| H A D | fsi-master-aspeed.c | 4134cb91 Mon Feb 22 22:17:37 CST 2021 Joel Stanley <joel@jms.id.au> fsi: aspeed: Emit fewer barriers in opb operations
When setting up a read or write to the OPB memory space, we must perform
five or six AHB writes. The ordering of these up until the trigger write
does not matter, so use writel_relaxed.
The generated code goes from (Debian GCC 10.2.1-6):
mov r8, r3
mcr 15, 0, sl, cr7, cr10, {4}
str sl, [r6, #20]
mcr 15, 0, sl, cr7, cr10, {4}
str r3, [r6, #24]
mcr 15, 0, sl, cr7, cr10, {4}
str r1, [r6, #28]
mcr 15, 0, sl, cr7, cr10, {4}
str r2, [r6, #32]
mcr 15, 0, sl, cr7, cr10, {4}
mov r1, #1
str r1, [r6, #64] ; 0x40
mcr 15, 0, sl, cr7, cr10, {4}
str r1, [r6, #4]
to this:
str r3, [r7, #20]
str r2, [r7, #24]
str r1, [r7, #28]
str r3, [r7, #64]
mov r8, #0
mcr 15, 0, r8, cr7, cr10, {4}
str r3, [r7, #4]
Signed-off-by: Joel Stanley <joel@jms.id.au>
Acked-by: Jeremy Kerr <jk@ozlabs.org>
Reviewed-by: Eddie James <eajames@linux.ibm.com>
Tested-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20210223041737.171274-1-joel@jms.id.au
Signed-off-by: Joel Stanley <joel@jms.id.au>
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