bnxt_en: cache only 24 bits of hw counter

This hardware can provide only 48 bits of cycle counter. We can leave
only 24 bits in the cache to extend RX timestamps from 32 bits to 48
bits. Lower 8 bits of the cached value will be used to check for
roll-over while extending to full 48 bits.
This change makes cache writes atomic even on 32 bit platforms and we
can simply use READ_ONCE()/WRITE_ONCE() pair and remove spinlock. The
configuration structure will be also reduced by 4 bytes.

Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Vadim Fedorenko <vadfed@meta.com>
Link: https://patch.msgid.link/20241103215108.557531-1-vadfed@meta.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
index fa514be87650286b181aa1c2a0acaca216333d4f..ccf0ab304ed948d1e851bd839ddd1745ebb7c64e 100644 (file)
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
@@ -106,7 +106,7 @@ static void bnxt_ptp_get_current_time(struct bnxt *bp)
        if (!ptp)
                return;
        spin_lock_irqsave(&ptp->ptp_lock, flags);
-       WRITE_ONCE(ptp->old_time, ptp->current_time);
+       WRITE_ONCE(ptp->old_time, ptp->current_time >> BNXT_HI_TIMER_SHIFT);
        bnxt_refclk_read(bp, NULL, &ptp->current_time);
        spin_unlock_irqrestore(&ptp->ptp_lock, flags);
 }
@@ -174,7 +174,7 @@ void bnxt_ptp_update_current_time(struct bnxt *bp)
        struct bnxt_ptp_cfg *ptp = bp->ptp_cfg;
 
        bnxt_refclk_read(ptp->bp, NULL, &ptp->current_time);
-       WRITE_ONCE(ptp->old_time, ptp->current_time);
+       WRITE_ONCE(ptp->old_time, ptp->current_time >> BNXT_HI_TIMER_SHIFT);
 }
 
 static int bnxt_ptp_adjphc(struct bnxt_ptp_cfg *ptp, s64 delta)
@@ -813,7 +813,7 @@ int bnxt_get_rx_ts_p5(struct bnxt *bp, u64 *ts, u32 pkt_ts)
        if (!ptp)
                return -ENODEV;
 
-       BNXT_READ_TIME64(ptp, time, ptp->old_time);
+       time = (u64)READ_ONCE(ptp->old_time) << BNXT_HI_TIMER_SHIFT;
        *ts = (time & BNXT_HI_TIMER_MASK) | pkt_ts;
        if (pkt_ts < (time & BNXT_LO_TIMER_MASK))
                *ts += BNXT_LO_TIMER_MASK + 1;
@@ -1079,7 +1079,7 @@ int bnxt_ptp_init(struct bnxt *bp, bool phc_cfg)
 
                spin_lock_irqsave(&ptp->ptp_lock, flags);
                bnxt_refclk_read(bp, NULL, &ptp->current_time);
-               WRITE_ONCE(ptp->old_time, ptp->current_time);
+               WRITE_ONCE(ptp->old_time, ptp->current_time >> BNXT_HI_TIMER_SHIFT);
                spin_unlock_irqrestore(&ptp->ptp_lock, flags);
                ptp_schedule_worker(ptp->ptp_clock, 0);
        }

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.h b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.h
index f322466ecad350da1bf213007370e29a261a2a0c..3ac5cbc1c5c42c093de66eac22e2f956389ebecd 100644 (file)
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.h
@@ -21,6 +21,7 @@
 #define BNXT_DEVCLK_FREQ       1000000
 #define BNXT_LO_TIMER_MASK     0x0000ffffffffUL
 #define BNXT_HI_TIMER_MASK     0xffff00000000UL
+#define BNXT_HI_TIMER_SHIFT    24
 
 #define BNXT_PTP_DFLT_TX_TMO   1000 /* ms */
 #define BNXT_PTP_QTS_TIMEOUT   1000
@@ -106,10 +107,11 @@ struct bnxt_ptp_cfg {
        /* serialize ts tx request queuing */
        spinlock_t              ptp_tx_lock;
        u64                     current_time;
-       u64                     old_time;
        unsigned long           next_period;
        unsigned long           next_overflow_check;
        u32                     cmult;
+       /* cache of upper 24 bits of cyclecoutner. 8 bits are used to check for roll-over */
+       u32                     old_time;
        /* a 23b shift cyclecounter will overflow in ~36 mins.  Check overflow every 18 mins. */
        #define BNXT_PHC_OVERFLOW_PERIOD        (18 * 60 * HZ)
 
@@ -145,20 +147,6 @@ struct bnxt_ptp_cfg {
        struct bnxt_ptp_stats   stats;
 };
 
-#if BITS_PER_LONG == 32
-#define BNXT_READ_TIME64(ptp, dst, src)                                \
-do {                                                           \
-       unsigned long flags;                                    \
-                                                               \
-       spin_lock_irqsave(&(ptp)->ptp_lock, flags);             \
-       (dst) = (src);                                          \
-       spin_unlock_irqrestore(&(ptp)->ptp_lock, flags);        \
-} while (0)
-#else
-#define BNXT_READ_TIME64(ptp, dst, src)                \
-       ((dst) = READ_ONCE(src))
-#endif
-
 #define BNXT_PTP_INC_TX_AVAIL(ptp)             \
 do {                                           \
        spin_lock_bh(&(ptp)->ptp_tx_lock);      \