Commit c529aa30 authored by Jon Mason's avatar Jon Mason
Browse files

NTB: Xeon Doorbell errata workaround 



Modifications to the 14th bit of the B2BDOORBELL register will not be
mirrored to the remote system due to a hardware issue.  To get around
the issue, shrink the number of available doorbell bits by 1.  The max
number of doorbells was being used as a way to referencing the Link
Doorbell bit.  Since this would no longer work, the driver must now
explicitly reference that bit.

This does not affect the xeon_errata_workaround case, as it is not using
the b2bdoorbell register.

Signed-off-by: default avatarJon Mason <jon.mason@intel.com>
parent 5e01dc7b

drivers/ntb/ntb_hw.c

+15 −5
Original line number Diff line number Diff line
@@ -678,6 +678,7 @@ static int ntb_xeon_setup(struct ntb_device *ndev) 
				return -EINVAL;



			ndev->limits.max_mw = SNB_ERRATA_MAX_MW;

			ndev->limits.max_db_bits = SNB_MAX_DB_BITS;

			ndev->reg_ofs.spad_write = ndev->mw[1].vbase +

						   SNB_SPAD_OFFSET;

			ndev->reg_ofs.rdb = ndev->mw[1].vbase +
@@ -690,6 +691,13 @@ static int ntb_xeon_setup(struct ntb_device *ndev) 
			       SNB_PBAR4LMT_OFFSET);

		} else {

			ndev->limits.max_mw = SNB_MAX_MW;



			/* HW Errata on bit 14 of b2bdoorbell register.  Writes

			 * will not be mirrored to the remote system.  Shrink

			 * the number of bits by one, since bit 14 is the last

			 * bit.

			 */

			ndev->limits.max_db_bits = SNB_MAX_DB_BITS - 1;

			ndev->reg_ofs.spad_write = ndev->reg_base +

						   SNB_B2B_SPAD_OFFSET;

			ndev->reg_ofs.rdb = ndev->reg_base +
@@ -769,6 +777,7 @@ static int ntb_xeon_setup(struct ntb_device *ndev) 
		 * have an equal amount.

		 */

		ndev->limits.max_spads = SNB_MAX_COMPAT_SPADS / 2;

		ndev->limits.max_db_bits = SNB_MAX_DB_BITS;

		/* Note: The SDOORBELL is the cause of the errata.  You REALLY

		 * don't want to touch it.

		 */
@@ -793,6 +802,7 @@ static int ntb_xeon_setup(struct ntb_device *ndev) 
		 * have an equal amount.

		 */

		ndev->limits.max_spads = SNB_MAX_COMPAT_SPADS / 2;

		ndev->limits.max_db_bits = SNB_MAX_DB_BITS;

		ndev->reg_ofs.rdb = ndev->reg_base + SNB_PDOORBELL_OFFSET;

		ndev->reg_ofs.ldb = ndev->reg_base + SNB_SDOORBELL_OFFSET;

		ndev->reg_ofs.ldb_mask = ndev->reg_base + SNB_SDBMSK_OFFSET;
@@ -819,7 +829,6 @@ static int ntb_xeon_setup(struct ntb_device *ndev) 
	ndev->reg_ofs.lnk_stat = ndev->reg_base + SNB_SLINK_STATUS_OFFSET;

	ndev->reg_ofs.spci_cmd = ndev->reg_base + SNB_PCICMD_OFFSET;



	ndev->limits.max_db_bits = SNB_MAX_DB_BITS;

	ndev->limits.msix_cnt = SNB_MSIX_CNT;

	ndev->bits_per_vector = SNB_DB_BITS_PER_VEC;
@@ -986,7 +995,7 @@ static irqreturn_t xeon_event_msix_irq(int irq, void *dev) 
		dev_err(&ndev->pdev->dev, "Error determining link status\n");



	/* bit 15 is always the link bit */

	writew(1 << ndev->limits.max_db_bits, ndev->reg_ofs.ldb);

	writew(1 << SNB_LINK_DB, ndev->reg_ofs.ldb);



	return IRQ_HANDLED;

}
@@ -1176,9 +1185,10 @@ static int ntb_setup_interrupts(struct ntb_device *ndev) 
	 */

	if (ndev->hw_type == BWD_HW)

		writeq(~0, ndev->reg_ofs.ldb_mask);

	else

		writew(~(1 << ndev->limits.max_db_bits),

		       ndev->reg_ofs.ldb_mask);

	else {

		u16 var = 1 << SNB_LINK_DB;

		writew(~var, ndev->reg_ofs.ldb_mask);

	}



	rc = ntb_setup_msix(ndev);

	if (!rc)

drivers/ntb/ntb_regs.h

+1 −0
Original line number Diff line number Diff line
@@ -55,6 +55,7 @@ 
#define SNB_MAX_COMPAT_SPADS	16

/* Reserve the uppermost bit for link interrupt */

#define SNB_MAX_DB_BITS		15

#define SNB_LINK_DB		15

#define SNB_DB_BITS_PER_VEC	5

#define SNB_MAX_MW		2

#define SNB_ERRATA_MAX_MW	1

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