Re: [PATCH] PCI: dwc: Restore ATU memory resource setup to use last entry

[Vidya Sagar <vidyas@nvidia.com>]

On 10/26/2020 9:18 PM, Rob Herring wrote:
> External email: Use caution opening links or attachments
> 
> 
> Prior to commit 0f71c60ffd26 ("PCI: dwc: Remove storing of PCI
> resources"), the DWC driver was setting up the last memory resource
> rather than the first memory resource. This doesn't matter for most
> platforms which only have 1 memory resource, but it broke Tegra194 which
> has a 2nd (prefetchable) memory region which requires an ATU entry. The
> first region on Tegra194 relies on the default 1:1 pass-thru of outbound
> transactions which doesn't need an ATU entry.
> 
> Fixes: 0f71c60ffd26 ("PCI: dwc: Remove storing of PCI resources")
> Reported-by: Vidya Sagar <vidyas@nvidia.com>
> Cc: Jingoo Han <jingoohan1@gmail.com>
> Cc: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Signed-off-by: Rob Herring <robh@kernel.org>
> ---
>   drivers/pci/controller/dwc/pcie-designware-host.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 674f32db85ca..44c2a6572199 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -586,8 +586,12 @@ void dw_pcie_setup_rc(struct pcie_port *pp)
>           * ATU, so we should not program the ATU here.
>           */
>          if (pp->bridge->child_ops == &dw_child_pcie_ops) {
> -               struct resource_entry *entry =
> -                       resource_list_first_type(&pp->bridge->windows, IORESOURCE_MEM);
> +               struct resource_entry *tmp, *entry = NULL;
> +
> +               /* Get last memory resource entry */
> +               resource_list_for_each_entry(tmp, &pp->bridge->windows)
> +                       if (resource_type(tmp->res) == IORESOURCE_MEM)
> +                               entry = tmp;
This patch works for Tegra194 with its 'ranges' property in its current 
shape. But, this still doesn't work if ATU mapping needs to be set for 
both prefetchable and non-prefetchable regions. The series I pushed at 
http://patchwork.ozlabs.org/project/linux-pci/list/?series=209764 works 
for this condition as well.
When it comes to configuring the ATU to handle multiple memory apertures 
(which is the ultimate goal), I think we need to understand the side 
effects of removing I/O mapping in platforms where the number of view 
ports available are not enough to have I/O mapping.

> 
>                  dw_pcie_prog_outbound_atu(pci, PCIE_ATU_REGION_INDEX0,
>                                            PCIE_ATU_TYPE_MEM, entry->res->start,
> --
> 2.25.1
>