Re: [PATCH 02/11] PCI: altera: Use pci_parse_request_of_pci_ranges()

From: Andrew Murray <andrew.murray@arm.com>
To: Rob Herring <robh@kernel.org>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	linux-pci@vger.kernel.org, rfi@lists.rocketboards.org,
	Bjorn Helgaas <bhelgaas@google.com>,
	Ley Foon Tan <lftan@altera.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 02/11] PCI: altera: Use pci_parse_request_of_pci_ranges()
Date: Wed, 25 Sep 2019 11:24:23 +0100	[thread overview]
Message-ID: <20190925102423.GR9720@e119886-lin.cambridge.arm.com> (raw)
In-Reply-To: <20190924214630.12817-3-robh@kernel.org>

On Tue, Sep 24, 2019 at 04:46:21PM -0500, Rob Herring wrote:
> Convert altera host bridge to use the common
> pci_parse_request_of_pci_ranges().
> 
> Cc: Ley Foon Tan <lftan@altera.com>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: rfi@lists.rocketboards.org
> Signed-off-by: Rob Herring <robh@kernel.org>
> ---
>  drivers/pci/controller/pcie-altera.c | 38 ++--------------------------
>  1 file changed, 2 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-altera.c b/drivers/pci/controller/pcie-altera.c
> index d2497ca43828..2ed00babff5a 100644
> --- a/drivers/pci/controller/pcie-altera.c
> +++ b/drivers/pci/controller/pcie-altera.c
> @@ -670,39 +670,6 @@ static void altera_pcie_isr(struct irq_desc *desc)
>  	chained_irq_exit(chip, desc);
>  }
>  
> -static int altera_pcie_parse_request_of_pci_ranges(struct altera_pcie *pcie)
> -{
> -	int err, res_valid = 0;
> -	struct device *dev = &pcie->pdev->dev;
> -	struct resource_entry *win;
> -
> -	err = devm_of_pci_get_host_bridge_resources(dev, 0, 0xff,
> -						    &pcie->resources, NULL);
> -	if (err)
> -		return err;
> -
> -	err = devm_request_pci_bus_resources(dev, &pcie->resources);
> -	if (err)
> -		goto out_release_res;
> -
> -	resource_list_for_each_entry(win, &pcie->resources) {
> -		struct resource *res = win->res;
> -
> -		if (resource_type(res) == IORESOURCE_MEM)
> -			res_valid |= !(res->flags & IORESOURCE_PREFETCH);
> -	}
> -
> -	if (res_valid)
> -		return 0;
> -
> -	dev_err(dev, "non-prefetchable memory resource required\n");
> -	err = -EINVAL;
> -
> -out_release_res:
> -	pci_free_resource_list(&pcie->resources);
> -	return err;
> -}
> -
>  static int altera_pcie_init_irq_domain(struct altera_pcie *pcie)
>  {
>  	struct device *dev = &pcie->pdev->dev;
> @@ -833,9 +800,8 @@ static int altera_pcie_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> -	INIT_LIST_HEAD(&pcie->resources);
> -
> -	ret = altera_pcie_parse_request_of_pci_ranges(pcie);
> +	ret = pci_parse_request_of_pci_ranges(dev, &pcie->resources,

Does it matter that we now map any given IO ranges whereas we didn't
previously?

As far as I can tell there are no users that pass an IO range, if they
did then with the existing code the probe would fail and they'd get
a "I/O range found for %pOF. Please provide an io_base pointer...".
However with the new code if any IO range was given (which would
probably represent a misconfiguration), then we'd proceed to map the
IO range. When that IO is used, who knows what would happen.

I wonder if there is a better way for a host driver to indicate that
it doesn't support IO?

Thanks,

Andrew Murray

> +					      NULL);
>  	if (ret) {
>  		dev_err(dev, "Failed add resources\n");
>  		return ret;
> -- 
> 2.20.1
> 
> 
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