Re: x86: Add SPI slaves to PCIe SPI master?

[Alexander Stein <alexander.stein@xxxxxxxxxxxxxxxxxxxxx>]

On Thursday 12 January 2017 14:01:11, Mika Westerberg wrote:
> On Thu, Jan 12, 2017 at 01:48:13PM +0200, Andy Shevchenko wrote:
> > On Wed, Jan 11, 2017 at 5:08 PM, Alexander Stein
> > 
> > <alexander.stein@xxxxxxxxxxxxxxxxxxxxx> wrote:
> > > Hi,
> > > 
> > > I have a customer board using Baytrail E3805 CPU. I want to access a
> > > chip
> > > attached to SPI using spidev.
> > 
> > First of all, this is wrong approach. Do you have a driver for the
> > chip? Are going to develop one?
> > Elaborate, please.

There is no driver and I won't do any either. Can't say much more about that, 
sorry.

> > > but for this the slave has to be attached.
> > > 
> > > This is the corresponding lspci entry:
> > >> 00:1e.5 Serial bus controller [0c80]: Intel Corporation Atom Processor
> > > 
> > > Z36xxx/Z37xxx Series LPIO1 SPI Controller (rev 11)
> > > PCIe vendor and product ID is 8086:0f0e
> > 
> > It's not what we are interested to see :-)
> > 
> > Basically you need
> > a) not ancient kernel (what's version of yours?);

This is a up-to-date archlinux, so I'm running 4.8.13-1-ARCH kernel.

> > b) check proper ACPI node for the PCIe device (something like
> > _SB.PCI0.SPI1).
> You can find the node by running following command
> 
>  # cat /sys/bus/pci/devices/0000:00:1e.5/firmware_node/path

result: \_SB_.PCI0.D023

The node itself is just:
> Device (D023)
> {
>     Name (_ADR, 0x001E0005)  // _ADR: Address
> }

Well, I'm not experienced with ACPI tables at all, but adding a device like in 
the 1st post I got my spi slave device, to my surprise I have to admit.

Thanks for that hint about the, kinda dummy, node for the PCIe device node. I 
didn't expect adding a slave device there would result in having a linux 
device too.

Best regards,
Alexander
-- 
Dipl.-Inf. Alexander Stein
SYS TEC electronic GmbH
alexander.stein@xxxxxxxxxxxxxxxxxxxxx

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