Re: [PATCH v6 0/5] PCI: Unify ECAM constants in native PCI Express drivers

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Dec 09, 2020 at 10:29:04PM +0200, Vladimir Oltean wrote:
> On Wed, Dec 09, 2020 at 04:40:52PM +0100, Michael Walle wrote:
> > Hopefully my mail client won't mess up the output that much.
> 
> I can reproduce on my LS1028A as well. The following fixes the bug for
> me. I did not follow the discussion and see if it is helpful for others.
> I don't understand how the bug came to be. There might be more to it
> than what I'm seeing. If it's just what I'm seeing, then the patch was
> pretty broken to begin with.

I squashed the fix below into a pci/ecam branch for v5.11, thanks!

> -----------------------------[cut here]-----------------------------
> From b184da4088c9d39d25fee2486941cdf77688a409 Mon Sep 17 00:00:00 2001
> From: Vladimir Oltean <vladimir.oltean@nxp.com>
> Date: Wed, 9 Dec 2020 22:17:32 +0200
> Subject: [PATCH] PCI: fix invalid window size for the ECAM config space
> 
> The blamed commit forgot that pci_ecam_create() calculates the size of
> the window for the ECAM's config space based on the spacing between two
> buses. The drivers whose .bus_shift from struct pci_ecam_ops was changed
> to zero in this commit are now using this invalid value for bus_shift
> in calculating the window size.
> 
> Before (broken):
> pci_ecam_create: remapping config space from addr 0x1f0000000, bus_range 0x1, bsz 0x1
> After (fixed/restored):
> pci_ecam_create: remapping config space from addr 0x1f0000000, bus_range 0x1, bsz 0x100000
> 
> Fixes: f3c07cf6924e ("PCI: Unify ECAM constants in native PCI Express drivers")
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> ---
>  drivers/pci/ecam.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/ecam.c b/drivers/pci/ecam.c
> index 59f91d434859..9fda0d49bc93 100644
> --- a/drivers/pci/ecam.c
> +++ b/drivers/pci/ecam.c
> @@ -28,11 +28,19 @@ struct pci_config_window *pci_ecam_create(struct device *dev,
>  		struct resource *cfgres, struct resource *busr,
>  		const struct pci_ecam_ops *ops)
>  {
> +	unsigned int bus_shift = ops->bus_shift;
>  	struct pci_config_window *cfg;
>  	unsigned int bus_range, bus_range_max, bsz;
>  	struct resource *conflict;
>  	int i, err;
>  
> +	/*
> +	 * struct pci_ecam_ops may omit specifying bus_shift
> +	 * if it is as per spec
> +	 */
> +	if (!bus_shift)
> +		bus_shift = PCIE_ECAM_BUS_SHIFT;
> +
>  	if (busr->start > busr->end)
>  		return ERR_PTR(-EINVAL);
>  
> @@ -46,14 +54,14 @@ struct pci_config_window *pci_ecam_create(struct device *dev,
>  	cfg->busr.end = busr->end;
>  	cfg->busr.flags = IORESOURCE_BUS;
>  	bus_range = resource_size(&cfg->busr);
> -	bus_range_max = resource_size(cfgres) >> ops->bus_shift;
> +	bus_range_max = resource_size(cfgres) >> bus_shift;
>  	if (bus_range > bus_range_max) {
>  		bus_range = bus_range_max;
>  		cfg->busr.end = busr->start + bus_range - 1;
>  		dev_warn(dev, "ECAM area %pR can only accommodate %pR (reduced from %pR desired)\n",
>  			 cfgres, &cfg->busr, busr);
>  	}
> -	bsz = 1 << ops->bus_shift;
> +	bsz = 1 << bus_shift;
>  
>  	cfg->res.start = cfgres->start;
>  	cfg->res.end = cfgres->end;
> -----------------------------[cut here]-----------------------------