Re: [PATCH v5 1/3] PCI: dwc: Fix msg_atu_index assignment

[Damien Le Moal <dlemoal@kernel.org>]

On 1/28/26 12:10 AM, Niklas Cassel wrote:
> When dw_pcie_iatu_setup() configures outbound address translation for both
> type PCIE_ATU_TYPE_MEM and PCIE_ATU_TYPE_IO, the iATU index to use is
> incremented before calling dw_pcie_prog_outbound_atu().
> 
> However, for msg_atu_index the index is not incremented before use,
> causing the iATU index to be the same as the last configured iATU index,
> which means that it will incorrectly use the same iATU index that is
> already in use, breaking outbound address translation.
> 
> In total there are three problems with this code:
> -It assigns msg_atu_index the same index that was used for the last
>  outbound address translation window, rather than incrementing the index
>  before assignment.
> -The index should only be incremented (and msg_atu_index assigned) if the
>  use_atu_msg feature is actually requested/in use (pp->use_atu_msg is set).
> -If the use_atu_msg feature is requested/in use, and there are no outbound
>  iATUs available, the code should return an error, as otherwise when this
>  this feature is used, it will use an iATU index that is out of bounds.
> 
> Fixes: e1a4ec1a9520 ("PCI: dwc: Add generic MSG TLP support for sending PME_Turn_Off when system suspend")
> Cc: stable@vger.kernel.org
> Reviewed-by: Frank Li <Frank.Li@nxp.com>
> Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
> Signed-off-by: Niklas Cassel <cassel@kernel.org>
> ---
>  drivers/pci/controller/dwc/pcie-designware-host.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index b3d6a474fd16..d7f57d77bdf5 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -982,7 +982,14 @@ static int dw_pcie_iatu_setup(struct dw_pcie_rp *pp)
>  		dev_warn(pci->dev, "Ranges exceed outbound iATU size (%d)\n",
>  			 pci->num_ob_windows);
>  
> -	pp->msg_atu_index = i;
> +	if (pp->use_atu_msg) {
> +		if (pci->num_ob_windows > ++i) {

I would still prefer:

		i++;
		if (pci->num_ob_windows > i) {

As that is far easier to understand rather than having to remember the value
return vs increment order for ++ as a prefix or suffix.
But not going to fight it.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>

> +			pp->msg_atu_index = i;
> +		} else {
> +			dev_err(pci->dev, "Cannot add outbound window for MSG TLP\n");
> +			return -ENOMEM;
> +		}
> +	}
>  
>  	i = 0;
>  	resource_list_for_each_entry(entry, &pp->bridge->dma_ranges) {


-- 
Damien Le Moal
Western Digital Research