Date:   Sat, 22 Aug 2020 17:39:22 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Kurt Kanzenbach <kurt@...utronix.de>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Richard Cochran <richardcochran@...il.com>,
        Kamil Alkhouri <kamil.alkhouri@...offenburg.de>,
        ilias.apalodimas@...aro.org
Subject: Re: [PATCH v3 5/8] net: dsa: hellcreek: Add TAPRIO offloading support

Hi Kurt,

On Thu, Aug 20, 2020 at 10:11:15AM +0200, Kurt Kanzenbach wrote:
> The switch has support for the 802.1Qbv Time Aware Shaper (TAS). Traffic
> schedules may be configured individually on each front port. Each port has eight
> egress queues. The traffic is mapped to a traffic class respectively via the PCP
> field of a VLAN tagged frame.
> 
> The TAPRIO Qdisc already implements that. Therefore, this interface can simply
> be reused. Add .port_setup_tc() accordingly.
> 
> The activation of a schedule on a port is split into two parts:
> 
>  * Programming the necessary gate control list (GCL)
>  * Setup hrtimer for starting the schedule
> 
> The hardware supports starting a schedule up to eight seconds in the future. The
> TAPRIO interface provides an absolute base time. Therefore, hrtimers are
> leveraged.
> 
> Signed-off-by: Kurt Kanzenbach <kurt@...utronix.de>
> ---
>  drivers/net/dsa/hirschmann/hellcreek.c | 294 +++++++++++++++++++++++++
>  drivers/net/dsa/hirschmann/hellcreek.h |  21 ++
>  2 files changed, 315 insertions(+)
> 
> diff --git a/drivers/net/dsa/hirschmann/hellcreek.c b/drivers/net/dsa/hirschmann/hellcreek.c
> index 745ca60342b4..e5b54f42c635 100644
> --- a/drivers/net/dsa/hirschmann/hellcreek.c
> +++ b/drivers/net/dsa/hirschmann/hellcreek.c
> @@ -22,7 +22,9 @@
>  #include <linux/spinlock.h>
>  #include <linux/delay.h>
>  #include <linux/ktime.h>
> +#include <linux/time.h>
>  #include <net/dsa.h>
> +#include <net/pkt_sched.h>
>  
>  #include "hellcreek.h"
>  #include "hellcreek_ptp.h"
> @@ -153,6 +155,15 @@ static void hellcreek_select_vlan(struct hellcreek *hellcreek, int vid,
>  	hellcreek_write(hellcreek, val, HR_VIDCFG);
>  }
>  
> +static void hellcreek_select_tgd(struct hellcreek *hellcreek, int port)
> +{
> +	u16 val = 0;
> +
> +	val |= port << TR_TGDSEL_TDGSEL_SHIFT;
> +
> +	hellcreek_write(hellcreek, val, TR_TGDSEL);
> +}
> +
>  static int hellcreek_wait_until_ready(struct hellcreek *hellcreek)
>  {
>  	u16 val;
> @@ -958,6 +969,24 @@ static void __hellcreek_setup_tc_identity_mapping(struct hellcreek *hellcreek)
>  	}
>  }
>  
> +static void hellcreek_setup_tc_mapping(struct hellcreek *hellcreek,
> +				       struct net_device *netdev)
> +{
> +	int i, j;
> +
> +	/* Setup mapping between traffic classes and port queues. */
> +	for (i = 0; i < netdev_get_num_tc(netdev); ++i) {
> +		for (j = 0; j < netdev->tc_to_txq[i].count; ++j) {
> +			const int queue = j + netdev->tc_to_txq[i].offset;
> +
> +			hellcreek_select_prio(hellcreek, i);
> +			hellcreek_write(hellcreek,
> +					queue << HR_PRTCCFG_PCP_TC_MAP_SHIFT,
> +					HR_PRTCCFG);
> +		}
> +	}
> +}

What other driver have you seen that does this?

> +
> +static int hellcreek_port_set_schedule(struct dsa_switch *ds, int port,
> +				       const struct tc_taprio_qopt_offload *taprio)
> +{
> +	struct net_device *netdev = dsa_to_port(ds, port)->slave;
> +	struct hellcreek *hellcreek = ds->priv;
> +	struct hellcreek_port *hellcreek_port;
> +	struct hellcreek_schedule *schedule;
> +	unsigned long flags;
> +	ktime_t start;
> +	u16 ctrl;
> +
> +	hellcreek_port = &hellcreek->ports[port];
> +
> +	/* Convert taprio data to hellcreek schedule */
> +	schedule = hellcreek_taprio_to_schedule(taprio);
> +	if (IS_ERR(schedule))
> +		return PTR_ERR(schedule);
> +
> +	dev_dbg(hellcreek->dev, "Configure traffic schedule on port %d\n",
> +		port);
> +
> +	/* Cancel an in flight timer */
> +	hrtimer_cancel(&hellcreek_port->cycle_start_timer);
> +
> +	spin_lock_irqsave(&hellcreek->reg_lock, flags);
> +
> +	if (hellcreek_port->current_schedule) {
> +		kfree(hellcreek_port->current_schedule->entries);
> +		kfree(hellcreek_port->current_schedule);
> +	}
> +
> +	hellcreek_port->current_schedule = schedule;
> +
> +	/* First select port */
> +	hellcreek_select_tgd(hellcreek, port);
> +
> +	/* Setup traffic class <-> queue mapping */
> +	hellcreek_setup_tc_mapping(hellcreek, netdev);
> +
> +	/* Enable gating and set the admin state to forward everything in the
> +	 * mean time
> +	 */
> +	ctrl = (0xff << TR_TGDCTRL_ADMINGATESTATES_SHIFT) | TR_TGDCTRL_GATE_EN;
> +	hellcreek_write(hellcreek, ctrl, TR_TGDCTRL);
> +
> +	/* Cancel pending schedule */
> +	hellcreek_write(hellcreek, 0x00, TR_ESTCMD);
> +
> +	/* Setup a new schedule */
> +	hellcreek_setup_gcl(hellcreek, port, schedule);
> +
> +	/* Configure cycle time */
> +	hellcreek_set_cycle_time(hellcreek, schedule);
> +
> +	/* Setup timer for schedule switch: The IP core only allows to set a
> +	 * cycle start timer 8 seconds in the future. This is why we setup the
> +	 * hritmer to base_time - 5 seconds. Then, we have enough time to
> +	 * activate IP core's EST timer.
> +	 */
> +	start = ktime_sub_ns(schedule->base_time, (u64)5 * NSEC_PER_SEC);
> +	hrtimer_start_range_ns(&hellcreek_port->cycle_start_timer, start,
> +			       NSEC_PER_SEC, HRTIMER_MODE_ABS);
> +
> +	spin_unlock_irqrestore(&hellcreek->reg_lock, flags);
> +
> +	return 0;
> +}

Thanks,
-Vladimir

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