linux-kernel - Re: [PATCH v4 2/2] PCI: iproc: Add outbound configuration for 32-bit I/O region

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Message-ID: <20190329173515.GA10367@e107981-ln.cambridge.arm.com>
Date:   Fri, 29 Mar 2019 17:35:53 +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,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Abhishek Shah <abhishek.shah@...adcom.com>,
        Ray Jui <ray.jui@...adcom.com>
Subject: Re: [PATCH v4 2/2] PCI: iproc: Add outbound configuration for 32-bit
 I/O region

On Fri, Mar 01, 2019 at 10:22:16AM +0530, Srinath Mannam wrote:
> In the present driver outbound window configuration is done to map above
> 32-bit address I/O regions with corresponding PCI memory range given in
> ranges DT property.
> 
> This patch add outbound window configuration to map below 32-bit I/O range
> with corresponding PCI memory, which helps to access I/O region in ARM
> 32-bit and one to one mapping of I/O region to PCI memory.
> 
> Ex:
> 1. ranges DT property given for current driver is,
>     ranges = <0x83000000 0x0 0x40000000 0x4 0x00000000 0 0x40000000>;
>     I/O region address is 0x400000000
> 2. ranges DT property can be given after this patch,
>     ranges = <0x83000000 0x0 0x42000000 0x0 0x42000000 0 0x2000000>;
>     I/O region address is 0x42000000

I was applying this patch but I don't understand the commit log and
how it matches the code, please explain it to me and I will reword
it.

Thanks,
Lorenzo

> 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>
> ---
>  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
> +			 */
> +			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
>