Subject: Re: [PATCH v6 10/42] powerpc/powernv: pnv_ioda_setup_dma() configure one PE only

From: Alexey Kardashevskiy <[email-masked]>
Date: Mon, 10 Aug 2015 19:31:11 +1000

On 08/06/2015 02:11 PM, Gavin Shan wrote:
> The original implementation of pnv_ioda_setup_dma() iterates the
> list of PEs and configures the DMA32 space for them one by one.
> The function was designed to be called during PHB fixup time.
> When configuring PE's DMA32 space in pcibios_setup_bridge(), in
> order to support PCI hotplug, we have to have the function PE
> oriented.
>
> This renames pnv_ioda_setup_dma() to pnv_ioda1_setup_dma() and
> adds one more argument "struct pnv_ioda_pe *pe" to it. The caller,
> pnv_pci_ioda_setup_DMA(), gets PE from the list and passes to it
> or pnv_pci_ioda2_setup_dma_pe(). The patch shouldn't cause behavioral
> changes.
>
> Signed-off-by: Gavin Shan <[email-masked]>
> ---
>   arch/powerpc/platforms/powernv/pci-ioda.c | 75 +++++++++++++++----------------
>   1 file changed, 36 insertions(+), 39 deletions(-)
>
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index 8456f37..cd22002 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -2443,52 +2443,29 @@ static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
>   		pnv_ioda_setup_bus_dma(pe, pe->pbus);
>   }
>
> -static void pnv_ioda_setup_dma(struct pnv_phb *phb)
> +static unsigned int pnv_ioda1_setup_dma(struct pnv_phb *phb,
> +					struct pnv_ioda_pe *pe,
> +					unsigned int base)
>   {
>   	struct pci_controller *hose = phb->hose;
> -	struct pnv_ioda_pe *pe;
> -	unsigned int dma_weight;
> +	unsigned int dma_weight, segs;
>
>   	/* Calculate the PHB's DMA weight */
>   	dma_weight = pnv_ioda_phb_dma_weight(phb);
>   	pr_info("PCI%04x has %ld DMA32 segments, total weight %d\n",
>   		hose->global_number, phb->ioda.dma32_segcount, dma_weight);
>
> -	pnv_pci_ioda_setup_opal_tce_kill(phb);
> -
> -	/* Walk our PE list and configure their DMA segments, hand them
> -	 * out one base segment plus any residual segments based on
> -	 * weight
> -	 */
> -	list_for_each_entry(pe, &phb->ioda.pe_dma_list, dma_link) {
> -		if (!pe->dma32_weight)
> -			continue;
> -
> -		/*
> -		 * For IODA2 compliant PHB3, we needn't care about the weight.
> -		 * The all available 32-bits DMA space will be assigned to
> -		 * the specific PE.
> -		 */
> -		if (phb->type == PNV_PHB_IODA1) {
> -			unsigned int segs, base = 0;
> -
> -			if (pe->dma32_weight <
> -			    dma_weight / phb->ioda.dma32_segcount)
> -				segs = 1;
> -			else
> -				segs = (pe->dma32_weight *
> -					phb->ioda.dma32_segcount) / dma_weight;
> -
> -			pe_info(pe, "DMA32 weight %d, assigned %d segments\n",
> -				pe->dma32_weight, segs);
> -			pnv_pci_ioda_setup_dma_pe(phb, pe, base, segs);
> +	if (pe->dma32_weight <
> +	    dma_weight / phb->ioda.dma32_segcount)

Can be one line now.

> +		segs = 1;
> +	else
> +		segs = (pe->dma32_weight *
> +			phb->ioda.dma32_segcount) / dma_weight;
> +	pe_info(pe, "DMA weight %d, assigned %d segments\n",
> +		pe->dma32_weight, segs);
> +	pnv_pci_ioda_setup_dma_pe(phb, pe, base, segs);

Why not to merge pnv_ioda1_setup_dma() to pnv_pci_ioda_setup_dma_pe()?

>
> -			base += segs;
> -		} else {
> -			pe_info(pe, "Assign DMA32 space\n");
> -			pnv_pci_ioda2_setup_dma_pe(phb, pe);
> -		}
> -	}
> +	return segs;
>   }
>
>   #ifdef CONFIG_PCI_MSI
> @@ -2955,12 +2932,32 @@ static void pnv_pci_ioda_setup_DMA(void)
>   {
>   	struct pci_controller *hose, *tmp;
>   	struct pnv_phb *phb;
> +	struct pnv_ioda_pe *pe;
> +	unsigned int base;
>
>   	list_for_each_entry_safe(hose, tmp, &hose_list, list_node) {
> -		pnv_ioda_setup_dma(hose->private_data);
> +		phb = hose->private_data;
> +		pnv_pci_ioda_setup_opal_tce_kill(phb);
> +
> +		base = 0;
> +		list_for_each_entry(pe, &phb->ioda.pe_dma_list, dma_link) {
> +			if (!pe->dma32_weight)
> +				continue;
> +
> +			switch (phb->type) {
> +			case PNV_PHB_IODA1:
> +				base += pnv_ioda1_setup_dma(phb, pe, base);

This @base handling seems never be tested between 8..11 as "[PATCH v6 
11/42] powerpc/powernv: Trace DMA32 segments consumed by PE"
removes it and I suspect you only tested the final version. Which is ok for 
the final result but not ok for bisectability.

Looks like 8/42, 9/42, 10/42, 11/42 need to be rearranged or merged to 
remove this multiple @base touching.

> +				break;
> +			case PNV_PHB_IODA2:
> +				pnv_pci_ioda2_setup_dma_pe(phb, pe);
> +				break;
> +			default:
> +				pr_warn("%s: No DMA for PHB type %d\n",
> +					__func__, phb->type);
> +			}
> +		}
>
>   		/* Mark the PHB initialization done */
> -		phb = hose->private_data;
>   		phb->initialized = 1;
>   	}
>   }
>

-- 
Alexey