[PATCH 09/10] NTB: epf: Fix doorbell bitmask handling in db_read/db_clear

[Koichiro Den]

The EPF driver currently stores the incoming doorbell as a vector number
(irq_no + 1) in db_val and db_clear() clears all bits unconditionally.
This breaks db_read()/db_clear() semantics when multiple doorbells are
used.

Store doorbells as a bitmask (BIT_ULL(vector)) and make
db_clear(db_bits) clear only the specified bits. Use atomic64 operations
as db_val is updated from interrupt context.

Fixes: 812ce2f8d14e ("NTB: Add support for EPF PCI Non-Transparent Bridge")
Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
---
 drivers/ntb/hw/epf/ntb_hw_epf.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/ntb/hw/epf/ntb_hw_epf.c b/drivers/ntb/hw/epf/ntb_hw_epf.c
index 00956ab2fbf5..0018adc35f16 100644
--- a/drivers/ntb/hw/epf/ntb_hw_epf.c
+++ b/drivers/ntb/hw/epf/ntb_hw_epf.c
@@ -6,6 +6,7 @@
  * Author: Kishon Vijay Abraham I <kishon@xxxxxx>
  */
 
+#include <linux/atomic.h>
 #include <linux/delay.h>
 #include <linux/module.h>
 #include <linux/pci.h>
@@ -102,7 +103,7 @@ struct ntb_epf_dev {
 	unsigned int self_spad;
 	unsigned int peer_spad;
 
-	int db_val;
+	atomic64_t db_val;
 	u64 db_valid_mask;
 };
 
@@ -331,15 +332,16 @@ static irqreturn_t ntb_epf_vec_isr(int irq, void *dev)
 	int irq_no;
 
 	irq_no = irq - pci_irq_vector(ndev->ntb.pdev, 0);
-	ndev->db_val = irq_no + 1;
 
 	if (irq_no == 0) {
 		ntb_link_event(&ndev->ntb);
 	} else if (irq_no == 1) {
 		dev_warn_ratelimited(ndev->dev,
 				     "Unexpected irq_no 1 received. Treat it as DB#0.\n");
+		atomic64_or(BIT_ULL(0), &ndev->db_val);
 		ntb_db_event(&ndev->ntb, 0);
 	} else {
+		atomic64_or(BIT_ULL(irq_no - 2), &ndev->db_val);
 		ntb_db_event(&ndev->ntb, irq_no - 2);
 	}
 
@@ -524,7 +526,7 @@ static u64 ntb_epf_db_read(struct ntb_dev *ntb)
 {
 	struct ntb_epf_dev *ndev = ntb_ndev(ntb);
 
-	return ndev->db_val;
+	return atomic64_read(&ndev->db_val);
 }
 
 static int ntb_epf_db_clear_mask(struct ntb_dev *ntb, u64 db_bits)
@@ -536,7 +538,7 @@ static int ntb_epf_db_clear(struct ntb_dev *ntb, u64 db_bits)
 {
 	struct ntb_epf_dev *ndev = ntb_ndev(ntb);
 
-	ndev->db_val = 0;
+	atomic64_and(~db_bits, &ndev->db_val);
 
 	return 0;
 }
-- 
2.51.0