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powerpc/rtas: rtas_busy_delay_time() kernel-doc

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Provide API documentation for rtas_busy_delay_time(), explaining why we
return the same value for 9900 and -2.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211117060259.957178-3-nathanl@linux.ibm.com
This commit is contained in:
Nathan Lynch 2021-11-17 00:02:59 -06:00 committed by Michael Ellerman
parent 38f7b7067d
commit dd5cde457a
1 changed files with 19 additions and 2 deletions
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21
arch/powerpc/kernel/rtas.c
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@ -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)
{