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From:   Vladimir Oltean <vladimir.oltean@nxp.com>
To:     Colin Foster <colin.foster@in-advantage.com>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        Jakub Kicinski <kuba@kernel.org>,
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        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        Claudiu Manoil <claudiu.manoil@nxp.com>
Subject: Re: [PATCH v6 net-next 5/5] net: mscc: ocelot: use bulk reads for
 stats
Thread-Topic: [PATCH v6 net-next 5/5] net: mscc: ocelot: use bulk reads for
 stats
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Date:   Thu, 10 Feb 2022 10:36:37 +0000
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 <20220210041345.321216-6-colin.foster@in-advantage.com>
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On Wed, Feb 09, 2022 at 08:13:45PM -0800, Colin Foster wrote:
> Create and utilize bulk regmap reads instead of single access for gatheri=
ng
> stats. The background reading of statistics happens frequently, and over
> a few contiguous memory regions.
>=20
> High speed PCIe buses and MMIO access will probably see negligible
> performance increase. Lower speed buses like SPI and I2C could see
> significant performance increase, since the bus configuration and registe=
r
> access times account for a large percentage of data transfer time.
>=20
> Signed-off-by: Colin Foster <colin.foster@in-advantage.com>
> ---
>  drivers/net/ethernet/mscc/ocelot.c | 79 +++++++++++++++++++++++++-----
>  include/soc/mscc/ocelot.h          |  8 +++
>  2 files changed, 75 insertions(+), 12 deletions(-)
>=20
> diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/ms=
cc/ocelot.c
> index ab36732e7d3f..fdbd31149dfc 100644
> --- a/drivers/net/ethernet/mscc/ocelot.c
> +++ b/drivers/net/ethernet/mscc/ocelot.c
> @@ -1738,25 +1738,36 @@ void ocelot_get_strings(struct ocelot *ocelot, in=
t port, u32 sset, u8 *data)
>  EXPORT_SYMBOL(ocelot_get_strings);
> =20
>  /* Caller must hold &ocelot->stats_lock */
> -static void ocelot_update_stats_for_port(struct ocelot *ocelot, int port=
)
> +static int ocelot_update_stats_for_port(struct ocelot *ocelot, int port)
>  {
> -	int j;
> +	unsigned int idx =3D port * ocelot->num_stats;
> +	struct ocelot_stats_region *region;
> +	int err, j;
> =20
>  	/* Configure the port to read the stats from */
>  	ocelot_write(ocelot, SYS_STAT_CFG_STAT_VIEW(port), SYS_STAT_CFG);
> =20
> -	for (j =3D 0; j < ocelot->num_stats; j++) {
> -		u32 val;
> -		unsigned int idx =3D port * ocelot->num_stats + j;
> +	list_for_each_entry(region, &ocelot->stats_regions, node) {
> +		err =3D ocelot_bulk_read_rix(ocelot, SYS_COUNT_RX_OCTETS,
> +					   region->offset, region->buf,
> +					   region->count);
> +		if (err)
> +			return err;
> =20
> -		val =3D ocelot_read_rix(ocelot, SYS_COUNT_RX_OCTETS,
> -				      ocelot->stats_layout[j].offset);
> +		for (j =3D 0; j < region->count; j++) {
> +			u64 *stat =3D &ocelot->stats[idx + j];
> +			u64 val =3D region->buf[j];
> =20
> -		if (val < (ocelot->stats[idx] & U32_MAX))
> -			ocelot->stats[idx] +=3D (u64)1 << 32;
> +			if (val < (*stat & U32_MAX))
> +				*stat +=3D (u64)1 << 32;
> +
> +			*stat =3D (*stat & ~(u64)U32_MAX) + val;
> +		}
> =20
> -		ocelot->stats[idx] =3D (ocelot->stats[idx] & ~(u64)U32_MAX) + val;
> +		idx +=3D region->count;
>  	}
> +
> +	return err;
>  }
> =20
>  static void ocelot_check_stats_work(struct work_struct *work)
> @@ -1777,12 +1788,14 @@ static void ocelot_check_stats_work(struct work_s=
truct *work)
> =20
>  void ocelot_get_ethtool_stats(struct ocelot *ocelot, int port, u64 *data=
)
>  {
> -	int i;
> +	int i, err;
> =20
>  	mutex_lock(&ocelot->stats_lock);
> =20
>  	/* check and update now */
> -	ocelot_update_stats_for_port(ocelot, port);
> +	err =3D ocelot_update_stats_for_port(ocelot, port);

ocelot_check_stats_work() should also check for errors.

> +	if (err)
> +		dev_err(ocelot->dev, "Error %d updating ethtool stats\n", err);
> =20
>  	/* Copy all counters */
>  	for (i =3D 0; i < ocelot->num_stats; i++)
> @@ -1801,6 +1814,41 @@ int ocelot_get_sset_count(struct ocelot *ocelot, i=
nt port, int sset)
>  }
>  EXPORT_SYMBOL(ocelot_get_sset_count);
> =20
> +static int ocelot_prepare_stats_regions(struct ocelot *ocelot)
> +{
> +	struct ocelot_stats_region *region =3D NULL;
> +	unsigned int last;
> +	int i;
> +
> +	INIT_LIST_HEAD(&ocelot->stats_regions);
> +
> +	for (i =3D 0; i < ocelot->num_stats; i++) {
> +		if (region && ocelot->stats_layout[i].offset =3D=3D last + 1) {
> +			region->count++;
> +		} else {
> +			region =3D devm_kzalloc(ocelot->dev, sizeof(*region),
> +					      GFP_KERNEL);
> +			if (!region)
> +				return -ENOMEM;
> +
> +			region->offset =3D ocelot->stats_layout[i].offset;
> +			region->count =3D 1;
> +			list_add_tail(&region->node, &ocelot->stats_regions);
> +		}
> +
> +		last =3D ocelot->stats_layout[i].offset;
> +	}
> +
> +	list_for_each_entry(region, &ocelot->stats_regions, node) {
> +		region->buf =3D devm_kcalloc(ocelot->dev, region->count,
> +					   sizeof(*region->buf), GFP_KERNEL);
> +		if (!region->buf)
> +			return -ENOMEM;
> +	}
> +
> +	return 0;
> +}
> +
>  int ocelot_get_ts_info(struct ocelot *ocelot, int port,
>  		       struct ethtool_ts_info *info)
>  {
> @@ -2801,6 +2849,13 @@ int ocelot_init(struct ocelot *ocelot)
>  				 ANA_CPUQ_8021_CFG_CPUQ_BPDU_VAL(6),
>  				 ANA_CPUQ_8021_CFG, i);
> =20
> +	ret =3D ocelot_prepare_stats_regions(ocelot);
> +	if (ret) {
> +		destroy_workqueue(ocelot->stats_queue);
> +		destroy_workqueue(ocelot->owq);
> +		return ret;
> +	}
> +
>  	INIT_DELAYED_WORK(&ocelot->stats_work, ocelot_check_stats_work);
>  	queue_delayed_work(ocelot->stats_queue, &ocelot->stats_work,
>  			   OCELOT_STATS_CHECK_DELAY);
> diff --git a/include/soc/mscc/ocelot.h b/include/soc/mscc/ocelot.h
> index 312b72558659..d3291a5f7e88 100644
> --- a/include/soc/mscc/ocelot.h
> +++ b/include/soc/mscc/ocelot.h
> @@ -542,6 +542,13 @@ struct ocelot_stat_layout {
>  	char name[ETH_GSTRING_LEN];
>  };
> =20
> +struct ocelot_stats_region {
> +	struct list_head node;
> +	u32 offset;
> +	int count;
> +	u32 *buf;
> +};
> +
>  enum ocelot_tag_prefix {
>  	OCELOT_TAG_PREFIX_DISABLED	=3D 0,
>  	OCELOT_TAG_PREFIX_NONE,
> @@ -673,6 +680,7 @@ struct ocelot {
>  	struct regmap_field		*regfields[REGFIELD_MAX];
>  	const u32 *const		*map;
>  	const struct ocelot_stat_layout	*stats_layout;
> +	struct list_head		stats_regions;
>  	unsigned int			num_stats;
> =20
>  	u32				pool_size[OCELOT_SB_NUM][OCELOT_SB_POOL_NUM];
> --=20
> 2.25.1
>=