This patch does following improvements to sbi_fifo:
1. Use valid SBI_Exxxx error codes instead of -1
2. The sbi_fifo_is_full() and sbi_fifo_is_empty() did
not acquire qlock before accessing head and tail
hence fixed it
3. Added avail member for ease in debugging and simplifying
head/tail updates.
Due to above changes size of sbi_fifo changes from 48 bytes
to 56 bytes.
Signed-off-by: Anup Patel <anup.patel@wdc.com>
Currently, there is no provision for tracking multiple IPIs sent
to a single hart at the same time by different harts.
Use a fifo manage the outstanding requests. While dequeueing, read all
the entries once, because we have only 1 bit to track the type of IPI.
Once the queue is full, busy wait until the there is space available in
queue. This is not the most elegant approach. It should be changed in
favor of a wakeup event once available in opensbi.
Signed-off-by: Atish Patra <atish.patra@wdc.com>
