firmware: card_emu: use Di in the waiting time

ISO 7816-3 section 10.2 defines WT = WI x 960 x Fi/f seconds,
store as etu, etu = Fi / (D x f) seconds, so the Fi cancels,
but the D does not:

	WT [etu] = WI x 960 x D

cemu dropped both (?!) -> WI x 960.
The old comment explains why Fi can be dropped, which is right, but
what about Di ?!
sniffer gets it right (wt_wi * 960UL * wt_d), so the two state machines
disagreed here again, by up to a factor of 64???!!?!!?

This was fixed in osmo-ccid-firmware in 066489d in 2020 but not ported
to st2.

Additionally the waiting time was only recalculated at the end of the ATR,
where D is still 1 by definition, so a PPS increasing D reprogrammed the
baud rate but left the waiting time untouched??!

etu duration shrinks with D by the same factor, wall clock WT is
independent of D, which is the whole point.
The old code decreased the waiting time by a factor of D:
after a PPS to D=8 the card emitted its NULL procedure byte at ~0.09s
instead of ~0.71s with a reader deadline of ~1.43s,
and the inactivity timeout fires 8x too early, which probably led to
unexplained wtime_exp errors.

Update wt when WI becomes known (end of ATR) and
where D changes (after the PPS response) + tests.

Change-Id: I4263176d6073029d01f9ff5b11a6311617956af6

firmware/libcommon/source/card_emu.c

@@ -386,6 +386,26 @@ static void emu_update_fidi(struct card_handle *ch)
 			   ch->num, rc);
 }
 
+/*! Calculate the WT from current WI and D.
+ *
+ * ISO 7816-3 10.2 defines WT = WI x 960 x Fi / f [seconds].
+ * Our waiting time is stored in units of etu = Fi / (D x f) seconds
+ * -> the Fi cancels out, but D does not.
+ *
+ *	WT [etu] = WI x 960 x D
+ *
+ * D is the value from ISO 7816-3 Table 8. Only 1..9 are defined,
+ * 0 and RFU range 10..15 have no D -> use D = 1 */
+static void emu_update_wt(struct card_handle *ch)
+{
+	uint8_t d = 1;
+
+	if (ch->D_index >= 1 && ch->D_index <= 9)
+		d = iso7816_3_di_table[ch->D_index];
+
+	ch->waiting_time = ch->wi * 960 * d;
+}
+
 /* Update the ISO 7816-3 TPDU receiver state */
 static void card_set_state(struct card_handle *ch,
 			   enum iso7816_3_card_state new_state)
@@ -505,11 +525,8 @@ static int tx_byte_atr(struct card_handle *ch)
 				}
 			}
 		}
-		/* update waiting time (see ISO 7816-3 10.2). We can drop the Fi
+		/* update the waiting time now that WI is known (see emu_update_wt) */
-		 * multiplier as we store the waiting time in units of 'etu', and
+		emu_update_wt(ch);
-		 * don't really care what the number of clock cycles or the absolute
-		 * wall clock time is */
-		ch->waiting_time = ch->wi * 960;
 		/* go to next state */
 		card_set_state(ch, ISO_S_WAIT_TPDU);
 		return 0;
@@ -675,6 +692,9 @@ static int tx_byte_pts(struct card_handle *ch)
 		card_emu_uart_wait_tx_idle(ch->uart_chan);
 		/* update baud rate generator with F/D */
 		emu_update_fidi(ch);
+		/* the waiting time is expressed in etu and scales with D, so it has
+		 * to be recomputed whenever D changes */
+		emu_update_wt(ch);
 		/* Wait for the next TPDU */
 		card_set_state(ch, ISO_S_WAIT_TPDU);
 		set_pts_state(ch, PTS_S_WAIT_REQ_PTSS);

firmware/test/card_emu_tests.c

@@ -396,12 +396,73 @@ const uint8_t pps[] = {
 	0xFF ^ 0b00010000// PCK
 };
 
-static void
+/* Fi/Di that is actually valid: Fi idx 9 (Fi=512) and Di idx 4 (Di=8)
-test_ppss(struct card_handle *ch)
+ * This tests calculating F/D ratio (512/8 = 64) and the calculation of the
+ * waiting time which scales with Di. */
+const uint8_t pps_fidi[] = {
+	0xFF,			// PPSS
+	0b00010000,		// PPS0: PPS1 present
+	0x94,			// PPS1: Fi index 9, Di index 4
+	0xFF ^ 0b00010000 ^ 0x94// PCK
+};
+
+/* Di 8 idx Di=12 (ISO 7816-3:2006 Table 8),:
+ * the ratio be 372/12 = 31, not 372*12. */
+const uint8_t pps_di12[] = {
+	0xFF,			// PPSS
+	0b00010000,		// PPS0: PPS1 present
+	0x18,			// PPS1: Fi index 1, Di index 8
+	0xFF ^ 0b00010000 ^ 0x18// PCK
+};
+
+/* Fi idx 5 Fi=1488 andDi=1 -> ratio 1488, needs all 11 bits of
+ * the US_FIDI.FI_DI_RATIO field. */
+const uint8_t pps_hi_ratio[] = {
+	0xFF,			// PPSS
+	0b00010000,		// PPS0: PPS1 present
+	0x51,			// PPS1: Fi index 5, Di index 1
+	0xFF ^ 0b00010000 ^ 0x51// PCK
+};
+
+/* Get a cemu status report to check the negotiated parameters
+ * This is the only way to get the waiting time from struct card_handle. */
+static void verify_status(struct card_handle *ch, uint8_t exp_f_index, uint8_t exp_d_index,
+			  uint32_t exp_waiting_time)
 {
-	reader_send_bytes(ch, pps, sizeof(pps));
+	struct usb_buffered_ep *bep = usb_get_buf_ep(PHONE_DATAIN);
-	get_and_verify_rctx_pps(pps, sizeof(pps));
+	struct cardemu_usb_msg_status *sts;
-	card_tx_verify_chars(ch, pps, sizeof(pps));
+	struct simtrace_msg_hdr *mh;
+	struct msgb *msg;
+
+	card_emu_report_status(ch, false);
+
+	assert(bep);
+	msg = msgb_dequeue_count(&bep->queue, &bep->queue_len);
+	assert(msg);
+	mh = (struct simtrace_msg_hdr *) msg->l1h;
+	assert(mh->msg_type == SIMTRACE_MSGT_BD_CEMU_STATUS);
+	sts = (struct cardemu_usb_msg_status *) msg->l2h;
+
+	printf("status: F_index=%u D_index=%u wi=%u waiting_time=%u\n",
+		sts->F_index, sts->D_index, sts->wi, sts->waiting_time);
+
+	assert(sts->F_index == exp_f_index);
+	assert(sts->D_index == exp_d_index);
+	/* WT = WI x 960 x D in etu, see ISO 7816-3 Section 10.2 */
+	assert(sts->waiting_time == exp_waiting_time);
+
+	usb_buf_free(msg);
+}
+
+static void
+test_ppss(struct card_handle *ch, const uint8_t *req, unsigned int req_len,
+	  uint8_t exp_f_index, uint8_t exp_d_index, uint32_t exp_waiting_time)
+{
+	printf("\n==> PPS exchange\n");
+	reader_send_bytes(ch, req, req_len);
+	get_and_verify_rctx_pps(req, req_len);
+	card_tx_verify_chars(ch, req, req_len);
+	verify_status(ch, exp_f_index, exp_d_index, exp_waiting_time);
 }
 
 /* READ RECORD (offset 0, 10 bytes) */
@@ -426,7 +487,12 @@ int main(int argc, char **argv)
 	io_start_card(ch);
 	card_tx_verify_chars(ch, NULL, 0);
 
-	test_ppss(ch);
+	/* WI is 10 so WT = 10 x 960 x D */
+	/* Fi/Di index 0/0 is invalid: the F/D ratio is rejected, D falls back to 1 */
+	test_ppss(ch, pps, sizeof(pps), 0, 0, 10 * 960 * 1);
+	test_ppss(ch, pps_fidi, sizeof(pps_fidi), 9, 4, 10 * 960 * 8);
+	test_ppss(ch, pps_di12, sizeof(pps_di12), 1, 8, 10 * 960 * 12);
+	test_ppss(ch, pps_hi_ratio, sizeof(pps_hi_ratio), 5, 1, 10 * 960 * 1);
 
 	for (i = 0; i < 2; i++) {
 		test_tpdu_reader2card(ch, tpdu_hdr_write_rec, tpdu_body_write_rec, sizeof(tpdu_body_write_rec));