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Commit 113bf1c9 authored by Jon Mason's avatar Jon Mason
Browse files

NTB: BWD Link Recovery 



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: default avatarJon Mason <jon.mason@intel.com>
parent 948d3a65

drivers/ntb/ntb_hw.c

+107 −3
Original line number Diff line number Diff line
@@ -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 { 


static 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);
@@ -703,6 +804,7 @@ 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;
@@ -743,8 +845,10 @@ 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)

drivers/ntb/ntb_hw.h

+5 −0
Original line number Diff line number Diff line
@@ -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;

};

drivers/ntb/ntb_regs.h

+15 −0
Original line number Diff line number Diff line
@@ -115,6 +115,7 @@ 
#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
@@ -132,6 +133,20 @@ 
#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)