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Message-ID: <20200624130318.GD7247@localhost>
Date: Wed, 24 Jun 2020 06:03:18 -0700
From: Richard Cochran <richardcochran@...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>,
Kamil Alkhouri <kamil.alkhouri@...offenburg.de>,
ilias.apalodimas@...aro.org
Subject: Re: [RFC PATCH 3/9] net: dsa: hellcreek: Add PTP clock support
On Thu, Jun 18, 2020 at 08:40:23AM +0200, Kurt Kanzenbach wrote:
> diff --git a/drivers/net/dsa/hirschmann/hellcreek.h b/drivers/net/dsa/hirschmann/hellcreek.h
> index a08a10cb5ab7..2d4422fd2567 100644
> --- a/drivers/net/dsa/hirschmann/hellcreek.h
> +++ b/drivers/net/dsa/hirschmann/hellcreek.h
> @@ -234,10 +234,17 @@ struct hellcreek_fdb_entry {
> struct hellcreek {
> struct device *dev;
> struct dsa_switch *ds;
> + struct ptp_clock *ptp_clock;
> + struct ptp_clock_info ptp_clock_info;
> struct hellcreek_port ports[4];
> + struct delayed_work overflow_work;
> spinlock_t reg_lock; /* Switch IP register lock */
> + spinlock_t ptp_lock; /* PTP IP register lock */
Why use a spin lock and not a mutex?
> void __iomem *base;
> + void __iomem *ptp_base;
> u8 *vidmbrcfg; /* vidmbrcfg shadow */
> + u64 seconds; /* PTP seconds */
> + u64 last_ts; /* Used for overflow detection */
> size_t fdb_entries;
> };
> +static int hellcreek_ptp_gettime(struct ptp_clock_info *ptp,
> + struct timespec64 *ts)
> +{
> + struct hellcreek *hellcreek = ptp_to_hellcreek(ptp);
> + u64 ns;
> +
> + spin_lock(&hellcreek->ptp_lock);
Won't a mutex do here instead?
> + ns = __hellcreek_ptp_gettime(hellcreek);
> + spin_unlock(&hellcreek->ptp_lock);
> +
> + *ts = ns_to_timespec64(ns);
> +
> + return 0;
> +}
> +static int hellcreek_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta)
> +{
> + struct hellcreek *hellcreek = ptp_to_hellcreek(ptp);
> + u16 negative = 0, counth, countl;
> + u32 count_val;
> +
> + /* If the offset is larger than IP-Core slow offset resources. Don't
> + * concider slow adjustment. Rather, add the offset directly to the
consider
> + * current time
> + */
> + if (abs(delta) > MAX_SLOW_OFFSET_ADJ) {
> + struct timespec64 now, then = ns_to_timespec64(delta);
> +
> + hellcreek_ptp_gettime(ptp, &now);
> + now = timespec64_add(now, then);
> + hellcreek_ptp_settime(ptp, &now);
> +
> + return 0;
> + }
> +
> + if (delta < 0) {
> + negative = 1;
> + delta = -delta;
> + }
> +
> + /* 'count_val' does not exceed the maximum register size (2^30) */
> + count_val = div_s64(delta, MAX_NS_PER_STEP);
> +
> + counth = (count_val & 0xffff0000) >> 16;
> + countl = count_val & 0xffff;
> +
> + negative = (negative << 15) & 0x8000;
> +
> + spin_lock(&hellcreek->ptp_lock);
> +
> + /* Set offset write register */
> + hellcreek_ptp_write(hellcreek, negative, PR_CLOCK_OFFSET_C);
> + hellcreek_ptp_write(hellcreek, MAX_NS_PER_STEP, PR_CLOCK_OFFSET_C);
> + hellcreek_ptp_write(hellcreek, MIN_CLK_CYCLES_BETWEEN_STEPS,
> + PR_CLOCK_OFFSET_C);
> + hellcreek_ptp_write(hellcreek, countl, PR_CLOCK_OFFSET_C);
> + hellcreek_ptp_write(hellcreek, counth, PR_CLOCK_OFFSET_C);
> +
> + spin_unlock(&hellcreek->ptp_lock);
> +
> + return 0;
> +}
> +int hellcreek_ptp_setup(struct hellcreek *hellcreek)
> +{
> + u16 status;
> +
> + /* Set up the overflow work */
> + INIT_DELAYED_WORK(&hellcreek->overflow_work,
> + hellcreek_ptp_overflow_check);
> +
> + /* Setup PTP clock */
> + hellcreek->ptp_clock_info.owner = THIS_MODULE;
> + snprintf(hellcreek->ptp_clock_info.name,
> + sizeof(hellcreek->ptp_clock_info.name),
> + dev_name(hellcreek->dev));
> +
> + /* IP-Core can add up to 0.5 ns per 8 ns cycle, which means
> + * accumulator_overflow_rate shall not exceed 62.5 MHz (which adjusts
> + * the nominal frequency by 6.25%)
> + */
> + hellcreek->ptp_clock_info.max_adj = 62500000;
> + hellcreek->ptp_clock_info.n_alarm = 0;
> + hellcreek->ptp_clock_info.n_pins = 0;
> + hellcreek->ptp_clock_info.n_ext_ts = 0;
> + hellcreek->ptp_clock_info.n_per_out = 0;
> + hellcreek->ptp_clock_info.pps = 0;
> + hellcreek->ptp_clock_info.adjfine = hellcreek_ptp_adjfine;
> + hellcreek->ptp_clock_info.adjtime = hellcreek_ptp_adjtime;
> + hellcreek->ptp_clock_info.gettime64 = hellcreek_ptp_gettime;
> + hellcreek->ptp_clock_info.settime64 = hellcreek_ptp_settime;
> + hellcreek->ptp_clock_info.enable = hellcreek_ptp_enable;
> +
> + hellcreek->ptp_clock = ptp_clock_register(&hellcreek->ptp_clock_info,
> + hellcreek->dev);
> + if (IS_ERR(hellcreek->ptp_clock))
> + return PTR_ERR(hellcreek->ptp_clock);
The ptp_clock_register() can also return NULL:
* Returns a valid pointer on success or PTR_ERR on failure. If PHC
* support is missing at the configuration level, this function
* returns NULL, and drivers are expected to gracefully handle that
* case separately.
> +
> + /* Enable the offset correction process, if no offset correction is
> + * already taking place
> + */
> + status = hellcreek_ptp_read(hellcreek, PR_CLOCK_STATUS_C);
> + if (!(status & PR_CLOCK_STATUS_C_OFS_ACT))
> + hellcreek_ptp_write(hellcreek,
> + status | PR_CLOCK_STATUS_C_ENA_OFS,
> + PR_CLOCK_STATUS_C);
> +
> + /* Enable the drift correction process */
> + hellcreek_ptp_write(hellcreek, status | PR_CLOCK_STATUS_C_ENA_DRIFT,
> + PR_CLOCK_STATUS_C);
> +
> + schedule_delayed_work(&hellcreek->overflow_work,
> + HELLCREEK_OVERFLOW_PERIOD);
> +
> + return 0;
> +}
Thanks,
Richard
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