diff options
Diffstat (limited to 'arch/powerpc/kernel/rtas.c')
| -rw-r--r-- | arch/powerpc/kernel/rtas.c | 104 |
1 files changed, 91 insertions, 13 deletions
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c index ff80bbad22a5..733e6ef36758 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c @@ -492,8 +492,25 @@ int rtas_call(int token, int nargs, int nret, int *outputs, ...) } EXPORT_SYMBOL(rtas_call); -/* For RTAS_BUSY (-2), delay for 1 millisecond. For an extended busy status - * code of 990n, perform the hinted delay of 10^n (last digit) milliseconds. +/** + * rtas_busy_delay_time() - From an RTAS status value, calculate the + * suggested delay time in milliseconds. + * + * @status: a value returned from rtas_call() or similar APIs which return + * the status of a RTAS function call. + * + * Context: Any context. + * + * Return: + * * 100000 - If @status is 9905. + * * 10000 - If @status is 9904. + * * 1000 - If @status is 9903. + * * 100 - If @status is 9902. + * * 10 - If @status is 9901. + * * 1 - If @status is either 9900 or -2. This is "wrong" for -2, but + * some callers depend on this behavior, and the worst outcome + * is that they will delay for longer than necessary. + * * 0 - If @status is not a busy or extended delay value. */ unsigned int rtas_busy_delay_time(int status) { @@ -513,17 +530,77 @@ unsigned int rtas_busy_delay_time(int status) } EXPORT_SYMBOL(rtas_busy_delay_time); -/* For an RTAS busy status code, perform the hinted delay. */ -unsigned int rtas_busy_delay(int status) +/** + * rtas_busy_delay() - helper for RTAS busy and extended delay statuses + * + * @status: a value returned from rtas_call() or similar APIs which return + * the status of a RTAS function call. + * + * Context: Process context. May sleep or schedule. + * + * Return: + * * true - @status is RTAS_BUSY or an extended delay hint. The + * caller may assume that the CPU has been yielded if necessary, + * and that an appropriate delay for @status has elapsed. + * Generally the caller should reattempt the RTAS call which + * yielded @status. + * + * * false - @status is not @RTAS_BUSY nor an extended delay hint. The + * caller is responsible for handling @status. + */ +bool rtas_busy_delay(int status) { unsigned int ms; + bool ret; - might_sleep(); - ms = rtas_busy_delay_time(status); - if (ms && need_resched()) - msleep(ms); + switch (status) { + case RTAS_EXTENDED_DELAY_MIN...RTAS_EXTENDED_DELAY_MAX: + ret = true; + ms = rtas_busy_delay_time(status); + /* + * The extended delay hint can be as high as 100 seconds. + * Surely any function returning such a status is either + * buggy or isn't going to be significantly slowed by us + * polling at 1HZ. Clamp the sleep time to one second. + */ + ms = clamp(ms, 1U, 1000U); + /* + * The delay hint is an order-of-magnitude suggestion, not + * a minimum. It is fine, possibly even advantageous, for + * us to pause for less time than hinted. For small values, + * use usleep_range() to ensure we don't sleep much longer + * than actually needed. + * + * See Documentation/timers/timers-howto.rst for + * explanation of the threshold used here. In effect we use + * usleep_range() for 9900 and 9901, msleep() for + * 9902-9905. + */ + if (ms <= 20) + usleep_range(ms * 100, ms * 1000); + else + msleep(ms); + break; + case RTAS_BUSY: + ret = true; + /* + * We should call again immediately if there's no other + * work to do. + */ + cond_resched(); + break; + default: + ret = false; + /* + * Not a busy or extended delay status; the caller should + * handle @status itself. Ensure we warn on misuses in + * atomic context regardless. + */ + might_sleep(); + break; + } - return ms; + return ret; } EXPORT_SYMBOL(rtas_busy_delay); @@ -809,13 +886,13 @@ void rtas_os_term(char *str) /** * rtas_activate_firmware() - Activate a new version of firmware. * + * Context: This function may sleep. + * * Activate a new version of partition firmware. The OS must call this * after resuming from a partition hibernation or migration in order * to maintain the ability to perform live firmware updates. It's not * catastrophic for this method to be absent or to fail; just log the * condition in that case. - * - * Context: This function may sleep. */ void rtas_activate_firmware(void) { @@ -890,11 +967,12 @@ int rtas_call_reentrant(int token, int nargs, int nret, int *outputs, ...) #endif /* CONFIG_PPC_PSERIES */ /** - * Find a specific pseries error log in an RTAS extended event log. + * get_pseries_errorlog() - Find a specific pseries error log in an RTAS + * extended event log. * @log: RTAS error/event log * @section_id: two character section identifier * - * Returns a pointer to the specified errorlog or NULL if not found. + * Return: A pointer to the specified errorlog or NULL if not found. */ struct pseries_errorlog *get_pseries_errorlog(struct rtas_error_log *log, uint16_t section_id) |