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Subject[PATCH 02/15] powerpc/powernv: Fix OPAL console driver OPAL_BUSY loops
Date
The OPAL console driver does not delay in case it gets OPAL_BUSY or
OPAL_BUSY_EVENT from firmware.

It can't yet be made to sleep because it is called under spinlock,
but it can be changed to the standard OPAL_BUSY loop form, and a
delay added to keep it from hitting the firmware too frequently.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
arch/powerpc/platforms/powernv/opal.c | 38 ++++++++++++++++-----------
1 file changed, 23 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index e695b836fd49..6b621d47ac29 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -378,33 +378,41 @@ int opal_put_chars(uint32_t vtermno, const char *data, int total_len)
/* We still try to handle partial completions, though they
* should no longer happen.
*/
- rc = OPAL_BUSY;
- while(total_len > 0 && (rc == OPAL_BUSY ||
- rc == OPAL_BUSY_EVENT || rc == OPAL_SUCCESS)) {
+
+ while (total_len > 0) {
olen = cpu_to_be64(total_len);
- rc = opal_console_write(vtermno, &olen, data);
+
+ rc = OPAL_BUSY;
+ while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
+ rc = opal_console_write(vtermno, &olen, data);
+ if (rc == OPAL_BUSY_EVENT) {
+ mdelay(OPAL_BUSY_DELAY_MS);
+ opal_poll_events(NULL);
+ } else if (rc == OPAL_BUSY) {
+ mdelay(OPAL_BUSY_DELAY_MS);
+ }
+ }
+
len = be64_to_cpu(olen);

/* Closed or other error drop */
- if (rc != OPAL_SUCCESS && rc != OPAL_BUSY &&
- rc != OPAL_BUSY_EVENT) {
- written += total_len;
+ if (rc != OPAL_SUCCESS) {
+ written += total_len; /* drop remaining chars */
break;
}
- if (rc == OPAL_SUCCESS) {
- total_len -= len;
- data += len;
- written += len;
- }
+
+ total_len -= len;
+ data += len;
+ written += len;
+
/* This is a bit nasty but we need that for the console to
* flush when there aren't any interrupts. We will clean
* things a bit later to limit that to synchronous path
* such as the kernel console and xmon/udbg
*/
- do
+ do {
opal_poll_events(&evt);
- while(rc == OPAL_SUCCESS &&
- (be64_to_cpu(evt) & OPAL_EVENT_CONSOLE_OUTPUT));
+ } while (be64_to_cpu(evt) & OPAL_EVENT_CONSOLE_OUTPUT);
}
spin_unlock_irqrestore(&opal_write_lock, flags);
return written;
--
2.17.0
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