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kolibrios/drivers/usb/usb1_scheduler.inc

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; Implementation of periodic transaction scheduler for USB.
; Bandwidth dedicated to periodic transactions is limited, so
; different pipes should be scheduled as uniformly as possible.
; USB1 scheduler.
; Algorithm is simple:
; when adding a pipe, optimize the following quantity:
; * for every millisecond, take all bandwidth scheduled to periodic transfers,
; * calculate maximum over all milliseconds,
; * select a variant which minimizes that maximum;
; when removing a pipe, do nothing (except for bookkeeping).
; The caller must provide CONTROLLER_NAME define.
macro define_controller_name name
{
_hci_static_ep.SoftwarePart = name # _static_ep.SoftwarePart
_hci_static_ep.NextList = name # _static_ep.NextList
sizeof._hci_static_ep = sizeof. # name # _static_ep
}
; Select a list for a new pipe.
; in: esi -> usb_controller, maxpacket, type, interval can be found in the stack
; in: ecx = 2 * maximal interval = total number of periodic lists + 1
; in: edx -> {u|o}hci_static_ep for the first list
; in: eax -> byte past {u|o}hci_static_ep for the last list in the first group
; out: edx -> usb_static_ep for the selected list or zero if failed
proc usb1_select_interrupt_list
; inherit some variables from usb_open_pipe
virtual at ebp-12
.speed db ?
rb 3
.bandwidth dd ?
.target dd ?
dd ?
dd ?
.config_pipe dd ?
.endpoint dd ?
.maxpacket dd ?
.type dd ?
.interval dd ?
end virtual
push ebx edi ; save used registers to be stdcall
push eax ; save eax for checks in step 3
; 1. Only intervals 2^k ms can be supported.
; The core specification says that the real interval should not be greater
; than the interval given by the endpoint descriptor, but can be less.
; Determine the actual interval as 2^k ms.
mov eax, ecx
; 1a. Set [.interval] to 1 if it was zero; leave it as is otherwise
cmp [.interval], 1
adc [.interval], 0
; 1b. Divide ecx by two while it is strictly greater than [.interval].
@@:
shr ecx, 1
cmp [.interval], ecx
jb @b
; ecx = the actual interval
;
; For example, let ecx = 8, eax = 64.
; The scheduler space is 32 milliseconds,
; we need to schedule something every 8 ms;
; there are 8 variants: schedule at times 0,8,16,24,
; schedule at times 1,9,17,25,..., schedule at times 7,15,23,31.
; Now concentrate: there are three nested loops,
; * the innermost loop calculates the total periodic bandwidth scheduled
; in the given millisecond,
; * the intermediate loop calculates the maximum over all milliseconds
; in the given variant, that is the quantity we're trying to minimize,
; * the outermost loop checks all variants.
; 2. Calculate offset between the first list and the first list for the
; selected interval, in bytes; save in the stack for step 4.
sub eax, ecx
sub eax, ecx
imul eax, sizeof._hci_static_ep
push eax
imul ebx, ecx, sizeof._hci_static_ep
; 3. Select the best variant.
; 3a. The outermost loop.
; Prepare for the loop: set the current optimal bandwidth to maximum
; possible value (so that any variant will pass the first comparison),
; calculate delta for the intermediate loop.
or [.bandwidth], -1
.varloop:
; 3b. The intermediate loop.
; Prepare for the loop: set the maximum to be calculated to zero,
; save counter of the outermost loop.
xor edi, edi
push edx
virtual at esp
.cur_variant dd ? ; step 3b
.result_delta dd ? ; step 2
.group1_limit dd ? ; function prolog
end virtual
.calc_max_bandwidth:
; 3c. The innermost loop. Sum over all lists.
xor eax, eax
push edx
.calc_bandwidth:
add eax, [edx+_hci_static_ep.SoftwarePart+usb_static_ep.Bandwidth]
mov edx, [edx+_hci_static_ep.NextList]
test edx, edx
jnz .calc_bandwidth
pop edx
; 3d. The intermediate loop continued: update maximum.
cmp eax, edi
jb @f
mov edi, eax
@@:
; 3e. The intermediate loop continued: advance counter.
add edx, ebx
cmp edx, [.group1_limit]
jb .calc_max_bandwidth
; 3e. The intermediate loop done: restore counter of the outermost loop.
pop edx
; 3f. The outermost loop continued: if the current variant is
; better (maybe not strictly) then the previous optimum, update
; the optimal bandwidth and resulting list.
cmp edi, [.bandwidth]
ja @f
mov [.bandwidth], edi
mov [.target], edx
@@:
; 3g. The outermost loop continued: advance counter.
add edx, sizeof._hci_static_ep
dec ecx
jnz .varloop
; 4. Calculate bandwidth for the new pipe.
mov eax, [.maxpacket]
mov cl, [.speed]
mov ch, byte [.endpoint]
and ch, 80h
call calc_usb1_bandwidth
; 5. Get the pointer to the best list.
pop edx ; restore value from step 2
pop ecx ; purge stack var from prolog
add edx, [.target]
; 6. Check that bandwidth for the new pipe plus old bandwidth
; still fits to maximum allowed by the core specification, 90% of 12000 bits.
mov ecx, eax
add ecx, [.bandwidth]
cmp ecx, 10800
ja .no_bandwidth
; 7. Convert {o|u}hci_static_ep to usb_static_ep, update bandwidth and return.
add edx, _hci_static_ep.SoftwarePart
add [edx+usb_static_ep.Bandwidth], eax
pop edi ebx ; restore used registers to be stdcall
ret
.no_bandwidth:
dbgstr 'Periodic bandwidth limit reached'
xor edx, edx
pop edi ebx
ret
endp
; Pipe is removing, update the corresponding lists.
; We do not reorder anything, so just update book-keeping variable
; in the list header.
proc usb1_interrupt_list_unlink
virtual at esp
dd ? ; return address
.maxpacket dd ?
.lowspeed db ?
.direction db ?
rb 2
end virtual
; calculate bandwidth on the bus
mov eax, [.maxpacket]
mov ecx, dword [.lowspeed]
call calc_usb1_bandwidth
mov edx, [ebx+usb_pipe.BaseList]
; subtract pipe bandwidth
sub [edx+usb_static_ep.Bandwidth], eax
ret 8
endp
; Helper procedure for USB1 scheduler: calculate bandwidth on the bus.
; in: low 11 bits of eax = payload size in bytes
; in: cl = 0 - full-speed, nonzero - high-speed
; in: ch = 0 - OUT, nonzero - IN
; out: eax = maximal bandwidth in FS-bits
proc calc_usb1_bandwidth
and eax, (1 shl 11) - 1 ; get payload for one transaction
add eax, 3 ; add 3 bytes for other fields in data packet, PID+CRC16
test cl, cl
jnz .low_speed
; Multiply by 8 for bytes -> bits, by 7/6 to accomodate bit stuffing
; and by 401/400 for IN transfers to accomodate timers difference
; 9+107/300 for IN transfers, 9+1/3 for OUT transfers
; For 0 <= eax < 09249355h, floor(eax * 107/300) = floor(eax * 5B4E81B5h / 2^32).
; For 0 <= eax < 80000000h, floor(eax / 3) = floor(eax * 55555556h / 2^32).
mov edx, 55555556h
test ch, ch
jz @f
mov edx, 5B4E81B5h
@@:
lea ecx, [eax*9]
mul edx
; Add 93 extra bits: 39 bits for Token packet (8 for SYNC, 24 for token+address,
; 4 extra bits for possible bit stuffing in token+address, 3 for EOP),
; 18 bits for bus turn-around, 11 bits for SYNC+EOP in Data packet plus 1 bit
; for possible timers difference, 2 bits for inter-packet delay, 20 bits for
; Handshake packet, 2 bits for another inter-packet delay.
lea eax, [ecx+edx+93]
ret
.low_speed:
; Multiply by 8 for bytes -> bits, by 7/6 to accomodate bit stuffing,
; by 8 for LS -> FS and by 406/50 for IN transfers to accomodate timers difference.
; 75+59/75 for IN transfers, 74+2/3 for OUT transfers.
mov edx, 0AAAAAABh
test ch, ch
mov ecx, 74
jz @f
mov edx, 0C962FC97h
inc ecx
@@:
imul ecx, eax
mul edx
; Add 778 extra bits:
; 16 bits for PRE packet, 4 bits for hub delay, 8*39 bits for Token packet
; 8*18 bits for bus turn-around
; (406/50)*11 bits for SYNC+EOP in Data packet,
; 8*2 bits for inter-packet delay,
; 16 bits for PRE packet, 4 bits for hub delay, 8*20 bits for Handshake packet,
; 8*2 bits for another inter-packet delay.
lea eax, [ecx+edx+778]
ret
endp