netdev - RE: [PATCH net 1/2] net: fec: Restart PPS after link state change

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Message-ID:
 <AM9PR04MB8505DB0E7FEEF2783DD6FB9E886F2@AM9PR04MB8505.eurprd04.prod.outlook.com>
Date: Mon, 23 Sep 2024 10:41:59 +0000
From: Wei Fang <wei.fang@....com>
To: Csókás, Bence <csokas.bence@...lan.hu>
CC: Shenwei Wang <shenwei.wang@....com>, Clark Wang <xiaoning.wang@....com>,
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo
 Abeni <pabeni@...hat.com>, Richard Cochran <richardcochran@...il.com>, "David
 S. Miller" <davem@...emloft.net>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, Frank Li <Frank.Li@...escale.com>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net 1/2] net: fec: Restart PPS after link state change

> -----Original Message-----
> From: Csókás, Bence <csokas.bence@...lan.hu>
> Sent: 2024年9月23日 17:24
> To: David S. Miller <davem@...emloft.net>; Frank Li
> <Frank.Li@...escale.com>; imx@...ts.linux.dev; netdev@...r.kernel.org;
> linux-kernel@...r.kernel.org
> Cc: Csókás, Bence <csokas.bence@...lan.hu>; Wei Fang <wei.fang@....com>;
> Shenwei Wang <shenwei.wang@....com>; Clark Wang
> <xiaoning.wang@....com>; Eric Dumazet <edumazet@...gle.com>; Jakub
> Kicinski <kuba@...nel.org>; Paolo Abeni <pabeni@...hat.com>; Richard
> Cochran <richardcochran@...il.com>
> Subject: [PATCH net 1/2] net: fec: Restart PPS after link state change
> 
> On link state change, the controller gets reset,
> causing PPS to drop out. Re-enable PPS if it was
> enabled before the controller reset.
> 
> Fixes: 6605b730c061 ("FEC: Add time stamping code and a PTP hardware
> clock")
> Signed-off-by: Csókás, Bence <csokas.bence@...lan.hu>
> ---
>  drivers/net/ethernet/freescale/fec.h      |  1 +
>  drivers/net/ethernet/freescale/fec_main.c |  7 ++++++-
>  drivers/net/ethernet/freescale/fec_ptp.c  | 12 ++++++++++++
>  3 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/freescale/fec.h
> b/drivers/net/ethernet/freescale/fec.h
> index a19cb2a786fd..afa0bfb974e6 100644
> --- a/drivers/net/ethernet/freescale/fec.h
> +++ b/drivers/net/ethernet/freescale/fec.h
> @@ -695,6 +695,7 @@ struct fec_enet_private {
>  };
> 
>  void fec_ptp_init(struct platform_device *pdev, int irq_idx);
> +void fec_ptp_restore_state(struct fec_enet_private *fep);
>  void fec_ptp_stop(struct platform_device *pdev);
>  void fec_ptp_start_cyclecounter(struct net_device *ndev);
>  int fec_ptp_set(struct net_device *ndev, struct kernel_hwtstamp_config
> *config,
> diff --git a/drivers/net/ethernet/freescale/fec_main.c
> b/drivers/net/ethernet/freescale/fec_main.c
> index acbb627d51bf..6c6dbda26f06 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -1244,8 +1244,10 @@ fec_restart(struct net_device *ndev)
>  	writel(ecntl, fep->hwp + FEC_ECNTRL);
>  	fec_enet_active_rxring(ndev);
> 
> -	if (fep->bufdesc_ex)
> +	if (fep->bufdesc_ex) {
>  		fec_ptp_start_cyclecounter(ndev);
> +		fec_ptp_restore_state(fep);
> +	}
> 
>  	/* Enable interrupts we wish to service */
>  	if (fep->link)
> @@ -1366,6 +1368,9 @@ fec_stop(struct net_device *ndev)
>  		val = readl(fep->hwp + FEC_ECNTRL);
>  		val |= FEC_ECR_EN1588;
>  		writel(val, fep->hwp + FEC_ECNTRL);
> +
> +		fec_ptp_start_cyclecounter(ndev);
> +		fec_ptp_restore_state(fep);
>  	}
>  }
> 
> diff --git a/drivers/net/ethernet/freescale/fec_ptp.c
> b/drivers/net/ethernet/freescale/fec_ptp.c
> index 4cffda363a14..54dc3d0503b2 100644
> --- a/drivers/net/ethernet/freescale/fec_ptp.c
> +++ b/drivers/net/ethernet/freescale/fec_ptp.c
> @@ -764,6 +764,18 @@ void fec_ptp_init(struct platform_device *pdev, int
> irq_idx)
>  	schedule_delayed_work(&fep->time_keep, HZ);
>  }
> 
> +/* Restore PTP functionality after a reset */
> +void fec_ptp_restore_state(struct fec_enet_private *fep)
> +{
> +	/* Restart PPS if needed */
> +	if (fep->pps_enable) {
> +		/* Reset turned it off, so adjust our status flag */
> +		fep->pps_enable = 0;

fep->pps_enable is protected by fep->tmreg_lock, see
fec_ptp_enable_pps(), I'm afraid doing this will lead to potential lock
evasion issue. So it is better to add lock protection to avoid warning
from the Coverity tool.

> +		/* Re-enable PPS */
> +		fec_ptp_enable_pps(fep, 1);
> +	}
> +}
> +
>  void fec_ptp_stop(struct platform_device *pdev)
>  {
>  	struct net_device *ndev = platform_get_drvdata(pdev);
> --
> 2.34.1
>