can-calc-bit-timing: improve printing of bit timing parameters

This patch adds additional fields when printing the bit timing
parameters. Now the real bitrate the nominal and the real sample point
as well as the error of the sample point is displayed.

The output now looks like this:

Bit timing parameters for at91 with 100.000000 MHz ref clock
nominal                                 real Bitrt   nom  real SampP
Bitrate TQ[ns] PrS PhS1 PhS2 SJW BRP Bitrate Error SampP SampP Error     CAN_BR
1000000     50   7    7    5   1   5 1000000  0.0% 75.0% 75.0%  0.0% 0x00040664
 800000     50   8    8    8   1   5  800000  0.0% 80.0% 68.0% 15.0% 0x00040777
 500000    100   8    8    3   1  10  500000  0.0% 87.5% 85.0%  2.9% 0x00090772
 250000    250   6    7    2   1  25  250000  0.0% 87.5% 87.5%  0.0% 0x00180561
 125000    500   6    7    2   1  50  125000  0.0% 87.5% 87.5%  0.0% 0x00310561
 100000    500   8    8    3   1  50  100000  0.0% 87.5% 85.0%  2.9% 0x00310772
  50000   1250   6    7    2   1 125   50000  0.0% 87.5% 87.5%  0.0% 0x007c0561
  20000 ***bitrate not possible***
  10000 ***bitrate not possible***

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/can-calc-bit-timing.c b/can-calc-bit-timing.c
index 9db79e8cae29a43eec03225b427736eac4208d5f..1070b2991bce9587fe38d257fe6d3660092e8ac0 100644 (file)
--- a/can-calc-bit-timing.c
+++ b/can-calc-bit-timing.c
@@ -158,7 +158,7 @@ static void printf_btr_sja1000(struct can_bittiming *bt, int hdr)
 static void printf_btr_at91(struct can_bittiming *bt, int hdr)
 {
        if (hdr) {
-               printf("CAN_BR");
+               printf("%10s", "CAN_BR");
        } else {
                uint32_t br = ((bt->phase_seg2 - 1) |
                               ((bt->phase_seg1 - 1) << 4) |
@@ -390,6 +390,20 @@ static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt)
        return 0;
 }
 
+static __u32 get_cia_sample_point(__u32 bitrate)
+{
+       __u32 sampl_pt;
+
+       if (bitrate > 800000)
+               sampl_pt = 750;
+       else if (bitrate > 500000)
+               sampl_pt = 800;
+       else
+               sampl_pt = 875;
+
+       return sampl_pt;
+}
+
 static void print_bit_timing(const struct can_bittiming_const *btc,
                             __u32 bitrate, __u32 sample_point, __u32 ref_clk,
                             int quiet)
@@ -402,12 +416,15 @@ static void print_bit_timing(const struct can_bittiming_const *btc,
                .bitrate = bitrate,
                .sample_point = sample_point,
        };
-       long rate_error;
+       long rate_error, spt_error;
 
        if (!quiet) {
-               printf("Bit timing parameters for %s using %dHz\n",
-                      btc->name, ref_clk);
-               printf("Bitrate TQ[ns] PrS PhS1 PhS2 SJW BRP SampP Error ");
+               printf("Bit timing parameters for %s with %.6f MHz ref clock\n"
+                      "nominal                                 real Bitrt   nom  real SampP\n"
+                      "Bitrate TQ[ns] PrS PhS1 PhS2 SJW BRP Bitrate Error SampP SampP Error ",
+                      btc->name,
+                      ref_clk / 1000000.0);
+
                btc->printf_btr(&bt, 1);
                printf("\n");
        }
@@ -417,13 +434,29 @@ static void print_bit_timing(const struct can_bittiming_const *btc,
                return;
        }
 
+       /* get nominal sample point */
+       if (!sample_point)
+               sample_point = get_cia_sample_point(bitrate);
+
        rate_error = abs((__s32)(bitrate - bt.bitrate));
+       spt_error = abs((__s32)(sample_point - bt.sample_point));
+
+       printf("%7d "
+              "%6d %3d %4d %4d "
+              "%3d %3d "
+              "%7d %4.1f%% "
+              "%4.1f%% %4.1f%% %4.1f%% ",
+              bitrate,
+              bt.tq, bt.prop_seg, bt.phase_seg1, bt.phase_seg2,
+              bt.sjw, bt.brp,
+
+              bt.bitrate,
+              100.0 * rate_error / bitrate,
+
+              sample_point / 10.0,
+              bt.sample_point / 10.0,
+              100.0 * spt_error / sample_point);
 
-       printf("%7d %6d %3d %4d %4d %3d %3d %2d.%d%% %4.1f%% ",
-              bitrate, bt.tq, bt.prop_seg, bt.phase_seg1,
-              bt.phase_seg2, bt.sjw, bt.brp,
-              bt.sample_point / 10, bt.sample_point % 10,
-              100.0 * rate_error / bitrate);
        btc->printf_btr(&bt, 0);
        printf("\n");
 }