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arch/arm/stm32: deliver direct hardware counter timestamps for PTP.

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The MAC hardware counter is the PTP clock reference. Delivering its
raw timestamp directly (instead of synthesizing one against
CLOCK_REALTIME, which starts at an arbitrary boot-time phase) lets the
PTP daemon close the feedback loop and phase-lock the MAC counter -
and therefore the physical PPS output - to the master.

Assisted-by: Gemini:gemini-3.8-flash-medium
Signed-off-by: Daniel P. Carvalho <danieloak@gmail.com>
This commit is contained in:
Daniel P. Carvalho 2026-09-17 14:37:27 -03:00 • committed by Alan C. Assis
parent 6f7d54d096
commit c21d96eb68
1 changed files with 11 additions and 29 deletions
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40
arch/arm/src/common/stm32/stm32_eth_m3m4_v1.c
View file

@ -774,8 +774,10 @@ static int stm32_ethconfig(struct stm32_ethmac_s *priv);
#ifdef CONFIG_STM32_ETH_PTP
static int stm32_eth_ptp_adjust(long ppb);
static void stm32_eth_ptp_init(uint64_t timestamp);
#ifdef CONFIG_STM32_ETH_PTP_RTC_HIRES
static uint64_t stm32_eth_ptp_gettime(void);
#endif
#endif
#ifdef CONFIG_STM32_ETH_TIMESTAMP_RX
static void stm32_eth_ptp_convert_rxtime(struct stm32_ethmac_s *priv);
@ -3707,6 +3709,7 @@ static void stm32_eth_ptp_init(uint64_t timestamp)
#endif
}
#ifdef CONFIG_STM32_ETH_PTP_RTC_HIRES
/****************************************************************************
* Name: stm32_eth_ptp_gettime
*
@ -3751,6 +3754,7 @@ static uint64_t stm32_eth_ptp_gettime(void)
return ((uint64_t)high2 << 32);
}
}
#endif
static inline void ptp_to_timespec(uint64_t timestamp, struct timespec *ts)
{
@ -3763,7 +3767,6 @@ static inline void ptp_to_timespec(uint64_t timestamp, struct timespec *ts)
static void stm32_eth_ptp_convert_rxtime(struct stm32_ethmac_s *priv)
{
uint64_t timestamp;
struct timespec rxtime;
timestamp = ((uint64_t)priv->rxtimehigh << 32)
| ((priv->rxtimelow & ETH_PTPTSLR_MASK) << 1);
@ -3782,35 +3785,14 @@ static void stm32_eth_ptp_convert_rxtime(struct stm32_ethmac_s *priv)
return;
}
#ifdef CONFIG_STM32_ETH_PTP_RTC_HIRES
/* PTP is the system time reference, just add the base time */
/* Convert 64-bit hardware timestamp directly into timespec.
* In a PTP system, the MAC hardware counter is the PTP clock reference.
* Delivering the hardware counter's timestamp directly allows the PTP
* daemon to close the feedback loop and phase-lock the MAC counter (and
* therefore the physical PPS output) to the master.
*/
ptp_to_timespec(timestamp, &rxtime);
clock_timespec_add(&rxtime, &g_stm32_eth_ptp_basetime,
&priv->dev.d_rxtime);
#else
{
struct timespec realtime;
uint64_t ptptime;
irqstate_t flags;
/* Sample PTP and CLOCK_REALTIME close to each other */
clock_gettime(CLOCK_REALTIME, &realtime);
flags = spin_lock_irqsave(&g_rtc_lock);
ptptime = stm32_eth_ptp_gettime();
spin_unlock_irqrestore(&g_rtc_lock, flags);
/* Compute how much time has elapsed since packet reception
* and add that to current time.
*/
timestamp = ptptime - timestamp;
ptp_to_timespec(timestamp, &rxtime);
clock_timespec_add(&rxtime, &realtime, &priv->dev.d_rxtime);
}
#endif /* CONFIG_STM32_ETH_PTP_RTC_HIRES */
ptp_to_timespec(timestamp, &priv->dev.d_rxtime);
}
#endif /* CONFIG_STM32_ETH_TIMESTAMP_RX */