Re: [PATCH v4 6/7] PCI: keystone: Specify correct alignment requirement

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Fri, Jan 31, 2025 at 07:29:55PM +0100, Niklas Cassel wrote:
> The support for a specific iATU alignment was added in
> commit 2a9a801620ef ("PCI: endpoint: Add support to specify alignment for
> buffers allocated to BARs").
> 
> This commit specifically mentions both that the alignment by each DWC
> based EP driver should match CX_ATU_MIN_REGION_SIZE, and that AM65x
> specifically has a 64 KB alignment.
> 
> This also matches the CX_ATU_MIN_REGION_SIZE value specified by
> "12.2.2.4.7 PCIe Subsystem Address Translation" in the AM65x TRM:
> https://www.ti.com/lit/ug/spruid7e/spruid7e.pdf
> 
> This higher value, 1 MB, was obviously an ugly hack used to be able to
> handle Resizable BARs which have a minimum size of 1 MB.
> 
> Now when we actually have support for Resizable BARs, let's configure the
> iATU alignment requirement to the actual requirement.
> (BARs described as Resizable will still get aligned to 1 MB.)
> 
> Cc: stable+noautosel@kernel.org # Depends on PCI endpoint Resizable BARs series
> Fixes: 23284ad677a9 ("PCI: keystone: Add support for PCIe EP in AM654x Platforms")
> Signed-off-by: Niklas Cassel <cassel@kernel.org>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

- Mani

> ---
>  drivers/pci/controller/dwc/pci-keystone.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-keystone.c b/drivers/pci/controller/dwc/pci-keystone.c
> index fdc610ec7e5e..76a37368ae4f 100644
> --- a/drivers/pci/controller/dwc/pci-keystone.c
> +++ b/drivers/pci/controller/dwc/pci-keystone.c
> @@ -970,7 +970,7 @@ static const struct pci_epc_features ks_pcie_am654_epc_features = {
>  	.bar[BAR_3] = { .type = BAR_FIXED, .fixed_size = SZ_64K, },
>  	.bar[BAR_4] = { .type = BAR_FIXED, .fixed_size = 256, },
>  	.bar[BAR_5] = { .type = BAR_RESIZABLE, },
> -	.align = SZ_1M,
> +	.align = SZ_64K,
>  };
>  
>  static const struct pci_epc_features*
> -- 
> 2.48.1
> 

-- 
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