[PATCH net-next v2] bnxt_en: add unlocked version of bnxt_refclk_read

[PATCH net-next v2] bnxt_en: add unlocked version of bnxt_refclk_read

[Vadim Fedorenko]

Serialization of PHC read with FW reset mechanism uses ptp_lock which
also protects timecounter updates. This means we cannot grab it when
called from bnxt_cc_read(). Let's move locking into different function.

Fixes: 6c0828d00f07 ("bnxt_en: replace PTP spinlock with seqlock")
Signed-off-by: Vadim Fedorenko <vadfed@meta.com>
---
v1 -> v2:
* add lock around timecounter_init() in bnxt_ptp_timecounter_init()
---
 drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c | 35 +++++++++++++------
 1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
index f74afdab4f7d..91e7e08fabb1 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
@@ -73,19 +73,15 @@ static int bnxt_ptp_settime(struct ptp_clock_info *ptp_info,
 	return 0;
 }
 
-static int bnxt_refclk_read(struct bnxt *bp, struct ptp_system_timestamp *sts,
-			    u64 *ns)
+/* Caller holds ptp_lock */
+static int __bnxt_refclk_read(struct bnxt *bp, struct ptp_system_timestamp *sts,
+			      u64 *ns)
 {
 	struct bnxt_ptp_cfg *ptp = bp->ptp_cfg;
 	u32 high_before, high_now, low;
-	unsigned long flags;
 
-	/* We have to serialize reg access and FW reset */
-	read_seqlock_excl_irqsave(&ptp->ptp_lock, flags);
-	if (test_bit(BNXT_STATE_IN_FW_RESET, &bp->state)) {
-		read_sequnlock_excl_irqrestore(&ptp->ptp_lock, flags);
+	if (test_bit(BNXT_STATE_IN_FW_RESET, &bp->state))
 		return -EIO;
-	}
 
 	high_before = readl(bp->bar0 + ptp->refclk_mapped_regs[1]);
 	ptp_read_system_prets(sts);
@@ -97,12 +93,25 @@ static int bnxt_refclk_read(struct bnxt *bp, struct ptp_system_timestamp *sts,
 		low = readl(bp->bar0 + ptp->refclk_mapped_regs[0]);
 		ptp_read_system_postts(sts);
 	}
-	read_sequnlock_excl_irqrestore(&ptp->ptp_lock, flags);
 	*ns = ((u64)high_now << 32) | low;
 
 	return 0;
 }
 
+static int bnxt_refclk_read(struct bnxt *bp, struct ptp_system_timestamp *sts,
+			    u64 *ns)
+{
+	struct bnxt_ptp_cfg *ptp = bp->ptp_cfg;
+	unsigned long flags;
+	int rc;
+
+	/* We have to serialize reg access and FW reset */
+	read_seqlock_excl_irqsave(&ptp->ptp_lock, flags);
+	rc = __bnxt_refclk_read(bp, sts, ns);
+	read_sequnlock_excl_irqrestore(&ptp->ptp_lock, flags);
+	return rc;
+}
+
 static void bnxt_ptp_get_current_time(struct bnxt *bp)
 {
 	struct bnxt_ptp_cfg *ptp = bp->ptp_cfg;
@@ -674,7 +683,7 @@ static u64 bnxt_cc_read(const struct cyclecounter *cc)
 	struct bnxt_ptp_cfg *ptp = container_of(cc, struct bnxt_ptp_cfg, cc);
 	u64 ns = 0;
 
-	bnxt_refclk_read(ptp->bp, NULL, &ns);
+	__bnxt_refclk_read(ptp->bp, NULL, &ns);
 	return ns;
 }
 
@@ -936,6 +945,7 @@ static bool bnxt_pps_config_ok(struct bnxt *bp)
 static void bnxt_ptp_timecounter_init(struct bnxt *bp, bool init_tc)
 {
 	struct bnxt_ptp_cfg *ptp = bp->ptp_cfg;
+	unsigned long flags;
 
 	if (!ptp->ptp_clock) {
 		memset(&ptp->cc, 0, sizeof(ptp->cc));
@@ -952,8 +962,11 @@ static void bnxt_ptp_timecounter_init(struct bnxt *bp, bool init_tc)
 		}
 		ptp->next_overflow_check = jiffies + BNXT_PHC_OVERFLOW_PERIOD;
 	}
-	if (init_tc)
+	if (init_tc) {
+		write_seqlock_irqsave(&ptp->ptp_lock, flags);
 		timecounter_init(&ptp->tc, &ptp->cc, ktime_to_ns(ktime_get_real()));
+		write_sequnlock_irqrestore(&ptp->ptp_lock, flags);
+	}
 }
 
 /* Caller holds ptp_lock */
-- 
2.43.5

Re: [PATCH net-next v2] bnxt_en: add unlocked version of bnxt_refclk_read

[Pavan Chebbi]

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On Fri, Nov 8, 2024 at 3:19 AM Vadim Fedorenko <vadfed@meta.com> wrote:
>
> Serialization of PHC read with FW reset mechanism uses ptp_lock which
> also protects timecounter updates. This means we cannot grab it when
> called from bnxt_cc_read(). Let's move locking into different function.
>
> Fixes: 6c0828d00f07 ("bnxt_en: replace PTP spinlock with seqlock")
> Signed-off-by: Vadim Fedorenko <vadfed@meta.com>
> ---
> v1 -> v2:
> * add lock around timecounter_init() in bnxt_ptp_timecounter_init()
> ---
>  drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c | 35 +++++++++++++------
>  1 file changed, 24 insertions(+), 11 deletions(-)
>
Thanks Vadim.
Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>

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Re: [PATCH net-next v2] bnxt_en: add unlocked version of bnxt_refclk_read

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Thu, 7 Nov 2024 13:49:17 -0800 you wrote:
> Serialization of PHC read with FW reset mechanism uses ptp_lock which
> also protects timecounter updates. This means we cannot grab it when
> called from bnxt_cc_read(). Let's move locking into different function.
> 
> Fixes: 6c0828d00f07 ("bnxt_en: replace PTP spinlock with seqlock")
> Signed-off-by: Vadim Fedorenko <vadfed@meta.com>
> 
> [...]

Here is the summary with links:
  - [net-next,v2] bnxt_en: add unlocked version of bnxt_refclk_read
    https://git.kernel.org/netdev/net-next/c/f0fe51a04386

You are awesome, thank you!
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