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firewire: fw-ohci: enforce read order for selfID generation

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It seems unlikely, but access to self_id_cpu[0] could at least in theory
be deferred until after the loop over self_id_cpu[1..n] or even after
the subsequent reg_read.  Enforce the desired order by a read barrier.

Also prevent the reg_read from being reordered relative to the for loop.
This isn't necessary if the loop's conditional printk counts as an
implicit barrier, but better make it explicit.

(self_id_cpu[] is a coherent DMA buffer.)

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
This commit is contained in:
Stefan Richter 2007-08-25 14:08:19 +02:00
parent df8ec2490f
commit ee71c2f9ee
1 changed files with 3 additions and 0 deletions
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3
drivers/firewire/fw-ohci.c
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@ -30,6 +30,7 @@
#include <asm/uaccess.h>
#include <asm/semaphore.h>
#include <asm/system.h>
#include "fw-transaction.h"
#include "fw-ohci.h"
@ -926,12 +927,14 @@ static void bus_reset_tasklet(unsigned long data)
self_id_count = (reg_read(ohci, OHCI1394_SelfIDCount) >> 3) & 0x3ff;
generation = (le32_to_cpu(ohci->self_id_cpu[0]) >> 16) & 0xff;
rmb();
for (i = 1, j = 0; j < self_id_count; i += 2, j++) {
if (ohci->self_id_cpu[i] != ~ohci->self_id_cpu[i + 1])
fw_error("inconsistent self IDs\n");
ohci->self_id_buffer[j] = le32_to_cpu(ohci->self_id_cpu[i]);
}
rmb();
/*
* Check the consistency of the self IDs we just read. The