Subject: Re: [PATCH kernel 2/2] powerpc/powernv: Define PHB4 type and enable sketchy bypass on POWER9

From: Benjamin Herrenschmidt <[email-masked]>
Date: Sat, 16 Jun 2018 11:05:19 +1000

On Fri, 2018-06-01 at 18:10 +1000, Alexey Kardashevskiy wrote:
> These are found in POWER9 chips. Right now these PHBs have unknown type
> so changing it to PHB4 won't make much of a difference except enabling
> sketchy bypass for POWER9 as this does below.

And that will break on multi-chip systems since P9 doesn't have the
memory contiguous (it has the chip ID in the top bits).

Russell is working on a different implementation that should be much
more imune to the system physical memory layout.

> Signed-off-by: Alexey Kardashevskiy <[email-masked]>
> ---
>  arch/powerpc/platforms/powernv/pci.h      | 1 +
>  arch/powerpc/platforms/powernv/pci-ioda.c | 5 ++++-
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/pci.h b/arch/powerpc/platforms/powernv/pci.h
> index eada4b6..1408247 100644
> --- a/arch/powerpc/platforms/powernv/pci.h
> +++ b/arch/powerpc/platforms/powernv/pci.h
> @@ -23,6 +23,7 @@ enum pnv_phb_model {
>  	PNV_PHB_MODEL_UNKNOWN,
>  	PNV_PHB_MODEL_P7IOC,
>  	PNV_PHB_MODEL_PHB3,
> +	PNV_PHB_MODEL_PHB4,
>  	PNV_PHB_MODEL_NPU,
>  	PNV_PHB_MODEL_NPU2,
>  };
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index 9239142..66c2804 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -1882,7 +1882,8 @@ static int pnv_pci_ioda_dma_set_mask(struct pci_dev *pdev, u64 dma_mask)
>  		if (dma_mask >> 32 &&
>  		    dma_mask > (memory_hotplug_max() + (1ULL << 32)) &&
>  		    pnv_pci_ioda_pe_single_vendor(pe) &&
> -		    phb->model == PNV_PHB_MODEL_PHB3) {
> +		    (phb->model == PNV_PHB_MODEL_PHB3 ||
> +		     phb->model == PNV_PHB_MODEL_PHB4)) {
>  			/* Configure the bypass mode */
>  			rc = pnv_pci_ioda_dma_64bit_bypass(pe);
>  			if (rc)
> @@ -3930,6 +3931,8 @@ static void __init pnv_pci_init_ioda_phb(struct device_node *np,
>  		phb->model = PNV_PHB_MODEL_P7IOC;
>  	else if (of_device_is_compatible(np, "ibm,power8-pciex"))
>  		phb->model = PNV_PHB_MODEL_PHB3;
> +	else if (of_device_is_compatible(np, "ibm,power9-pciex"))
> +		phb->model = PNV_PHB_MODEL_PHB4;
>  	else if (of_device_is_compatible(np, "ibm,power8-npu-pciex"))
>  		phb->model = PNV_PHB_MODEL_NPU;
>  	else if (of_device_is_compatible(np, "ibm,power9-npu-pciex"))