linux-kernel - Re: [PATCH v2 2/2] PCI: iproc: Add PCIe 32bit outbound memory configuration

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Date:   Tue, 12 Feb 2019 18:37:39 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Srinath Mannam <srinath.mannam@...adcom.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com, linux-pci@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Abhishek Shah <abhishek.shah@...adcom.com>,
        Ray Jui <ray.jui@...adcom.com>
Subject: Re: [PATCH v2 2/2] PCI: iproc: Add PCIe 32bit outbound memory
 configuration

On Tue, Feb 05, 2019 at 10:27:01AM +0530, Srinath Mannam wrote:
> Add configuration to support IPROC PCIe host controller outbound memory
> window mapping with SOC address range inside 4GB boundary, which is 32 bit
> AXI address.

I do not understand what this means, explain it to me and rewrite the
commit log accordingly.

What does this solve ? Why do we need this patch or rephrased, what
is missing in the current driver ?

> Signed-off-by: Srinath Mannam <srinath.mannam@...adcom.com>
> Signed-off-by: Abhishek Shah <abhishek.shah@...adcom.com>
> Signed-off-by: Ray Jui <ray.jui@...adcom.com>
> Reviewed-by: Scott Branden <scott.branden@...adcom.com>
> Reviewed-by: Vikram Prakash <vikram.prakash@...adcom.com>

Review tags should be given on public mailing lists, these ones seem
to come from non-public review cycles in which case you must drop
them.

>  drivers/pci/controller/pcie-iproc.c | 21 +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-iproc.c b/drivers/pci/controller/pcie-iproc.c
> index b882255..080f142 100644
> --- a/drivers/pci/controller/pcie-iproc.c
> +++ b/drivers/pci/controller/pcie-iproc.c
> @@ -955,8 +955,25 @@ static int iproc_pcie_setup_ob(struct iproc_pcie *pcie, u64 axi_addr,
>  			resource_size_t window_size =
>  				ob_map->window_sizes[size_idx] * SZ_1M;
>  
> -			if (size < window_size)
> -				continue;
> +			/*
> +			 * Keep iterating until we reach the last window and
> +			 * with the minimal window size at index zero. In this
> +			 * case, we take a compromise by mapping it using the
> +			 * minimum window size that can be supported

See above, I do not understand clearly what this means.

Lorenzo

> +			 */
> +			if (size < window_size) {
> +				if (size_idx > 0 || window_idx > 0)
> +					continue;
> +
> +				/*
> +				 * For the corner case of reaching the minimal
> +				 * window size that can be supported on the
> +				 * last window
> +				 */
> +				axi_addr = ALIGN_DOWN(axi_addr, window_size);
> +				pci_addr = ALIGN_DOWN(pci_addr, window_size);
> +				size = window_size;
> +			}
>  
>  			if (!IS_ALIGNED(axi_addr, window_size) ||
>  			    !IS_ALIGNED(pci_addr, window_size)) {
> -- 
> 2.7.4
>