powerpc/powernv: Flush console before platform error reboot

Unrecovered MCE and HMI errors are sent through a special restart OPAL
call to log the platform error. The downside is that they don't go
through normal Linux crash paths, so they don't give much information
to the Linux console.

Change this by providing a special crash function which does some of
the console flushing from the panic() path before calling firmware to
reboot.

The downside of this is a little more code to execute before reaching
the firmware reboot. However in practice, it's critical to get the
Linux console messages output in order to debug a problem. So this is
a desirable tradeoff.

Note on the implementation: It is difficult to plumb a custom reboot
handler into the panic path, because panic does a little bit too much
work. For example, it will try to delay with the timebase, but that
may be corrupted in some cases resulting in a hang without reaching
the platform reboot. Another problem is that panic can invoke the
crash dump code which is not what we want in the case of a hardware
platform error. Long-term the best solution will be to rework the
panic path so it can be suitable for this kind of panic, but for now
we just duplicate a bit of the code.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index 97ff192f5cfb..726c23304a57 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -50,7 +50,7 @@ int64_t opal_tpo_write(uint64_t token, uint32_t year_mon_day,
 		       uint32_t hour_min);
 int64_t opal_cec_power_down(uint64_t request);
 int64_t opal_cec_reboot(void);
-int64_t opal_cec_reboot2(uint32_t reboot_type, char *diag);
+int64_t opal_cec_reboot2(uint32_t reboot_type, const char *diag);
 int64_t opal_read_nvram(uint64_t buffer, uint64_t size, uint64_t offset);
 int64_t opal_write_nvram(uint64_t buffer, uint64_t size, uint64_t offset);
 int64_t opal_handle_interrupt(uint64_t isn, __be64 *outstanding_event_mask);