Re: [PATCH] PCI: dwc: Fix stop condition on __dw_pcie_ep_find_next_cap()

[Kishon Vijay Abraham I <kishon@ti.com>]

Hi Gustavo,

On 28/01/19 11:52 PM, Gustavo Pimentel wrote:
> The combination of __dw_pcie_ep_find_next_cap() and
> dw_pcie_ep_find_capability() allows to search on the Endpoint
> configuration space for a specific capability ID.
> 
> This search is done recursively by __dw_pcie_ep_find_next_cap() jumping
> from capability to capability (using the next offset register to calculate
> next jump address), stopping until the next offset register is null or
> the current capability meets the desired ID.
> 
> However, if the desired capability is at the end of that list, the
> recursive search will be returning because the next offset will
> be null (thus filling the first stop condition) and not because it
> has reached the desired ID and therefore reporting capability "not
> found".
> 
> This fix will swap the stop conditions order of
> __dw_pcie_ep_find_next_cap(), allowing to find the desired capability ID,
> if it encounters at the end of the list.
> 
> Fixes: beb4641a787d ("PCI: dwc: Add MSI-X callbacks handler")
> Reported-by: Jian Wang <jianwang@ra.rockwell.com>
> Signed-off-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Cc: Kishon Vijay Abraham I <kishon@ti.com>
> Cc: stable@vger.kernel.org

I had already posted a patch fixing it as part of my AM654 PCIe support series [1].

Thanks
Kishon
[1] -> https://lore.kernel.org/lkml/20190114132424.6445-19-kishon@ti.com/T/#u
> ---
>  drivers/pci/controller/dwc/pcie-designware-ep.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> index a543c45..0258894 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -50,12 +50,12 @@ static u8 __dw_pcie_ep_find_next_cap(struct dw_pcie *pci, u8 cap_ptr,
>  	next_cap_ptr = (reg & 0xff00) >> 8;
>  	cap_id = (reg & 0x00ff);
>  
> -	if (!next_cap_ptr || cap_id > PCI_CAP_ID_MAX)
> -		return 0;
> -
>  	if (cap_id == cap)
>  		return cap_ptr;
>  
> +	if (!next_cap_ptr || cap_id > PCI_CAP_ID_MAX)
> +		return 0;
> +
>  	return __dw_pcie_ep_find_next_cap(pci, next_cap_ptr, cap);
>  }
>  
>