[PATCH] arm64: use readq() instead of readl() to read 64bit entry_point

[lorenzo.pieralisi@arm.com (Lorenzo Pieralisi)]

On Mon, Jun 26, 2017 at 03:16:25PM +0200, Luc Van Oostenryck wrote:
> Here the entrypoint, declared as a 64 bit integer, is read from
> a pointer to 64bit integer but the read is done via readl_relaxed()
> which is for 32bit quantities.
> 
> All the high bits will thus be lost which change the meaning
> of the test against zero done later.
> 
> Fix this by using readq_relaxed() instead as it should be for
> 64bit quantities.
> 
> Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
> 
> ---
> 
> !!! Warning !!!
>    I don't have the HW to test this, nor have I read the ACPI specs.
>    This is only compile tested.
> ---
>  arch/arm64/kernel/acpi_parking_protocol.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Patch is correct but as Mark already mentioned I would like some testing
done on systems that rely on the parking protocol (hopefully FW clears
the entry point correctly but I want to understand if this patch would
trigger regressions that would force us to add quirks around it - even
if we know this patch does the right thing from a kernel perspective).

Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

> diff --git a/arch/arm64/kernel/acpi_parking_protocol.c b/arch/arm64/kernel/acpi_parking_protocol.c
> index 1f5655cd9..f35e80aad 100644
> --- a/arch/arm64/kernel/acpi_parking_protocol.c
> +++ b/arch/arm64/kernel/acpi_parking_protocol.c
> @@ -125,7 +125,7 @@ static void acpi_parking_protocol_cpu_postboot(void)
>  	struct parking_protocol_mailbox __iomem *mailbox = cpu_entry->mailbox;
>  	__le64 entry_point;
>  
> -	entry_point = readl_relaxed(&mailbox->entry_point);
> +	entry_point = readq_relaxed(&mailbox->entry_point);
>  	/*
>  	 * Check if firmware has cleared the entry_point as expected
>  	 * by the protocol specification.
> -- 
> 2.13.0
>