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macintosh/via-macii: Poll the device most likely to respond

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Poll the most recently polled device by default, rather than the lowest
device address that happens to be enabled in autopoll_devs. This improves
input latency. Re-use macii_queue_poll() rather than duplicate that logic.
This eliminates a static struct and function.

Fixes: d95fd5fce8 ("m68k: Mac II ADB fixes") # v5.0+
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/5836f80886ebcfbe5be5fb7e0dc49feed6469712.1593318192.git.fthain@telegraphics.com.au
This commit is contained in:
Finn Thain 2020-06-28 14:23:12 +10:00 committed by Michael Ellerman
parent 59ea38f6b3
commit f93bfeb552
1 changed files with 53 additions and 46 deletions
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99
drivers/macintosh/via-macii.c
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@ -77,6 +77,10 @@ static volatile unsigned char *via;
#define ST_ODD 0x20 /* ADB state: odd data byte */
#define ST_IDLE 0x30 /* ADB state: idle, nothing to send */
/* ADB command byte structure */
#define ADDR_MASK 0xF0
#define CMD_MASK 0x0F
static int macii_init_via(void);
static void macii_start(void);
static irqreturn_t macii_interrupt(int irq, void *arg);
@ -117,7 +121,8 @@ static int reply_len; /* number of bytes received in reply_buf or req->reply */
static int status; /* VIA's ADB status bits captured upon interrupt */
static int last_status; /* status bits as at previous interrupt */
static int srq_asserted; /* have to poll for the device that asserted it */
static int command_byte; /* the most recent command byte transmitted */
static u8 last_cmd; /* the most recent command byte transmitted */
static u8 last_poll_cmd; /* the most recent Talk R0 command byte transmitted */
static int autopoll_devs; /* bits set are device addresses to be polled */
/* Check for MacII style ADB */
@ -179,35 +184,49 @@ static int macii_init_via(void)
/* Send an ADB poll (Talk Register 0 command prepended to the request queue) */
static void macii_queue_poll(void)
{
/* No point polling the active device as it will never assert SRQ, so
* poll the next device in the autopoll list. This could leave us
* stuck in a polling loop if an unprobed device is asserting SRQ.
* In theory, that could only happen if a device was plugged in after
* probing started. Unplugging it again will break the cycle.
* (Simply polling the next higher device often ends up polling almost
* every device (after wrapping around), which takes too long.)
*/
int device_mask;
int next_device;
static struct adb_request req;
unsigned char poll_command;
unsigned int poll_addr;
/* This only polls devices in the autopoll list, which assumes that
* unprobed devices never assert SRQ. That could happen if a device was
* plugged in after the adb bus scan. Unplugging it again will resolve
* the problem. This behaviour is similar to MacOS.
*/
if (!autopoll_devs)
return;
device_mask = (1 << (((command_byte & 0xF0) >> 4) + 1)) - 1;
if (autopoll_devs & ~device_mask)
next_device = ffs(autopoll_devs & ~device_mask) - 1;
else
next_device = ffs(autopoll_devs) - 1;
/* The device most recently polled may not be the best device to poll
* right now. Some other device(s) may have signalled SRQ (the active
* device won't do that). Or the autopoll list may have been changed.
* Try polling the next higher address.
*/
poll_addr = (last_poll_cmd & ADDR_MASK) >> 4;
if ((srq_asserted && last_cmd == last_poll_cmd) ||
!(autopoll_devs & (1 << poll_addr))) {
unsigned int higher_devs;
adb_request(&req, NULL, ADBREQ_NOSEND, 1, ADB_READREG(next_device, 0));
higher_devs = autopoll_devs & -(1 << (poll_addr + 1));
poll_addr = ffs(higher_devs ? higher_devs : autopoll_devs) - 1;
}
/* Send a Talk Register 0 command */
poll_command = ADB_READREG(poll_addr, 0);
/* No need to repeat this Talk command. The transceiver will do that
* as long as it is idle.
*/
if (poll_command == last_cmd)
return;
adb_request(&req, NULL, ADBREQ_NOSEND, 1, poll_command);
req.sent = 0;
req.complete = 0;
req.reply_len = 0;
req.next = current_req;
if (current_req != NULL) {
if (WARN_ON(current_req)) {
current_req = &req;
} else {
current_req = &req;
@ -266,37 +285,22 @@ static int macii_write(struct adb_request *req)
/* Start auto-polling */
static int macii_autopoll(int devs)
{
static struct adb_request req;
unsigned long flags;
int err = 0;
local_irq_save(flags);
/* bit 1 == device 1, and so on. */
autopoll_devs = devs & 0xFFFE;
if (autopoll_devs && !current_req) {
/* Send a Talk Reg 0. The controller will repeatedly transmit
* this as long as it is idle.
*/
adb_request(&req, NULL, ADBREQ_NOSEND, 1,
ADB_READREG(ffs(autopoll_devs) - 1, 0));
err = macii_write(&req);
if (!current_req) {
macii_queue_poll();
if (current_req && macii_state == idle)
macii_start();
}
local_irq_restore(flags);
return err;
}
static inline int need_autopoll(void)
{
/* Was the last command Talk Reg 0
* and is the target on the autopoll list?
*/
if ((command_byte & 0x0F) == 0x0C &&
((1 << ((command_byte & 0xF0) >> 4)) & autopoll_devs))
return 0;
return 1;
return 0;
}
/* Prod the chip without interrupts */
@ -333,7 +337,12 @@ static void macii_start(void)
*/
/* store command byte */
command_byte = req->data[1];
last_cmd = req->data[1];
/* If this is a Talk Register 0 command, store the command byte */
if ((last_cmd & CMD_MASK) == ADB_READREG(0, 0))
last_poll_cmd = last_cmd;
/* Output mode */
via[ACR] |= SR_OUT;
/* Load data */
@ -424,10 +433,11 @@ static irqreturn_t macii_interrupt(int irq, void *arg)
if (req->done)
(*req->done)(req);
if (current_req)
if (!current_req)
macii_queue_poll();
if (current_req && macii_state == idle)
macii_start();
else if (need_autopoll())
macii_autopoll(autopoll_devs);
}
if (macii_state == idle) {
@ -507,14 +517,11 @@ static irqreturn_t macii_interrupt(int irq, void *arg)
macii_state = idle;
/* SRQ seen before, initiate poll now */
if (srq_asserted)
if (!current_req)
macii_queue_poll();
if (current_req)
macii_start();
else if (need_autopoll())
macii_autopoll(autopoll_devs);
if (macii_state == idle)
via[B] = (via[B] & ~ST_MASK) | ST_IDLE;