Re: bcm2711 / RPi4 not functional after d62069c22eda

[Lukas Wunner <lukas@xxxxxxxxx>]

[cc += linux-spi; please do not write developers directly without cc'ing
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On Fri, Mar 18, 2022 at 11:54:35AM +0100, Miguel Angel Ajo wrote:
> On Fri, Mar 18, 2022 at 11:47 AM Miguel Angel Ajo <majopela@xxxxxxxxxx>
> wrote:
> >     I wanted to share a regression found after commit:
> >
> > d62069c22eda spi: bcm2835: Remove shared interrupt support
[...]
> > After this commit I get:
> >
> > [root@rpi4-64 ~]# dmesg | grep spi
> > [   18.781250] spi-bcm2835 fe204000.spi: could not register SPI
> > controller: -517
> > [   19.134138] spi-bcm2835 fe204000.spi: could not register SPI
> > controller: -517
> > [   19.895147] spi-bcm2835 fe204000.spi: could not register SPI
> > controller: -517
> > [   20.400137] spi-bcm2835 fe204000.spi: could not register SPI
> > controller: -517

Those are transient errors, -517 is -EPROBE_DEFER.  Probing fails
because a resource is not available (yet), to be retried again later
if/when it becomes available.


> > ecfbd3c introduced support for the bcm2711 SoC that shares
> > one interrupt over multiple spi controller instances.
> >
> > Do we have a more detailed description of the exact issue for
> > which we reverted?, is there a plan to re-introduce the shared interrupt
> > support while fixing the issue?

See here for why the commit was reverted:

https://lore.kernel.org/linux-spi/20200529174358.som3snunfxch6phi@xxxxxxxxx/

There was a second attempt to introduce shared interrupt support,
but after a lengthy discussion, it was not pursued to fruition:

https://lore.kernel.org/linux-spi/20200604212819.715-1-f.fainelli@xxxxxxxxx/

So I believe shared interrupt support only exists in the Raspberry Pi
Foundation's downstream kernel, but not yet in the mainline kernel.

Thanks,

Lukas