Re: Sierra Wireless EM9191 integration issues in mhi+wwan

[Thomas Perrot <thomas.perrot@bootlin.com>]

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Hi Loic,

On Mon, 2021-10-18 at 11:59 +0200, Loic Poulain wrote:
> Hi Aleksander,
> 
> On Mon, 18 Oct 2021 at 11:14, Aleksander Morgado
> <aleksander@aleksander.es> wrote:
> > 
> > Hey all,
> > 
> > > [    7.056113] mhi-pci-generic 0000:01:00.0: MHI PCI device found:
> > > sierra-em919x
> > > [    7.063298] mhi-pci-generic 0000:01:00.0: BAR 0: assigned [mem
> > > 0x600000000-0x600000fff 64bit]
> > > [    7.071846] mhi-pci-generic 0000:01:00.0: enabling device (0000
> > > -> 0002)
> > > [    7.078671] mhi-pci-generic 0000:01:00.0: using shared MSI
> > 
> > In this specific setup we request 4 MSI vectors through
> > pci_alloc_irq_vectors(), but only end up allocating a single one
> > (i.e.
> > mhi_cntrl->nr_irqs = 1). Could that be related to the problem
> > somehow?
> 
> It shouldn't, we have the 'shared IRQ' fallback which is used when we
> can not setup multiple MSI, and this works with other SDX55 based
> modems.
> 

Compared to other SDX55 based modems, EM919x uses the same event ring
for the control, the data and the diag, and we use the macro
MHI_EVENT_CONFIG_CTRL to configure it.
- Perhaps this macro is not suitable in this case?
- Could this be explaining, what are we observing?

Moreover, we have voluntarily reduced the number of shared MSI vectors
to one, on a platform able to provide enough, then we observe the same
kind of issues, as on i.MX6DL which end up allocating a single one.
However, we carried out this test only with the vendor driver.

Best regards,
Thomas

> Regards,
> Loic

-- 
Thomas Perrot, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com


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