Re: [PATCH 4/4] net: dsa: mv88e6xxx: add PTP support for MV88E6250 family
From: Richard Cochran <richardcochran@gmail.com>
Date: 2019-07-30 16:00:38
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On Tue, Jul 30, 2019 at 12:04:29PM +0200, Hubert Feurstein wrote:
quoted hunk ↗ jump to hunk
diff --git a/drivers/net/dsa/mv88e6xxx/ptp.c b/drivers/net/dsa/mv88e6xxx/ptp.c index 768d256f7c9f..51cdf4712517 100644 --- a/drivers/net/dsa/mv88e6xxx/ptp.c +++ b/drivers/net/dsa/mv88e6xxx/ptp.c@@ -15,11 +15,38 @@ #include "hwtstamp.h" #include "ptp.h" -/* Raw timestamps are in units of 8-ns clock periods. */ -#define CC_SHIFT 28 -#define CC_MULT (8 << CC_SHIFT) -#define CC_MULT_NUM (1 << 9) -#define CC_MULT_DEM 15625ULL +/* The adjfine API clamps ppb between [-32,768,000, 32,768,000], and
That is not true.
+ * therefore scaled_ppm between [-2,147,483,648, 2,147,483,647]. + * Set the maximum supported ppb to a round value smaller than the maximum. + * + * Percentually speaking, this is a +/- 0.032x adjustment of the + * free-running counter (0.968x to 1.032x). + */ +#define MV88E6XXX_MAX_ADJ_PPB 32000000
I had set an arbitrary limit of 1000 ppm. I can't really see any point in raising the limit.
quoted hunk ↗ jump to hunk
+/* Family MV88E6250: + * Raw timestamps are in units of 10-ns clock periods. + * + * clkadj = scaled_ppm * 10*2^28 / (10^6 * 2^16) + * simplifies to + * clkadj = scaled_ppm * 2^7 / 5^5 + */ +#define MV88E6250_CC_SHIFT 28 +#define MV88E6250_CC_MULT (10 << MV88E6250_CC_SHIFT) +#define MV88E6250_CC_MULT_NUM (1 << 7) +#define MV88E6250_CC_MULT_DEM 3125ULL + +/* Other families: + * Raw timestamps are in units of 8-ns clock periods. + * + * clkadj = scaled_ppm * 8*2^28 / (10^6 * 2^16) + * simplifies to + * clkadj = scaled_ppm * 2^9 / 5^6 + */ +#define MV88E6XXX_CC_SHIFT 28 +#define MV88E6XXX_CC_MULT (8 << MV88E6XXX_CC_SHIFT) +#define MV88E6XXX_CC_MULT_NUM (1 << 9) +#define MV88E6XXX_CC_MULT_DEM 15625ULL #define TAI_EVENT_WORK_INTERVAL msecs_to_jiffies(100)@@ -179,24 +206,14 @@ static void mv88e6352_tai_event_work(struct work_struct *ugly) static int mv88e6xxx_ptp_adjfine(struct ptp_clock_info *ptp, long scaled_ppm) { struct mv88e6xxx_chip *chip = ptp_to_chip(ptp); - int neg_adj = 0; - u32 diff, mult; - u64 adj; + s64 adj; - if (scaled_ppm < 0) { - neg_adj = 1; - scaled_ppm = -scaled_ppm; - }
Please don't re-write this logic. It is written like that for a reason.
- mult = CC_MULT; - adj = CC_MULT_NUM; - adj *= scaled_ppm; - diff = div_u64(adj, CC_MULT_DEM);
Just substitute CC_MULT* with your new chip->ptp_cc_mult* and leave the rest alone. Thanks, Richard