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via-cuda: Add support for Egret system controller
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The Egret system controller was the predecessor to the Cuda and the
differences are minor.

On Cuda, byte acknowledgement requires one transition of the TACK
signal; on Egret two are needed. On Cuda, TIP is active low; on Egret
it is active high. And Cuda raises certain interrupts that Egret omits.

Accomodating these differences complicates the Cuda driver slightly
but avoids a lot of duplication (see next patch).

Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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Finn Thain authored and Michael Ellerman committed Feb 7, 2017
1 parent 97ced1a commit d23eee8
Showing 1 changed file with 134 additions and 21 deletions.
155 changes: 134 additions & 21 deletions drivers/macintosh/via-cuda.c
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Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
/*
* Device driver for the via-cuda on Apple Powermacs.
* Device driver for the Cuda and Egret system controllers found on PowerMacs
* and 68k Macs.
*
* The VIA (versatile interface adapter) interfaces to the CUDA,
* a 6805 microprocessor core which controls the ADB (Apple Desktop
* Bus) which connects to the keyboard and mouse. The CUDA also
* controls system power and the RTC (real time clock) chip.
* The Cuda or Egret is a 6805 microcontroller interfaced to the 6522 VIA.
* This MCU controls system power, Parameter RAM, Real Time Clock and the
* Apple Desktop Bus (ADB) that connects to the keyboard and mouse.
*
* Copyright (C) 1996 Paul Mackerras.
*/
@@ -50,10 +50,27 @@ static DEFINE_SPINLOCK(cuda_lock);
#define IER (14*RS) /* Interrupt enable register */
#define ANH (15*RS) /* A-side data, no handshake */

/* Bits in B data register: all active low */
#define TREQ 0x08 /* Transfer request (input) */
#define TACK 0x10 /* Transfer acknowledge (output) */
#define TIP 0x20 /* Transfer in progress (output) */
/*
* When the Cuda design replaced the Egret, some signal names and
* logic sense changed. They all serve the same purposes, however.
*
* VIA pin | Egret pin
* ----------------+------------------------------------------
* PB3 (input) | Transceiver session (active low)
* PB4 (output) | VIA full (active high)
* PB5 (output) | System session (active high)
*
* VIA pin | Cuda pin
* ----------------+------------------------------------------
* PB3 (input) | Transfer request (active low)
* PB4 (output) | Byte acknowledge (active low)
* PB5 (output) | Transfer in progress (active low)
*/

/* Bits in Port B data register */
#define TREQ 0x08 /* Transfer request */
#define TACK 0x10 /* Transfer acknowledge */
#define TIP 0x20 /* Transfer in progress */

/* Bits in ACR */
#define SR_CTRL 0x1c /* Shift register control bits */
@@ -65,19 +82,49 @@ static DEFINE_SPINLOCK(cuda_lock);
#define IER_CLR 0 /* clear bits in IER */
#define SR_INT 0x04 /* Shift register full/empty */

/* Duration of byte acknowledgement pulse (us) */
#define EGRET_TACK_ASSERTED_DELAY 300
#define EGRET_TACK_NEGATED_DELAY 400

/* Interval from interrupt to start of session (us) */
#define EGRET_SESSION_DELAY 450

#ifdef CONFIG_PPC
#define mcu_is_egret false
#else
static bool mcu_is_egret;
#endif

static inline bool TREQ_asserted(u8 portb)
{
return !(portb & TREQ);
}

static inline void assert_TIP(void)
{
out_8(&via[B], in_8(&via[B]) & ~TIP);
if (mcu_is_egret) {
udelay(EGRET_SESSION_DELAY);
out_8(&via[B], in_8(&via[B]) | TIP);
} else
out_8(&via[B], in_8(&via[B]) & ~TIP);
}

static inline void assert_TIP_and_TACK(void)
{
if (mcu_is_egret) {
udelay(EGRET_SESSION_DELAY);
out_8(&via[B], in_8(&via[B]) | TIP | TACK);
} else
out_8(&via[B], in_8(&via[B]) & ~(TIP | TACK));
}

static inline void assert_TACK(void)
{
out_8(&via[B], in_8(&via[B]) & ~TACK);
if (mcu_is_egret) {
udelay(EGRET_TACK_NEGATED_DELAY);
out_8(&via[B], in_8(&via[B]) | TACK);
} else
out_8(&via[B], in_8(&via[B]) & ~TACK);
}

static inline void toggle_TACK(void)
@@ -87,12 +134,20 @@ static inline void toggle_TACK(void)

static inline void negate_TACK(void)
{
out_8(&via[B], in_8(&via[B]) | TACK);
if (mcu_is_egret) {
udelay(EGRET_TACK_ASSERTED_DELAY);
out_8(&via[B], in_8(&via[B]) & ~TACK);
} else
out_8(&via[B], in_8(&via[B]) | TACK);
}

static inline void negate_TIP_and_TACK(void)
{
out_8(&via[B], in_8(&via[B]) | TIP | TACK);
if (mcu_is_egret) {
udelay(EGRET_TACK_ASSERTED_DELAY);
out_8(&via[B], in_8(&via[B]) & ~(TIP | TACK));
} else
out_8(&via[B], in_8(&via[B]) | TIP | TACK);
}

static enum cuda_state {
@@ -155,6 +210,7 @@ int __init find_via_cuda(void)

via = via1;
cuda_state = idle;
mcu_is_egret = false;

err = cuda_init_via();
if (err) {
@@ -251,7 +307,7 @@ static int __init via_cuda_start(void)
return -EAGAIN;
}

pr_info("Macintosh CUDA driver v0.5 for Unified ADB.\n");
pr_info("Macintosh Cuda and Egret driver.\n");

cuda_fully_inited = 1;
return 0;
@@ -276,6 +332,33 @@ cuda_probe(void)
}
#endif /* CONFIG_ADB */

static int __init sync_egret(void)
{
if (TREQ_asserted(in_8(&via[B]))) {
/* Complete the inbound transfer */
assert_TIP_and_TACK();
while (1) {
negate_TACK();
mdelay(1);
(void)in_8(&via[SR]);
assert_TACK();
if (!TREQ_asserted(in_8(&via[B])))
break;
}
negate_TIP_and_TACK();
} else if (in_8(&via[B]) & TIP) {
/* Terminate the outbound transfer */
negate_TACK();
assert_TACK();
mdelay(1);
negate_TIP_and_TACK();
}
/* Clear shift register interrupt */
if (in_8(&via[IFR]) & SR_INT)
(void)in_8(&via[SR]);
return 0;
}

#define WAIT_FOR(cond, what) \
do { \
int x; \
@@ -291,17 +374,22 @@ cuda_probe(void)
static int
__init cuda_init_via(void)
{
out_8(&via[DIRB], (in_8(&via[DIRB]) | TACK | TIP) & ~TREQ); /* TACK & TIP out */
negate_TIP_and_TACK();
out_8(&via[ACR] ,(in_8(&via[ACR]) & ~SR_CTRL) | SR_EXT); /* SR data in */
(void)in_8(&via[SR]); /* clear any left-over data */
#ifdef CONFIG_PPC
out_8(&via[IER], 0x7f); /* disable interrupts from VIA */
(void)in_8(&via[IER]);
#else
out_8(&via[IER], SR_INT); /* disable SR interrupt from VIA */
#endif

out_8(&via[DIRB], (in_8(&via[DIRB]) | TACK | TIP) & ~TREQ); /* TACK & TIP out */
out_8(&via[ACR], (in_8(&via[ACR]) & ~SR_CTRL) | SR_EXT); /* SR data in */
(void)in_8(&via[SR]); /* clear any left-over data */

if (mcu_is_egret)
return sync_egret();

negate_TIP_and_TACK();

/* delay 4ms and then clear any pending interrupt */
mdelay(4);
(void)in_8(&via[SR]);
@@ -453,7 +541,10 @@ cuda_start(void)
/* set the shift register to shift out and send a byte */
out_8(&via[ACR], in_8(&via[ACR]) | SR_OUT);
out_8(&via[SR], current_req->data[data_index++]);
assert_TIP();
if (mcu_is_egret)
assert_TIP_and_TACK();
else
assert_TIP();
cuda_state = sent_first_byte;
}

@@ -500,16 +591,17 @@ cuda_interrupt(int irq, void *arg)

switch (cuda_state) {
case idle:
/* CUDA has sent us the first byte of data - unsolicited */
/* System controller has unsolicited data for us */
(void)in_8(&via[SR]);
idle_state:
assert_TIP();
cuda_state = reading;
reply_ptr = cuda_rbuf;
reading_reply = 0;
break;

case awaiting_reply:
/* CUDA has sent us the first byte of data of a reply */
/* System controller has reply data for us */
(void)in_8(&via[SR]);
assert_TIP();
cuda_state = reading;
@@ -524,9 +616,14 @@ cuda_interrupt(int irq, void *arg)
(void)in_8(&via[SR]);
negate_TIP_and_TACK();
cuda_state = idle;
/* Egret does not raise an "aborted" interrupt */
if (mcu_is_egret)
goto idle_state;
} else {
out_8(&via[SR], current_req->data[data_index++]);
toggle_TACK();
if (mcu_is_egret)
assert_TACK();
cuda_state = sending;
}
break;
@@ -550,6 +647,8 @@ cuda_interrupt(int irq, void *arg)
} else {
out_8(&via[SR], req->data[data_index++]);
toggle_TACK();
if (mcu_is_egret)
assert_TACK();
}
break;

@@ -560,16 +659,24 @@ cuda_interrupt(int irq, void *arg)
else
*reply_ptr++ = in_8(&via[SR]);
if (!TREQ_asserted(status)) {
if (mcu_is_egret)
assert_TACK();
/* that's all folks */
negate_TIP_and_TACK();
cuda_state = read_done;
/* Egret does not raise a "read done" interrupt */
if (mcu_is_egret)
goto read_done_state;
} else {
toggle_TACK();
if (mcu_is_egret)
negate_TACK();
}
break;

case read_done:
(void)in_8(&via[SR]);
read_done_state:
if (reading_reply) {
req = current_req;
req->reply_len = reply_ptr - req->reply;
@@ -645,6 +752,12 @@ cuda_input(unsigned char *buf, int nb)
#endif /* CONFIG_ADB */
break;

case TIMER_PACKET:
/* Egret sends these periodically. Might be useful as a 'heartbeat'
* to trigger a recovery for the VIA shift register errata.
*/
break;

default:
print_hex_dump(KERN_INFO, "cuda_input: ", DUMP_PREFIX_NONE, 32, 1,
buf, nb, false);

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