Re: [[PATCH v1]] of/pci: fix a bug in function pci_pio_to_address

[Bjorn Helgaas <bhelgaas@google.com>]

On Wed, Apr 22, 2015 at 09:35:59PM +0800, Zhichang Yuan wrote:
> In the patch whose commit id is 41f8bba7f5552d0, function pci_pio_to_address
> was introduced to retieve the corresponding I/O port by CPU address. But the
> convertion processing is not correct. It will return a wrong I/O port.
> This patch will fix it.

Hmmm, this subject and changelog don't seem right.  41f8bba7f555 did add
pci_pio_to_address(), but that converts an I/O port to a CPU address, and
this patch doesn't touch that function.

This patch changes pci_address_to_pio(), which does return the I/O port
corresponding to a CPU physical address.  This function was modified (but
not added) by 41f8bba7f555.

Please add:

Fixes: 41f8bba7f555 ("of/pci: Add pci_register_io_range() and pci_pio_to_address()")
CC: stable@vger.kernel.org	# v3.18+

> Signed-off-by: Zhichang Yuan <yuanzhichang@hisilicon.com>
> ---
>  drivers/of/address.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/of/address.c b/drivers/of/address.c
> index 78a7dcb..6906a3f 100644
> --- a/drivers/of/address.c
> +++ b/drivers/of/address.c
> @@ -765,7 +765,7 @@ unsigned long __weak pci_address_to_pio(phys_addr_t address)
>  	spin_lock(&io_range_lock);
>  	list_for_each_entry(res, &io_range_list, list) {
>  		if (address >= res->start && address < res->start + res->size) {
> -			addr = res->start - address + offset;
> +			addr = address - res->start + offset;

This looks like it's been broken since v3.18, and it's used by many
platforms.  I/O port space isn't as common as it used to be, but it's still
surprising that nobody noticed until now.

This change does look correct to me, but I want to double-check that we're
actually going to *fix* a bunch of platforms rather than breaking them.

>  			break;
>  		}
>  		offset += res->size;
> -- 
> 1.9.1
>