Re: [PATCH 1/2] PCI: vmd: Add bus 224-255 restriction decode

From: Keith Busch <kbusch@kernel.org>
To: Jon Derrick <jonathan.derrick@intel.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	linux-pci@vger.kernel.org, Bjorn Helgaas <helgaas@kernel.org>,
	Keith Busch <kbusch@kernel.com>
Subject: Re: [PATCH 1/2] PCI: vmd: Add bus 224-255 restriction decode
Date: Tue, 12 Nov 2019 02:04:22 +0900	[thread overview]
Message-ID: <20191111170422.GB10851@redsun51.ssa.fujisawa.hgst.com> (raw)
In-Reply-To: <20191111165302.29636-2-jonathan.derrick@intel.com>

On Mon, Nov 11, 2019 at 09:53:01AM -0700, Jon Derrick wrote:
> VMD bus restrictions are required when IO fabric is multiplexed such
> that VMD cannot use the entire bus range. This patch adds another bus
> restriction decode bit that can be set by firmware to restrict the VMD
> bus range from 224-255.

The code suggests that such a device is restricted *to* that range,
not from it.

> +			switch (BUS_RESTRICT_CFG(reg16)) {
> +			case(1):
> +				vmd->busn_start = 128;
> +				break;
> +			case(2):
> +				vmd->busn_start = 224;
> +				break;
> +			case(3):
> +				pci_err(vmd->dev, "Unknown Bus Offset Setting\n");
> +				return -ENODEV;
> +			default:
> +				break;
> +			}

Just a nit for consistent sytle, every other switch case looks like:

	case 1:
		...
	case 2:
		...
	case 3:
		...