• Stewart Smith's avatar
    powerpc/powernv: Read OPAL error log and export it through sysfs · 774fea1a
    Stewart Smith authored
    Based on a patch by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
    
    This patch adds support to read error logs from OPAL and export
    them to userspace through a sysfs interface.
    
    We export each log entry as a directory in /sys/firmware/opal/elog/
    
    Currently, OPAL will buffer up to 128 error log records, we don't
    need to have any knowledge of this limit on the Linux side as that
    is actually largely transparent to us.
    
    Each error log entry has the following files: id, type, acknowledge, raw.
    Currently we just export the raw binary error log in the 'raw' attribute.
    In a future patch, we may parse more of the error log to make it a bit
    easier for userspace (e.g. to be able to display a brief summary in
    petitboot without having to have a full parser).
    
    If we have >128 logs from OPAL, we'll only be notified of 128 until
    userspace starts acknowledging them. This limitation may be lifted in
    the future and with this patch, that should "just work" from the linux side.
    
    A userspace daemon should:
    - wait for error log entries using normal mechanisms (we announce creation)
    - read error log entry
    - save error log entry safely to disk
    - acknowledge the error log entry
    - rinse, repeat.
    
    On the Linux side, we read the error log when we're notified of it. This
    possibly isn't ideal as it would be better to only read them on-demand.
    However, this doesn't really work with current OPAL interface, so we
    read the error log immediately when notified at the moment.
    
    I've tested this pretty extensively and am rather confident that the
    linux side of things works rather well. There is currently an issue with
    the service processor side of things for >128 error logs though.
    Signed-off-by: default avatarStewart Smith <stewart@linux.vnet.ibm.com>
    Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
    774fea1a
opal-elog.c 6.85 KB