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From: Peter Maydell <peter.maydell@linaro.org>
Date: Thu, 8 Mar 2018 10:50:42 +0000
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Subject: Re: [Qemu-devel] [PATCH] fsl-imx6: Swap Ethernet interrupt defines
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To: Guenter Roeck <linux@roeck-us.net>
Cc: QEMU Developers <qemu-devel@nongnu.org>, Andrey Smirnov <andrew.smirnov@gmail.com>, Chris Healy <cphealy@gmail.com>, Jason Wang <jasowang@redhat.com>, Jean-Christophe Dubois <jcd@tribudubois.net>, Bill Paul <wpaul@windriver.com>

On 7 March 2018 at 17:37, Guenter Roeck <linux@roeck-us.net> wrote:
> The sabrelite machine model used by qemu-system-arm is based on the
> Freescale/NXP i.MX6Q processor. This SoC has an on-board ethernet
> controller which is supported in QEMU using the imx_fec.c module
> (actually called imx.enet for this model.)
>
> The include/hw/arm/fsm-imx6.h file defines the interrupt vectors for the
> imx.enet device like this:
>
>  #define FSL_IMX6_ENET_MAC_1588_IRQ 118
>  #define FSL_IMX6_ENET_MAC_IRQ 119
>
> According to https://www.nxp.com/docs/en/reference-manual/IMX6DQRM.pdf,
> page 225, in Table 3-1. ARM Cortex A9 domain interrupt summary,
> interrupts are as follows.
>
> 150 ENET MAC 0 IRQ
> 151 ENET MAC 0 1588 Timer interrupt
>
> where
>
> 150 - 32 == 118
> 151 - 32 == 119
>
> In other words, the vector definitions in the fsl-imx6.h file are reversed.
>
> This results in lost interrupt warnings when running recent (v4.15+) Linux
> kernels, and the Ethernet interface will fail to probe.
>
> Note that applying this patch will cause problems with older Linux kernels:
> The Ethernet interface will fail to probe with Linux v4.9 and earlier.
> Linux v4.1 and earlier will crash. This is a Linux kernel problem, not a
> qemu problem: the Linux kernel only worked by accident since it requested
> both interrupts.

So do the works-by-accident kernels fail on QEMU because
we don't emulate some bit of the ethernet device ?
Ideally we could fix that so we could boot newer kernels
without breaking the old ones...

thanks
-- PMM