With external calibration, SFF-8472 defines the received power
as a fourth order polynomial of the raw reading x:
RX_PWR(4) * x^4 + RX_PWR(3) * x^3 + RX_PWR(2) * x^2 +
RX_PWR(1) * x + RX_PWR(0)
The decoder computed RX_PWR(0) + x * (RX_PWR(1) + RX_PWR(2) + RX_PWR(3))
and ignored RX_PWR(4), so the reported power was wrong for modules
using the higher order coefficients.
Evaluate the polynomial in double precision and clamp the result
to the 16-bit range of the stored value, as converting an out of range
floating point value to an integer is undefined behavior.
Fixes: 0caf7f376b08 ("ethdev: support SFF-8472 module telemetry")
Cc: [email protected]
Signed-off-by: Roman Khromenok <[email protected]>
---
lib/ethdev/sff_8472.c | 27 ++++++++++++++++++---------
1 file changed, 18 insertions(+), 9 deletions(-)
diff --git a/lib/ethdev/sff_8472.c b/lib/ethdev/sff_8472.c
index cdb6ef1f7e..3c73a829a8 100644
--- a/lib/ethdev/sff_8472.c
+++ b/lib/ethdev/sff_8472.c
@@ -189,7 +189,8 @@ static float befloattoh(const uint8_t *source)
static void sff_8472_calibration(const uint8_t *data, struct sff_diags *sd)
{
unsigned long i;
- uint16_t rx_reading;
+ double rx_reading;
+ double rx_power;
/* Calibration should occur for all values (threshold and current) */
for (i = 0; i < RTE_DIM(sd->bias_cur); ++i) {
@@ -207,16 +208,24 @@ static void sff_8472_calibration(const uint8_t *data,
struct sff_diags *sd)
sd->sfp_temp[i] += A2_OFFSET_TO_OFF(SFF_A2_CAL_T_OFF);
/*
- * Apply calibration formula 2 (Rx Power only)
+ * Apply calibration formula 2 (Rx Power only):
+ * RX_PWR(4) * x^4 + RX_PWR(3) * x^3 + RX_PWR(2) * x^2 +
+ * RX_PWR(1) * x + RX_PWR(0)
*/
rx_reading = sd->rx_power[i];
- sd->rx_power[i] = A2_OFFSET_TO_RXPWRx(SFF_A2_CAL_RXPWR0);
- sd->rx_power[i] += rx_reading *
- A2_OFFSET_TO_RXPWRx(SFF_A2_CAL_RXPWR1);
- sd->rx_power[i] += rx_reading *
- A2_OFFSET_TO_RXPWRx(SFF_A2_CAL_RXPWR2);
- sd->rx_power[i] += rx_reading *
- A2_OFFSET_TO_RXPWRx(SFF_A2_CAL_RXPWR3);
+ rx_power = A2_OFFSET_TO_RXPWRx(SFF_A2_CAL_RXPWR4);
+ rx_power = rx_power * rx_reading +
A2_OFFSET_TO_RXPWRx(SFF_A2_CAL_RXPWR3);
+ rx_power = rx_power * rx_reading +
A2_OFFSET_TO_RXPWRx(SFF_A2_CAL_RXPWR2);
+ rx_power = rx_power * rx_reading +
A2_OFFSET_TO_RXPWRx(SFF_A2_CAL_RXPWR1);
+ rx_power = rx_power * rx_reading +
A2_OFFSET_TO_RXPWRx(SFF_A2_CAL_RXPWR0);
+
+ /* the result is stored in 0.1 uW units, out of range is not
representable */
+ if (!(rx_power > 0))
+ sd->rx_power[i] = 0;
+ else if (rx_power >= UINT16_MAX)
+ sd->rx_power[i] = UINT16_MAX;
+ else
+ sd->rx_power[i] = rx_power;
}
}
--
2.47.3
