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SubjectRe: [PATCH 2/2] PCI: imx6: limit DBI register length
On Wed, Feb 06, 2019 at 10:57:32AM +0100, Stefan Agner wrote:
> Define the length of the DBI registers. This makes sure that
> the kernel does not access registers beyond that point, avoiding
> the following abort on a i.MX 6Quad:
> # cat /sys/devices/soc0/soc/1ffc000.pcie/pci0000\:00/0000\:00\:00.0/config
> [ 100.021433] Unhandled fault: imprecise external abort (0x1406) at 0xb6ea7000
> ...
> [ 100.056423] PC is at dw_pcie_read+0x50/0x84
> [ 100.060790] LR is at dw_pcie_rd_own_conf+0x44/0x48
> ...

I assume this problem happens when using the pci_read_config() path or
something similar?

Could this be solved using pci_dev.cfg_size instead of building a new
dwc-specific mechanism? There are some quirks that set dev->cfg_size
to keep from reading past certain points in config space, e.g.,
quirk_citrine(), quirk_nfp6000().

I'm not necessarily opposed to doing it in dwc, but maybe there's some
advantage in reducing the number of ways of doing the same thing.

> Signed-off-by: Stefan Agner <stefan@agner.ch>
> Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
> ---
> Changes in v3:
> - Rebase on pci/dwc
> Changes in v4:
> - Rebase on pci/dwc
> Changes in v5:
> - Rebased ontop of pci/dwc
> - Use DBI length of 0x200
>
> drivers/pci/controller/dwc/pci-imx6.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index c1d434ba3642..1ef7be1232f3 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -55,6 +55,7 @@ enum imx6_pcie_variants {
> struct imx6_pcie_drvdata {
> enum imx6_pcie_variants variant;
> u32 flags;
> + int dbi_length;
> };
>
> struct imx6_pcie {
> @@ -1087,6 +1088,8 @@ static int imx6_pcie_probe(struct platform_device *pdev)
> break;
> }
>
> + pci->dbi_length = imx6_pcie->drvdata->dbi_length;
> +
> /* Grab turnoff reset */
> imx6_pcie->turnoff_reset = devm_reset_control_get_optional_exclusive(dev, "turnoff");
> if (IS_ERR(imx6_pcie->turnoff_reset)) {
> @@ -1170,6 +1173,7 @@ static const struct imx6_pcie_drvdata drvdata[] = {
> .variant = IMX6Q,
> .flags = IMX6_PCIE_FLAG_IMX6_PHY |
> IMX6_PCIE_FLAG_IMX6_SPEED_CHANGE,
> + .dbi_length = 0x200,
> },
> [IMX6SX] = {
> .variant = IMX6SX,
> --
> 2.20.1
>

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