linux-kernel - Re: [PATCH v4 3/3] PCI: imx6: limit DBI register length

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Date:   Tue, 4 Dec 2018 19:08:50 +0000
From:   Leonard Crestez <leonard.crestez@....com>
To:     "stefan@...er.ch" <stefan@...er.ch>
CC:     Richard Zhu <hongxing.zhu@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jingoohan1@...il.com" <jingoohan1@...il.com>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "gustavo.pimentel@...opsys.com" <gustavo.pimentel@...opsys.com>,
        "tpiepho@...inj.com" <tpiepho@...inj.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>
Subject: Re: [PATCH v4 3/3] PCI: imx6: limit DBI register length

On Tue, 2018-12-04 at 17:55 +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
> 
>  static const struct imx6_pcie_drvdata drvdata[] = {
> -	[IMX6Q] = { .variant = IMX6Q },
> +	[IMX6Q] = { .variant = IMX6Q, .dbi_length = 0x15c },
>  	[IMX6SX] = { .variant = IMX6SX },
>  	[IMX6QP] = { .variant = IMX6QP },
>  	[IMX7D] = { .variant = IMX7D },

Also seems to affect IMX6QP variant (but not others).

Lucas suggested 0x15c because that's the last register documented in
the datasheet but the real HW limit is 0x200, wouldn't it make more
sense to use that?

--
Regards,
Leonard