Re: [RFC RFT PATCH v1 0/1] ARM: orion5x: convert D-Link DNS-323 to the Device Tree

["Pali Rohár" <pali@kernel.org>]

On Sunday 08 May 2022 17:22:37 Pali Rohár wrote:
> On Sunday 08 May 2022 17:02:17 Arnd Bergmann wrote:
> > On Sun, May 8, 2022 at 4:06 PM Mauri Sandberg <maukka@ext.kapsi.fi> wrote:
> > > On 28.4.2022 23.56, Arnd Bergmann wrote:
> > > > On Thu, Apr 28, 2022 at 10:01 PM Mauri Sandberg <maukka@ext.kapsi.fi> wrote:
> > > >> On 27.4.2022 21.10, Arnd Bergmann wrote:
> > > >>> On Wed, Apr 27, 2022 at 6:21 PM Mauri Sandberg <maukka@ext.kapsi.fi> wrote:
> > > >>>> - sata_mv fails to initialise with -22 (-EINVAL)
> > > >>>
> > > >>> No idea, I'd try inserting a printk in every code path that can return -EINVAL
> > > >>> from there
> > > >>>
> > >
> > > With debugging the reason for -EINVAL remains a bit mystery.
> > >   - sata_mv calls ata_host_activate() [1]
> > >   - later on, in request_threaded_irq(), there are sanity checks [2]
> > >   - that fail with irq_settings_can_request() returning 0 [3]
> > >
> > > I cannot really put my finger on why the irq cannot be requested in DT
> > > approach.
> > 
> > Are you sure the marvell,orion-intc driver is successfully probed
> > at this point? If not, the interrupt won't be there.
> > 
> > I see that the "sata_mv" driver can be used either as a platform
> > driver for the orion5x on-chip controller, or as a PCI driver for
> > an add-on chip connected to the external bus. It sounds like
> > your system has both. Do you know which one fails?
> > 
> > The PCI driver cannot work unless the PCI host works correctly,
> > and that in turn requires a correct devicetree description for it.
> > 
> > > >> Is there a way to describe the PCIe bus in the
> > > >> device tree? The initalisation of that bus is done for rev A1 only.
> > > >
> > > > I'm not too familiar with the platform, but my interpretation is that the
> > > > DT support here is incomplete:
> > > >
> > > > The DT based PCI probe using drivers/pci/controller/pci-mvebu.c
> > > > is not hooked up in orion5x.dtsi, and the traditional pci code does
> > > > not work with DT.
> > >
> > > Can the existing pci code still be used to init the PCI bus and describe
> > > the rest in the DT or is it a futile attempt?
> 
> Hello! Orion uses arch/arm/mach-orion5x/pci.c driver for both PCI and
> PCIe buses. This is not device tree driver.

Correction, Orion PCIe driver is arch/arm/plat-orion/pcie.c and it calls
common functions from mach-orion5x/pci.c driver.

> > > > I see that orion5x has two separate blocks --  a PCIe host that is
> > > > similar to the kirkwood one, and a legacy PCI host that needs
> > > > a completely separate driver.
> > > >
> > > > Which of the two do you actually need here?
> > > >
> > >
> > > I really cannot say which one is it. How can I tell? The functions given
> > > in struct hw_pci find their way to drivers/pci/probe.c eventually and
> > > use pci_scan_root_bus_bridge(). Nothing seems to utilising mvebu or
> > > kirkwood explicitly at least.
> > >
> > > Here's the output from lspci if the ids reveal anything.
> > >
> > > # lspci -v -k
> > > 00:00.0 Class 0580: 11ab:5181
> > > 01:00.0 Class 0580: 11ab:5181
> > > 00:01.0 Class 0100: 11ab:7042 sata_mv
> > 
> > The first two seem to be the host bridges, but unfortunately they
> >  seem both have the same device ID, despite being very different
> > devices.  The first one (00:00.0) should be the PCIe driver, the
> > second one (01.00.0) the legacy PCI one. In this case, the 11ab:7042
> > device is a PCIe device, and it's on the bus (00) of the first host
> > bridge. I think this should work with drivers/pci/controller/pci-mvebu.c
> > if you add the bits for probing.
> 
> Last time when I looked on Orion PCIe controller registers, I though
> that they are same as in Kirkwood PCIe controller registers. And
> Kirkwood is already supported by pci-mvebu.c driver.
> 
> About PCI host bridge, I do not know.
> 
> Beware that PCI Class Id and all PCI registers which are different for
> Type 0 and Type 1 are _broken_ on all PCIe Root Ports form all 32-bit
> Marvell SoCs. Those registers on Marvell SoCs have different meaning as
> what is defined in PCI and PCIe specs. So it means that lspci _may_
> display bogus information about PCIe Root Port. pci-mvebu.c uses Root
> Port emulator which fills correct data to make kernel and lspci happy.
> 
> If you are going to extend pci-mvebu.c to support also Orion PCIe
> controller, I could try to help with it. But I do not have any Orion
> hardware, so just basic help...
> 
> Links to Orion documentations, including PCIe errata is available in
> kernel documentation. So this could help to understand some details:
> https://www.kernel.org/doc/html/latest/arm/marvell.html
> 
> Anyway, could you please provide 'lspci -nn -vv' and 'lspci -nn -t -v'
> outputs from Orion?
> 
> > Thomas Petazzoni originally wrote the new driver, and I think he was
> > planning at one point to use it for orion5x. I don't know if there were
> > any major problems preventing this at the time, or if it just needs to
> > get hooked up in the dtsi file.
> > 
> >          Arnd

There is Orion-specific errata that config space via CF8/CFC registers
is broken. Workaround documented in errata documented (linked from above
documentation) does not work when DMA is used and instead other
undocumented workaround is needed (implemented in arch/arm) which maps
config space to memory (and therefore avoids usage of broken CF8/CFC
memory mapped registers).

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