[PATCH 2/2] powerpc/powernv: Skip registering log region when CONFIG_PRINTK=n

[Stewart Smith]

Pranith Kumar <bobby.prani at gmail.com> writes:
> When CONFIG_PRINTK=n, log_buf_addr_get() returns NULL and log_buf_len_get()
> return 0. Check for these return values and skip registering the dump buffer.
>
> Signed-off-by: Pranith Kumar <bobby.prani at gmail.com>
> CC: Michael Ellerman <mpe at ellerman.id.au>

(investigating what would occur on systems with current firmware..)

Looking at hw/fsp/fsp-mdst-table.c in skiboot it appears that we'd end
up logging an error log about being passed the size 0 and return
OPAL_PARAMETER back to Linux.

While harmless, this is, naturally, not awesome to log an error about
being unable to grab kernel log on crash every time you boot.

Reviewed-by: Stewart Smith <stewart at linux.vnet.ibm.com>

> ---
>  arch/powerpc/platforms/powernv/opal.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
> index f10b9ec..1db119f0 100644
> --- a/arch/powerpc/platforms/powernv/opal.c
> +++ b/arch/powerpc/platforms/powernv/opal.c
> @@ -667,7 +667,13 @@ static void __init opal_dump_region_init(void)
>  
>  	/* Register kernel log buffer */
>  	addr = log_buf_addr_get();
> +	if (addr == NULL)
> +		return;
> +
>  	size = log_buf_len_get();
> +	if (size == 0)
> +		return;
> +
>  	rc = opal_register_dump_region(OPAL_DUMP_REGION_LOG_BUF,
>  				       __pa(addr), size);
>  	/* Don't warn if this is just an older OPAL that doesn't
> -- 
> 1.9.1
>
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