On Mon, 2008-12-01 at 19:17 +0800, Matthew Garrett wrote:
> The ACPI specification says that we should use the 64-bit address offsets
> contained within the FADT if they exist. However, Windows uses the legacy
> address.
Including vista?
thanks,
rui
> Various vendors have left incorrect values in the 64-bit field
> which then causes problems later. Since the vast majority of machines have
> never been tested with an OS that uses the 64-bit value by default, we should
> behave like Windows and ignore the spec by only using the 64-bit address if
> it contains something that can't be represented in the legacy field. Since
> system io space is only 16 bits on x86, this should be entirely safe.
>
> Signed-off-by: Matthew Garrett <mjg@xxxxxxxxxx>
>
> ---
>
> Len, this is a clear case of the spec not matching real-life behaviour.
> I'd be amazed if anyone can find an x86 system that uses system-io space
> for these values and doesn't contain an accurate value in the 32-bit
> field. On the other hand, we've seen machines that assume the
> Windows-style behaviour and we keep finding more. A blacklist isn't the
> correct solution for this problem.
>
> diff --git a/drivers/acpi/tables/tbfadt.c b/drivers/acpi/tables/tbfadt.c
> index 2817158..89a3c82 100644
> --- a/drivers/acpi/tables/tbfadt.c
> +++ b/drivers/acpi/tables/tbfadt.c
> @@ -320,9 +320,30 @@ static void acpi_tb_convert_fadt(void)
> ACPI_ADD_PTR(struct acpi_generic_address, &acpi_gbl_FADT,
> fadt_info_table[i].target);
>
> - /* Expand only if the X target is null */
> -
> - if (!target->address) {
> + /*
> + * The ACPI specification says that we should use the
> + * 64-bit address offsets if they exists. However,
> + * Windows uses the legacy address. Various vendors
> + * have left incorrect values in the 64-bit field,
> + * which then causes problems later. Since the vast
> + * majority of machines have never been tested with an
> + * OS that uses the 64-bit value by default, we should
> + * behave like Windows and ignore the spec by only
> + * using the 64-bit address if it contains something
> + * that can't be represented in the legacy
> + * field. Since system io space is only 16 bits on
> + * x86, this should be entirely safe. We also extend
> + * the 32-bit value into the 64-bit one if no 64-bit
> + * address is provided.
> + */
> +
> + if (!target->address
> +#ifdef CONFIG_X86
> + || (target->space_id == ACPI_ADR_SPACE_SYSTEM_IO &&
> + *ACPI_ADD_PTR(u32, &acpi_gbl_FADT,
> + fadt_info_table[i].source))
> +#endif
> + ) {
> acpi_tb_init_generic_address(target,
> *ACPI_ADD_PTR(u8,
> &acpi_gbl_FADT,
>
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