Subject: Re: [PATCH v8 17/45] powerpc/powernv/ioda1: Improve DMA32 segment track

From: Alexey Kardashevskiy <[email-masked]>
Date: Tue, 19 Apr 2016 11:50:10 +1000

On 02/17/2016 02:44 PM, Gavin Shan wrote:
> In current implementation, the DMA32 segments required by one specific
> PE isn't calculated with the information hold in the PE independently.
> It conflicts with the PCI hotplug design: PE centralized, meaning the
> PE's DMA32 segments should be calculated from the information hold in
> the PE independently.
>
> This introduces an array (@dma32_segmap) for every PHB to track the
> DMA32 segmeng usage. Besides, this moves the logic calculating PE's
> consumed DMA32 segments to pnv_pci_ioda1_setup_dma_pe() so that PE's
> DMA32 segments are calculated/allocated from the information hold in
> the PE (DMA32 weight). Also the logic is improved: we try to allocate
> as much DMA32 segments as we can. It's acceptable that number of DMA32
> segments less than the expected number are allocated.
>
> Signed-off-by: Gavin Shan <[email-masked]>

This DMA segments business was the reason why I have not even tried 
implementing DDW for POWER7 - it is way too different from POWER8 and there 
is no chance that anyone outside Ozlabs will ever try using this in 
practice; the same applies to PCI hotplug on POWER7.

I am suggesting to ditch all IODA1 changes from this patchset as this code 
will hang around (unused) for may be a year or so and then will be gone as 
p5ioc2.

> ---
>   arch/powerpc/platforms/powernv/pci-ioda.c | 111 +++++++++++++++++-------------
>   arch/powerpc/platforms/powernv/pci.h      |   7 +-
>   2 files changed, 66 insertions(+), 52 deletions(-)
>
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index 0fc2309..59782fba 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -2007,20 +2007,54 @@ static unsigned int pnv_pci_ioda_total_dma_weight(struct pnv_phb *phb)
>   }
>
>   static void pnv_pci_ioda1_setup_dma_pe(struct pnv_phb *phb,
> -				       struct pnv_ioda_pe *pe,
> -				       unsigned int base,
> -				       unsigned int segs)
> +				       struct pnv_ioda_pe *pe)
>   {
>
>   	struct page *tce_mem = NULL;
>   	struct iommu_table *tbl;
> -	unsigned int tce32_segsz, i;
> +	unsigned int weight, total_weight;
> +	unsigned int tce32_segsz, base, segs, i;
>   	int64_t rc;
>   	void *addr;
>
>   	/* XXX FIXME: Handle 64-bit only DMA devices */
>   	/* XXX FIXME: Provide 64-bit DMA facilities & non-4K TCE tables etc.. */
>   	/* XXX FIXME: Allocate multi-level tables on PHB3 */
> +	total_weight = pnv_pci_ioda_total_dma_weight(phb);
> +	weight = pnv_pci_ioda_pe_dma_weight(pe);
> +
> +	segs = (weight * phb->ioda.dma32_count) / total_weight;
> +	if (!segs)
> +		segs = 1;
> +
> +	/*
> +	 * Allocate contiguous DMA32 segments. We begin with the expected
> +	 * number of segments. With one more attempt, the number of DMA32
> +	 * segments to be allocated is decreased by one until one segment
> +	 * is allocated successfully.
> +	 */
> +	while (segs) {
> +		for (base = 0; base <= phb->ioda.dma32_count - segs; base++) {
> +			for (i = base; i < base + segs; i++) {
> +				if (phb->ioda.dma32_segmap[i] !=
> +				    IODA_INVALID_PE)
> +					break;
> +			}
> +
> +			if (i >= base + segs)
> +				break;
> +		}
> +
> +		if (i >= base + segs)
> +			break;
> +
> +		segs--;
> +	}
> +
> +	if (!segs) {
> +		pe_warn(pe, "No available DMA32 segments\n");
> +		return;
> +	}
>
>   	tbl = pnv_pci_table_alloc(phb->hose->node);
>   	iommu_register_group(&pe->table_group, phb->hose->global_number,
> @@ -2028,6 +2062,8 @@ static void pnv_pci_ioda1_setup_dma_pe(struct pnv_phb *phb,
>   	pnv_pci_link_table_and_group(phb->hose->node, 0, tbl, &pe->table_group);
>
>   	/* Grab a 32-bit TCE table */
> +	pe_info(pe, "DMA weight %d (%d), assigned (%d) %d DMA32 segments\n",
> +		weight, total_weight, base, segs);
>   	pe_info(pe, " Setting up 32-bit TCE table at %08x..%08x\n",
>   		base * PNV_IODA1_DMA32_SEGSIZE,
>   		(base + segs) * PNV_IODA1_DMA32_SEGSIZE - 1);
> @@ -2064,6 +2100,10 @@ static void pnv_pci_ioda1_setup_dma_pe(struct pnv_phb *phb,
>   		}
>   	}
>
> +	/* Setup DMA32 segment mapping */
> +	for (i = base; i < base + segs; i++)
> +		phb->ioda.dma32_segmap[i] = pe->pe_number;
> +
>   	/* Setup linux iommu table */
>   	pnv_pci_setup_iommu_table(tbl, addr, tce32_segsz * segs,
>   				  base * PNV_IODA1_DMA32_SEGSIZE,
> @@ -2538,70 +2578,34 @@ static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb,
>   static void pnv_ioda_setup_dma(struct pnv_phb *phb)
>   {
>   	struct pci_controller *hose = phb->hose;
> -	unsigned int weight, total_weight, dma_pe_count;
> -	unsigned int residual, remaining, segs, base;
>   	struct pnv_ioda_pe *pe;
> -
> -	total_weight = pnv_pci_ioda_total_dma_weight(phb);
> -	dma_pe_count = 0;
> -	list_for_each_entry(pe, &phb->ioda.pe_list, list) {
> -		weight = pnv_pci_ioda_pe_dma_weight(pe);
> -		if (weight > 0)
> -			dma_pe_count++;
> -	}
> +	unsigned int weight;
>
>   	/* If we have more PE# than segments available, hand out one
>   	 * per PE until we run out and let the rest fail. If not,
>   	 * then we assign at least one segment per PE, plus more based
>   	 * on the amount of devices under that PE
>   	 */
> -	if (dma_pe_count > phb->ioda.tce32_count)
> -		residual = 0;
> -	else
> -		residual = phb->ioda.tce32_count - dma_pe_count;
> -
>   	pr_info("PCI: Domain %04x has %ld available 32-bit DMA segments\n",
> -		hose->global_number, phb->ioda.tce32_count);
> -	pr_info("PCI: %d PE# for a total weight of %d\n",
> -		dma_pe_count, total_weight);
> +		hose->global_number, phb->ioda.dma32_count);
>
>   	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
> -	 */
> -	remaining = phb->ioda.tce32_count;
> -	base = 0;
> +	/* Walk our PE list and configure their DMA segments */
>   	list_for_each_entry(pe, &phb->ioda.pe_list, list) {
>   		weight = pnv_pci_ioda_pe_dma_weight(pe);
>   		if (!weight)
>   			continue;
>
> -		if (!remaining) {
> -			pe_warn(pe, "No DMA32 resources available\n");
> -			continue;
> -		}
> -		segs = 1;
> -		if (residual) {
> -			segs += ((weight * residual) + (total_weight / 2)) /
> -				total_weight;
> -			if (segs > remaining)
> -				segs = remaining;
> -		}
> -
>   		/*
>   		 * 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) {
> -			pe_info(pe, "DMA weight %d, assigned %d DMA32 segments\n",
> -				weight, segs);
> -			pnv_pci_ioda1_setup_dma_pe(phb, pe, base, segs);
> +			pnv_pci_ioda1_setup_dma_pe(phb, pe);
>   		} else if (phb->type == PNV_PHB_IODA2) {
>   			pe_info(pe, "Assign DMA32 space\n");
> -			segs = 0;
>   			pnv_pci_ioda2_setup_dma_pe(phb, pe);
>   		} else if (phb->type == PNV_PHB_NPU) {
>   			/*
> @@ -2611,9 +2615,6 @@ static void pnv_ioda_setup_dma(struct pnv_phb *phb)
>   			 * as the PHB3 TVT.
>   			 */
>   		}
> -
> -		remaining -= segs;
> -		base += segs;
>   	}
>   }
>
> @@ -3313,7 +3314,8 @@ static void __init pnv_pci_init_ioda_phb(struct device_node *np,
>   {
>   	struct pci_controller *hose;
>   	struct pnv_phb *phb;
> -	unsigned long size, m64map_off, m32map_off, pemap_off, iomap_off = 0;
> +	unsigned long size, m64map_off, m32map_off, pemap_off;
> +	unsigned long iomap_off = 0, dma32map_off = 0;
>   	const __be64 *prop64;
>   	const __be32 *prop32;
>   	int i, len;
> @@ -3398,6 +3400,10 @@ static void __init pnv_pci_init_ioda_phb(struct device_node *np,
>   	phb->ioda.io_segsize = phb->ioda.io_size / phb->ioda.total_pe_num;
>   	phb->ioda.io_pci_base = 0; /* XXX calculate this ? */
>
> +	/* Calculate how many 32-bit TCE segments we have */
> +	phb->ioda.dma32_count = phb->ioda.m32_pci_base /
> +				PNV_IODA1_DMA32_SEGSIZE;
> +
>   	/* Allocate aux data & arrays. We don't have IO ports on PHB3 */
>   	size = _ALIGN_UP(phb->ioda.total_pe_num / 8, sizeof(unsigned long));
>   	m64map_off = size;
> @@ -3407,6 +3413,9 @@ static void __init pnv_pci_init_ioda_phb(struct device_node *np,
>   	if (phb->type == PNV_PHB_IODA1) {
>   		iomap_off = size;
>   		size += phb->ioda.total_pe_num * sizeof(phb->ioda.io_segmap[0]);
> +		dma32map_off = size;
> +		size += phb->ioda.dma32_count *
> +			sizeof(phb->ioda.dma32_segmap[0]);
>   	}
>   	pemap_off = size;
>   	size += phb->ioda.total_pe_num * sizeof(struct pnv_ioda_pe);
> @@ -3422,6 +3431,10 @@ static void __init pnv_pci_init_ioda_phb(struct device_node *np,
>   		phb->ioda.io_segmap = aux + iomap_off;
>   		for (i = 0; i < phb->ioda.total_pe_num; i++)
>   			phb->ioda.io_segmap[i] = IODA_INVALID_PE;
> +
> +		phb->ioda.dma32_segmap = aux + dma32map_off;
> +		for (i = 0; i < phb->ioda.dma32_count; i++)
> +			phb->ioda.dma32_segmap[i] = IODA_INVALID_PE;
>   	}
>   	phb->ioda.pe_array = aux + pemap_off;
>   	set_bit(phb->ioda.reserved_pe_idx, phb->ioda.pe_alloc);
> @@ -3430,7 +3443,7 @@ static void __init pnv_pci_init_ioda_phb(struct device_node *np,
>   	mutex_init(&phb->ioda.pe_list_mutex);
>
>   	/* Calculate how many 32-bit TCE segments we have */
> -	phb->ioda.tce32_count = phb->ioda.m32_pci_base /
> +	phb->ioda.dma32_count = phb->ioda.m32_pci_base /
>   				PNV_IODA1_DMA32_SEGSIZE;
>
>   #if 0 /* We should really do that ... */
> diff --git a/arch/powerpc/platforms/powernv/pci.h b/arch/powerpc/platforms/powernv/pci.h
> index e90bcbe..350e630 100644
> --- a/arch/powerpc/platforms/powernv/pci.h
> +++ b/arch/powerpc/platforms/powernv/pci.h
> @@ -146,6 +146,10 @@ struct pnv_phb {
>   		int			*m32_segmap;
>   		int			*io_segmap;
>
> +		/* DMA32 segment maps - IODA1 only */
> +		unsigned long		dma32_count;
> +		int			*dma32_segmap;
> +
>   		/* IRQ chip */
>   		int			irq_chip_init;
>   		struct irq_chip		irq_chip;
> @@ -162,9 +166,6 @@ struct pnv_phb {
>   		 */
>   		unsigned char		pe_rmap[0x10000];
>
> -		/* 32-bit TCE tables allocation */
> -		unsigned long		tce32_count;
> -
>   		/* TCE cache invalidate registers (physical and
>   		 * remapped)
>   		 */
>

-- 
Alexey