Subject: Re: [PATCH v7 25/50] powerpc/powernv: Reserve PE for root bus

From: Alexey Kardashevskiy <[email-masked]>
Date: Tue, 17 Nov 2015 17:04:42 +1100

On 11/05/2015 12:12 AM, Gavin Shan wrote:
> We're going to reserve/assign PEs when pcibios_setup_bridge() is
> called. The function won't be called for root bus as it doesn't
> have parent bridge. However, the root bus still needs a PE to be
> covered.
>
> This reserves PE numbers that are adjacent to the reserved one
> for root buses.

Somewhere in the patchset you need to describe why you need a separate PE 
for a root bus and why reserved_pe_idx is not enough for this.

>
> Signed-off-by: Gavin Shan <[email-masked]>
> ---
>   arch/powerpc/platforms/powernv/pci-ioda.c | 33 ++++++++++++++++++++++---------
>   arch/powerpc/platforms/powernv/pci.h      |  1 +
>   2 files changed, 25 insertions(+), 9 deletions(-)
>
> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
> index eea1c96..5e6745f 100644
> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
> @@ -207,14 +207,14 @@ static int pnv_ioda2_init_m64(struct pnv_phb *phb)
>   	set_bit(phb->ioda.m64_bar_idx, &phb->ioda.m64_bar_alloc);
>
>   	/*
> -	 * Strip off the segment used by the reserved PE, which is
> -	 * expected to be 0 or last one of PE capabicity.
> +	 * Exclude the segments for reserved and root bus PE, which
> +	 * are first or last two PEs.
>   	 */
>   	r = &phb->hose->mem_resources[1];
>   	if (phb->ioda.reserved_pe_idx == 0)
> -		r->start += phb->ioda.m64_segsize;
> +		r->start += (2 * phb->ioda.m64_segsize);
>   	else if (phb->ioda.reserved_pe_idx == (phb->ioda.total_pe_num - 1))
> -		r->end -= phb->ioda.m64_segsize;
> +		r->end -= (2 * phb->ioda.m64_segsize);
>   	else
>   		pr_warn("  Cannot strip M64 segment for reserved PE#%d\n",
>   			phb->ioda.reserved_pe_idx);
> @@ -294,14 +294,14 @@ static int pnv_ioda1_init_m64(struct pnv_phb *phb)
>   	}
>
>   	/*
> -	 * Exclude the segment used by the reserved PE, which
> -	 * is expected to be 0 or last supported PE#.
> +	 * Exclude the segments for reserved and root bus PE, which
> +	 * are first or last two PEs.
>   	 */
>   	r = &phb->hose->mem_resources[1];
>   	if (phb->ioda.reserved_pe_idx == 0)
> -		r->start += phb->ioda.m64_segsize;
> +		r->start += (2 * phb->ioda.m64_segsize);
>   	else if (phb->ioda.reserved_pe_idx == (phb->ioda.total_pe_num - 1))
> -		r->end -= phb->ioda.m64_segsize;
> +		r->end -= (2 * phb->ioda.m64_segsize);
>   	else
>   		pr_warn("  Cannot cut M64 segment for reserved PE#%d\n",
>   			phb->ioda.reserved_pe_idx);
> @@ -3231,7 +3231,22 @@ static void __init pnv_pci_init_ioda_phb(struct device_node *np,
>   			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);
> +
> +	/*
> +	 * Choose PE number for root bus, which shouldn't have
> +	 * M64 resources consumed by its child devices. To pick
> +	 * the PE number adjacent to the reserved one if possible.
> +	 */
> +	pnv_ioda_reserve_pe(phb, phb->ioda.reserved_pe_idx);
> +	if (phb->ioda.reserved_pe_idx == 0) {
> +		phb->ioda.root_pe_idx = 1;
> +		pnv_ioda_reserve_pe(phb, phb->ioda.root_pe_idx);
> +	} else if (phb->ioda.reserved_pe_idx == (phb->ioda.total_pe_num - 1)) {
> +		phb->ioda.root_pe_idx = phb->ioda.reserved_pe_idx - 1;
> +		pnv_ioda_reserve_pe(phb, phb->ioda.root_pe_idx);
> +	} else {
> +		phb->ioda.root_pe_idx = IODA_INVALID_PE;
> +	}
>
>   	INIT_LIST_HEAD(&phb->ioda.pe_list);
>   	mutex_init(&phb->ioda.pe_list_mutex);
> diff --git a/arch/powerpc/platforms/powernv/pci.h b/arch/powerpc/platforms/powernv/pci.h
> index e55ab0e..a8ba97f 100644
> --- a/arch/powerpc/platforms/powernv/pci.h
> +++ b/arch/powerpc/platforms/powernv/pci.h
> @@ -120,6 +120,7 @@ struct pnv_phb {
>   			/* Global bridge info */
>   			unsigned int		total_pe_num;
>   			unsigned int		reserved_pe_idx;
> +			unsigned int		root_pe_idx;
>
>   			/* 32-bit MMIO window */
>   			unsigned int		m32_size;
>

-- 
Alexey