usbdux: usbduxsigma: added soft interval mode in the firmware

urb->interval is ignored in xhci drivers. Instead, the firmware
has an interval counter and transmits data at this interval.
The uframes in-between are zero length packets. In order to be
backward compatible with older kernels which support only USB 2.0
and 1.1 there are two ADC modes in the firmware. The old one which
assumes that the interval is established by the host (urb->interval)
and the new one where the interval value is transmitted to the
firmware.
Signed-off-by: Bernd Porr <mail@berndporr.me.uk>
Signed-off-by: Kyle McMartin <kyle@kernel.org>

usbdux/usbduxsigma_firmware.asm

@@ -39,6 +39,8 @@
 	.equ	DPTRL,85H
 	.equ	DPTRH,86h
 	.equ	ASYNC_ON,87h
+	.equ	INTERVAL,88h	; uframe/frame interval
+	.equ	INTCTR,89h	; interval counter
 
 ;;; actual code
 	.org	0000h		; after reset the processor starts here
@@ -547,6 +549,17 @@ sof_isr:
 
 	clr	IE.7		; make sure that no other int's disturbe us
 
+	mov	r0,#INTCTR	; interval counter
+	mov	a,@r0		; get the value
+	dec	a		; decrement
+	mov	@r0,a		; save it again
+	jz	sof_adc		; we do ADC functions
+	ljmp	epfull		; we skip all adc functions
+	
+sof_adc:
+	mov	r1,#INTERVAL	; get the interval
+	mov	a,@r1		; get it
+	mov	@r0,a		; save it in the counter
 	mov	a,EP2468STAT
 	anl	a,#20H		; full?
 	jnz	epfull		; EP6-buffer is full
@@ -762,6 +775,7 @@ ep1out_jmp:
 	sjmp	nothing		; a=6
 	sjmp	pwm_on		; a=7
 	sjmp	pwm_off		; a=8
+	sjmp	startadcint	; a=9
 
 nothing:
 	ljmp	over_da
@@ -790,12 +804,25 @@ initsgADchannel:
 		
 	sjmp	over_da
 
+startadcint:
+	mov	dptr,#0e781h	; FIFO buffer of EP1OUT from 2nd byte
+
+	movx	a,@dptr		; interval is the 1st byte
+	inc	dptr		; data pointer
+	sjmp	startadc2	; the other paramters as with startadc
 	
 ;;; config AD:
 ;;; we write to the registers of the A/D converter
 startadc:
 	mov	dptr,#0e781h	; FIFO buffer of EP1OUT from 2nd byte
 
+	mov	a,#1		; interval is 1 here all the time
+startadc2:	
+	mov	r0,#INTERVAL	; set it
+	mov	@r0,a
+	mov	r0,#INTCTR	; the counter is also just one
+	mov	@r0,a
+
 	movx	a,@dptr		; get length of channel list
 	inc	dptr
 	mov	r0,#MAXSMPL