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Date: Mon, 6 Mar 2023 16:06:51 +0200
From: Vladimir Oltean <olteanv@...il.com>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: "David S. Miller" <davem@...emloft.net>,
Andrew Lunn <andrew@...n.ch>,
Eric Dumazet <edumazet@...gle.com>,
Florian Fainelli <f.fainelli@...il.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Woojung Huh <woojung.huh@...rochip.com>, kernel@...gutronix.de,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
UNGLinuxDriver@...rochip.com
Subject: Re: [PATCH net-next v1 2/2] net: dsa: microchip: add ETS Qdisc
support for KSZ9477 series
Hi Oleksij,
On Mon, Mar 06, 2023 at 01:49:40PM +0100, Oleksij Rempel wrote:
> Add ETS Qdisc support for KSZ9477 of switches. Current implementation is
> limited to strict priority mode.
>
> Tested on KSZ8563R with following configuration:
> tc qdisc replace dev lan2 root handle 1: ets strict 4 \
> priomap 3 3 2 2 1 1 0 0
> ip link add link lan2 name v1 type vlan id 1 \
> egress-qos-map 0:0 1:1 2:2 3:3 4:4 5:5 6:6 7:7
>
> and patched iperf3 version:
> https://github.com/esnet/iperf/pull/1476
> iperf3 -c 172.17.0.1 -b100M -l1472 -t100 -u -R --sock-prio 2
>
> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> ---
> drivers/net/dsa/microchip/ksz_common.c | 178 +++++++++++++++++++++++++
> drivers/net/dsa/microchip/ksz_common.h | 12 ++
> 2 files changed, 190 insertions(+)
>
> diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
> index ae05fe0b0a81..f32ad39c1d8d 100644
> --- a/drivers/net/dsa/microchip/ksz_common.c
> +++ b/drivers/net/dsa/microchip/ksz_common.c
> @@ -3172,12 +3172,190 @@ static int ksz_setup_tc_cbs(struct dsa_switch *ds, int port,
> MTI_SHAPING_SRP);
> }
>
> +static int ksz_ets_band_to_queue(struct tc_ets_qopt_offload_replace_params *p,
> + int band)
> +{
> + /* Compared to queues, bands prioritize packets differently. In strict
> + * priority mode, the lowest priority is assigned to Queue 0 while the
> + * highest priority is given to Band 0.
> + */
> + return p->bands - 1 - band;
> +}
> +
> +static int ksz_queue_set_strict(struct ksz_device *dev, int port, int queue)
> +{
> + int ret;
> +
> + /* In order to ensure proper prioritization, it is necessary to set the
> + * rate limit for the related queue to zero. Otherwise strict priority
> + * mode will not work.
> + */
> + ret = ksz_pwrite8(dev, port, KSZ9477_REG_PORT_OUT_RATE_0 + queue,
> + KSZ9477_OUT_RATE_NO_LIMIT);
> + if (ret)
> + return ret;
> +
> + ret = ksz_pwrite32(dev, port, REG_PORT_MTI_QUEUE_INDEX__4, queue);
> + if (ret)
> + return ret;
> +
> + return ksz_setup_tc_mode(dev, port, MTI_SCHEDULE_STRICT_PRIO,
> + MTI_SHAPING_OFF);
> +}
> +
> +static int ksz_queue_set_wrr(struct ksz_device *dev, int port, int queue,
> + int weight)
> +{
> + int ret;
> +
> + /* In order to ensure proper prioritization, it is necessary to set the
> + * rate limit for the related queue to zero. Otherwise weighted round
> + * robin mode will not work.
> + */
> + ret = ksz_pwrite8(dev, port, KSZ9477_REG_PORT_OUT_RATE_0 + queue,
> + KSZ9477_OUT_RATE_NO_LIMIT);
> + if (ret)
> + return ret;
> +
> + ret = ksz_pwrite32(dev, port, REG_PORT_MTI_QUEUE_INDEX__4, queue);
> + if (ret)
> + return ret;
> +
> + ret = ksz_setup_tc_mode(dev, port, MTI_SCHEDULE_WRR,
> + MTI_SHAPING_OFF);
> + if (ret)
> + return ret;
> +
> + return ksz_pwrite8(dev, port, KSZ9477_PORT_MTI_QUEUE_CTRL_1, weight);
> +}
> +
> +static int ksz_tc_ets_add(struct ksz_device *dev, int port,
> + struct tc_ets_qopt_offload_replace_params *p)
> +{
> + int ret, band, tc_prio;
> + u32 queue_map = 0;
> +
> + /* Configure queue scheduling mode for all bands. Currently only strict
> + * prio mode is supported.
> + */
> + for (band = 0; band < p->bands; band++) {
> + int queue = ksz_ets_band_to_queue(p, band);
> +
> + ret = ksz_queue_set_strict(dev, port, queue);
> + if (ret)
> + return ret;
> + }
> +
> + /* Configure the mapping between traffic classes and queues. Note:
> + * priomap variable support 16 traffic classes, but the chip can handle
> + * only 8 classes.
> + */
> + for (tc_prio = 0; tc_prio < ARRAY_SIZE(p->priomap); tc_prio++) {
> + int queue;
> +
> + if (tc_prio > KSZ9477_MAX_TC_PRIO)
> + break;
> +
> + queue = ksz_ets_band_to_queue(p, p->priomap[tc_prio]);
> + queue_map |= queue << (tc_prio * KSZ9477_PORT_TC_MAP_S);
> + }
> +
> + return ksz_pwrite32(dev, port, KSZ9477_PORT_MRI_TC_MAP__4, queue_map);
> +}
> +
> +static int ksz_tc_ets_del(struct ksz_device *dev, int port)
> +{
> + int ret, queue;
> +
> + /* To restore the default chip configuration, set all queues to use the
> + * WRR scheduler with a weight of 1.
> + */
> + for (queue = 0; queue < dev->info->num_tx_queues; queue++) {
> + ret = ksz_queue_set_wrr(dev, port, queue,
> + KSZ9477_DEFAULT_WRR_WEIGHT);
> + if (ret)
> + return ret;
> + }
> +
> + /* Revert the queue mapping for TC-priority to its default setting on
> + * the chip.
> + */
> + return ksz_pwrite32(dev, port, KSZ9477_PORT_MRI_TC_MAP__4,
> + KSZ9477_DEFAULT_TC_MAP);
> +}
> +
> +static int ksz_tc_ets_validate(struct ksz_device *dev, int port,
> + struct tc_ets_qopt_offload_replace_params *p)
> +{
> + int band;
> +
> + /* Since it is not feasible to share one port among multiple qdisc,
> + * the user must configure all available queues appropriately.
> + */
> + if (p->bands != dev->info->num_tx_queues) {
> + dev_err(dev->dev, "Not supported amount of bands. It should be %d\n",
> + dev->info->num_tx_queues);
> + return -EOPNOTSUPP;
> + }
> +
> + for (band = 0; band < p->bands; ++band) {
> + /* The KSZ switches utilize a weighted round robin configuration
> + * where a certain number of packets can be transmitted from a
> + * queue before the next queue is serviced. For more information
> + * on this, refer to section 5.2.8.4 of the KSZ8565R
> + * documentation on the Port Transmit Queue Control 1 Register.
> + * However, the current ETS Qdisc implementation (as of February
> + * 2023) assigns a weight to each queue based on the number of
> + * bytes or extrapolated bandwidth in percentages. Since this
> + * differs from the KSZ switches' method and we don't want to
> + * fake support by converting bytes to packets, we have decided
> + * to return an error instead.
> + */
> + if (p->quanta[band]) {
> + dev_err(dev->dev, "Quanta/weights configuration is not supported.\n");
> + return -EOPNOTSUPP;
> + }
So what does the user gain using tc-ets over tc-mqprio? That has a way
to set up strict prioritization and prio:tc maps as well, and to my
knowledge mqprio is vastly more popular in non-DCB setups than tc-ets.
The only thing is that with mqprio, AFAIK, the round robin between TXQs
belonging to the same traffic class is not weighted.
> + }
> +
> + return 0;
> +}
> +
> +static int ksz_tc_setup_qdisc_ets(struct dsa_switch *ds, int port,
> + struct tc_ets_qopt_offload *qopt)
> +{
> + struct ksz_device *dev = ds->priv;
> + int ret;
> +
> + if (qopt->parent != TC_H_ROOT) {
> + dev_err(dev->dev, "Parent should be \"root\"\n");
> + return -EOPNOTSUPP;
> + }
> +
> + switch (qopt->command) {
> + case TC_ETS_REPLACE:
> + ret = ksz_tc_ets_validate(dev, port, &qopt->replace_params);
> + if (ret)
> + return ret;
> +
> + return ksz_tc_ets_add(dev, port, &qopt->replace_params);
> + case TC_ETS_DESTROY:
> + return ksz_tc_ets_del(dev, port);
> + case TC_ETS_STATS:
> + case TC_ETS_GRAFT:
> + return -EOPNOTSUPP;
> + }
> +
> + return -EOPNOTSUPP;
> +}
> +
> static int ksz_setup_tc(struct dsa_switch *ds, int port,
> enum tc_setup_type type, void *type_data)
> {
> switch (type) {
> case TC_SETUP_QDISC_CBS:
> return ksz_setup_tc_cbs(ds, port, type_data);
> + case TC_SETUP_QDISC_ETS:
> + return ksz_tc_setup_qdisc_ets(ds, port, type_data);
> default:
> return -EOPNOTSUPP;
> }
> diff --git a/drivers/net/dsa/microchip/ksz_common.h b/drivers/net/dsa/microchip/ksz_common.h
> index f53834bbe896..7618a4714e06 100644
> --- a/drivers/net/dsa/microchip/ksz_common.h
> +++ b/drivers/net/dsa/microchip/ksz_common.h
> @@ -657,6 +657,15 @@ static inline int is_lan937x(struct ksz_device *dev)
> #define KSZ8_LEGAL_PACKET_SIZE 1518
> #define KSZ9477_MAX_FRAME_SIZE 9000
>
> +#define KSZ9477_REG_PORT_OUT_RATE_0 0x0420
> +#define KSZ9477_OUT_RATE_NO_LIMIT 0
> +
> +#define KSZ9477_PORT_MRI_TC_MAP__4 0x0808
> +#define KSZ9477_DEFAULT_TC_MAP 0x33221100
> +
> +#define KSZ9477_PORT_TC_MAP_S 4
> +#define KSZ9477_MAX_TC_PRIO 7
> +
> /* CBS related registers */
> #define REG_PORT_MTI_QUEUE_INDEX__4 0x0900
>
> @@ -670,6 +679,9 @@ static inline int is_lan937x(struct ksz_device *dev)
> #define MTI_SHAPING_SRP 1
> #define MTI_SHAPING_TIME_AWARE 2
>
> +#define KSZ9477_PORT_MTI_QUEUE_CTRL_1 0x0915
> +#define KSZ9477_DEFAULT_WRR_WEIGHT 1
> +
> #define REG_PORT_MTI_HI_WATER_MARK 0x0916
> #define REG_PORT_MTI_LO_WATER_MARK 0x0918
>
> --
> 2.30.2
>
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