netdev - Re: [PATCH net] net: ti: iccsg-prueth: Fix 1 PPS sync

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Message-ID: <3fe8183a-08d3-47d3-b1a1-0d84f7bf58b7@linux.dev>
Date: Wed, 23 Oct 2024 11:22:36 +0100
From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
To: Meghana Malladi <m-malladi@...com>, vigneshr@...com, horms@...nel.org,
 jan.kiszka@...mens.com, diogo.ivo@...mens.com, pabeni@...hat.com,
 kuba@...nel.org, edumazet@...gle.com, davem@...emloft.net,
 andrew+netdev@...n.ch
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, srk@...com,
 Roger Quadros <rogerq@...nel.org>, danishanwar@...com
Subject: Re: [PATCH net] net: ti: iccsg-prueth: Fix 1 PPS sync

On 23/10/2024 10:12, Meghana Malladi wrote:
> The first PPS latch time needs to be calculated by the driver
> (in rounded off seconds) and configured as the start time
> offset for the cycle. After synchronizing two PTP clocks
> running as master/slave, missing this would cause master
> and slave to start immediately with some milliseconds
> drift which causes the PPS signal to never synchronize with
> the PTP master.
> 
> Fixes: 186734c15886 ("net: ti: icssg-prueth: add packet timestamping and ptp support")
> Signed-off-by: Meghana Malladi <m-malladi@...com>
> ---
>   drivers/net/ethernet/ti/icssg/icssg_prueth.c | 12 ++++++++++--
>   drivers/net/ethernet/ti/icssg/icssg_prueth.h | 11 +++++++++++
>   2 files changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/ti/icssg/icssg_prueth.c b/drivers/net/ethernet/ti/icssg/icssg_prueth.c
> index 0556910938fa..6b2cd7c898d0 100644
> --- a/drivers/net/ethernet/ti/icssg/icssg_prueth.c
> +++ b/drivers/net/ethernet/ti/icssg/icssg_prueth.c
> @@ -411,6 +411,8 @@ static int prueth_perout_enable(void *clockops_data,
>   	struct prueth_emac *emac = clockops_data;
>   	u32 reduction_factor = 0, offset = 0;
>   	struct timespec64 ts;
> +	u64 current_cycle;
> +	u64 start_offset;
>   	u64 ns_period;
>   
>   	if (!on)
> @@ -449,8 +451,14 @@ static int prueth_perout_enable(void *clockops_data,
>   	writel(reduction_factor, emac->prueth->shram.va +
>   		TIMESYNC_FW_WC_SYNCOUT_REDUCTION_FACTOR_OFFSET);
>   
> -	writel(0, emac->prueth->shram.va +
> -		TIMESYNC_FW_WC_SYNCOUT_START_TIME_CYCLECOUNT_OFFSET);
> +	current_cycle = icssg_readq(emac->prueth->shram.va +
> +				    TIMESYNC_FW_WC_CYCLECOUNT_OFFSET);
> +
> +	/* Rounding of current_cycle count to next second */
> +	start_offset = ((current_cycle / MSEC_PER_SEC) + 1) * MSEC_PER_SEC;

This looks more like roundup(current_cycle, MSEC_PER_SEC), let's use it
instead of open coding.

> +
> +	icssg_writeq(start_offset, emac->prueth->shram.va +
> +		     TIMESYNC_FW_WC_SYNCOUT_START_TIME_CYCLECOUNT_OFFSET);
>   
>   	return 0;
>   }
> diff --git a/drivers/net/ethernet/ti/icssg/icssg_prueth.h b/drivers/net/ethernet/ti/icssg/icssg_prueth.h
> index 8722bb4a268a..a4af2dbcca31 100644
> --- a/drivers/net/ethernet/ti/icssg/icssg_prueth.h
> +++ b/drivers/net/ethernet/ti/icssg/icssg_prueth.h
> @@ -330,6 +330,17 @@ static inline int prueth_emac_slice(struct prueth_emac *emac)
>   extern const struct ethtool_ops icssg_ethtool_ops;
>   extern const struct dev_pm_ops prueth_dev_pm_ops;
>   
> +static inline u64 icssg_readq(const void __iomem *addr)
> +{
> +	return readl(addr) + ((u64)readl(addr + 4) << 32);
> +}
> +
> +static inline void icssg_writeq(u64 val, void __iomem *addr)
> +{
> +	writel(lower_32_bits(val), addr);
> +	writel(upper_32_bits(val), addr + 4);
> +}
> +
>   /* Classifier helpers */
>   void icssg_class_set_mac_addr(struct regmap *miig_rt, int slice, u8 *mac);
>   void icssg_class_set_host_mac_addr(struct regmap *miig_rt, const u8 *mac);
> 
> base-commit: 73840ca5ef361f143b89edd5368a1aa8c2979241