEWSTS = %x\n", status);
+ status |= BWD_DESKEWSTS_DBERR;
+ writel(status, ndev->reg_base + BWD_DESKEWSTS_OFFSET);
+
+ status = readl(ndev->reg_base + BWD_IBSTERRRCRVSTS0_OFFSET);
+ dev_dbg(&ndev->pdev->dev, "IBSTERRRCRVSTS0 = %x\n", status);
+ status &= BWD_IBIST_ERR_OFLOW;
+ writel(status, ndev->reg_base + BWD_IBSTERRRCRVSTS0_OFFSET);
+
+ /* Releases the NTB state machine to allow the link to retrain */
+ status = readl(ndev->reg_base + BWD_LTSSMSTATEJMP_OFFSET);
+ dev_dbg(&ndev->pdev->dev, "LTSSMSTATEJMP = %x\n", status);
+ status &= ~BWD_LTSSMSTATEJMP_FORCEDETECT;
+ writel(status, ndev->reg_base + BWD_LTSSMSTATEJMP_OFFSET);
+}
+
static void ntb_link_event(struct ntb_device *ndev, int link_state)
{
unsigned int event;
@@ -448,13 +495,16 @@ static void ntb_link_event(struct ntb_device *ndev, int link_state)
if (rc)
return;
}
+
+ ndev->link_width = (status & NTB_LINK_WIDTH_MASK) >> 4;
+ ndev->link_speed = (status & NTB_LINK_SPEED_MASK);
dev_info(&ndev->pdev->dev, "Link Width %d, Link Speed %d\n",
- (status & NTB_LINK_WIDTH_MASK) >> 4,
- (status & NTB_LINK_SPEED_MASK));
+ ndev->link_width, ndev->link_speed);
} else {
dev_info(&ndev->pdev->dev, "Link Down\n");
ndev->link_status = NTB_LINK_DOWN;
event = NTB_EVENT_HW_LINK_DOWN;
+ /* Don't modify link width/speed, we need it in link recovery */
}

/* notify the upper layer if we have an event change */
@@ -494,6 +544,47 @@ static int ntb_link_status(struct ntb_device *ndev)
return 0;
}

+static void bwd_link_recovery(struct work_struct *work)
+{
+ struct ntb_device *ndev = container_of(work, struct ntb_device,
+ lr_timer.work);
+ u32 status32;
+
+ bwd_recover_link(ndev);
+ /* There is a potential race between the 2 NTB devices recovering at the
+ * same time. If the times are the same, the link will not recover and
+ * the driver will be stuck in this loop forever. Add a random interval
+ * to the recovery time to prevent this race.
+ */
+ msleep(BWD_LINK_RECOVERY_TIME + prandom_u32() % BWD_LINK_RECOVERY_TIME);
+
+ status32 = readl(ndev->reg_base + BWD_LTSSMSTATEJMP_OFFSET);
+ if (status32 & BWD_LTSSMSTATEJMP_FORCEDETECT)
+ goto retry;
+
+ status32 = readl(ndev->reg_base + BWD_IBSTERRRCRVSTS0_OFFSET);
+ if (status32 & BWD_IBIST_ERR_OFLOW)
+ goto retry;
+
+ status32 = readl(ndev->reg_ofs.lnk_cntl);
+ if (!(status32 & BWD_CNTL_LINK_DOWN)) {
+ unsigned char speed, width;
+ u16 status16;
+
+ status16 = readw(ndev->reg_ofs.lnk_stat);
+ width = (status16 & NTB_LINK_WIDTH_MASK) >> 4;
+ speed = (status16 & NTB_LINK_SPEED_MASK);
+ if (ndev->link_width != width || ndev->link_speed != speed)
+ goto retry;
+ }
+
+ schedule_delayed_work(&ndev->hb_timer, NTB_HB_TIMEOUT);
+ return;
+
+retry:
+ schedule_delayed_work(&ndev->lr_timer, NTB_HB_TIMEOUT);
+}
+
/* BWD doesn't have link status interrupt, poll on that platform */
static void bwd_link_poll(struct work_struct *work)
{
@@ -509,6 +600,16 @@ static void bwd_link_poll(struct work_struct *work)
if (rc)
dev_err(&ndev->pdev->dev,
"Error determining link status\n");
+
+ /* Check to see if a link error is the cause of the link down */
+ if (ndev->link_status == NTB_LINK_DOWN) {
+ u32 status32 = readl(ndev->reg_base +
+ BWD_LTSSMSTATEJMP_OFFSET);
+ if (status32 & BWD_LTSSMSTATEJMP_FORCEDETECT) {
+ schedule_delayed_work(&ndev->lr_timer, 0);
+ return;
+ }
+ }
}

schedule_delayed_work(&ndev->hb_timer, NTB_HB_TIMEOUT);
@@ -693,6 +794,7 @@ static int ntb_bwd_setup(struct ntb_device *ndev)

/* Since bwd doesn't have a link interrupt, setup a poll timer */
INIT_DELAYED_WORK(&ndev->hb_timer, bwd_link_poll);
+ INIT_DELAYED_WORK(&ndev->lr_timer, bwd_link_recovery);
schedule_delayed_work(&ndev->hb_timer, NTB_HB_TIMEOUT);

return 0;
@@ -733,8 +835,10 @@ static int ntb_device_setup(struct ntb_device *ndev)

static void ntb_device_free(struct ntb_device *ndev)
{
- if (ndev->hw_type == BWD_HW)
+ if (ndev->hw_type == BWD_HW) {
cancel_delayed_work_sync(&ndev->hb_timer);
+ cancel_delayed_work_sync(&ndev->lr_timer);
+ }
}

static irqreturn_t bwd_callback_msix_irq(int irq, void *data)
diff --git a/drivers/ntb/ntb_hw.h b/drivers/ntb/ntb_hw.h
index 72fcb22..3a15d49 100644
--- a/drivers/ntb/ntb_hw.h
+++ b/drivers/ntb/ntb_hw.h
@@ -125,10 +125,15 @@ struct ntb_device {
unsigned char num_msix;
unsigned char bits_per_vector;
unsigned char max_cbs;
+ unsigned char link_width;
+ unsigned char link_speed;
unsigned char link_status;
+
struct delayed_work hb_timer;
unsigned long last_ts;

+ struct delayed_work lr_timer;
+
struct dentry *debugfs_dir;
};

diff --git a/drivers/ntb/ntb_regs.h b/drivers/ntb/ntb_regs.h
index 4fe135a..8f3f903 100644
--- a/drivers/ntb/ntb_regs.h
+++ b/drivers/ntb/ntb_regs.h
@@ -114,6 +114,7 @@
#define BWD_MBAR45_OFFSET 0xb020
#define BWD_DEVCTRL_OFFSET 0xb048
#define BWD_LINK_STATUS_OFFSET 0xb052
+#define BWD_ERRCORSTS_OFFSET 0xb110

#define BWD_SBAR2XLAT_OFFSET 0x0008
#define BWD_SBAR4XLAT_OFFSET 0x0010
@@ -131,6 +132,20 @@
#define BWD_B2B_SPADSEMA_OFFSET 0x80c0
#define BWD_B2B_STKYSPAD_OFFSET 0x80c4

+#define BWD_MODPHY_PCSREG4 0x1c004
+#define BWD_MODPHY_PCSREG6 0x1c006
+
+#define BWD_IP_BASE 0xC000
+#define BWD_DESKEWSTS_OFFSET (BWD_IP_BASE + 0x3024)
+#define BWD_LTSSMERRSTS0_OFFSET (BWD_IP_BASE + 0x3180)
+#define BWD_LTSSMSTATEJMP_OFFSET (BWD_IP_BASE + 0x3040)
+#define BWD_IBSTERRRCRVSTS0_OFFSET (BWD_IP_BASE + 0x3324)
+
+#define BWD_DESKEWSTS_DBERR (1 << 15)
+#define BWD_LTSSMERRSTS0_UNEXPECTEDEI (1 << 20)
+#define BWD_LTSSMSTATEJMP_FORCEDETECT (1 << 2)
+#define BWD_IBIST_ERR_OFLOW 0x7FFF7FFF
+
#define NTB_CNTL_BAR23_SNOOP (1 << 2)
#define NTB_CNTL_BAR45_SNOOP (1 << 6)
#define BWD_CNTL_LINK_DOWN (1 << 16)
--
1.7.9.5