GPIOs on CS5536 based boards

[Daniel Mack]

Hi,

I'm developing on a CS5536 based board (ALIX.2D) and I'm trying to get
access to the GPIO registers in order to set the LEDs on bootup.

However, I seem to miss an mandatory point when trying so. As a quick
hack, I added these lines to the end of southbridge_init() in
coreboot-v3/southbridge/amd/cs5536/cs5536.c:

outl(GPIOL_6_SET, GPIO_IO_BASE + GPIOL_OUTPUT_ENABLE);
  outl(GPIOL_6_CLEAR, GPIO_IO_BASE + GPIOL_OUTPUT_VALUE);

According to the schematics, GPIO6 is connected to one of the LEDs found
on the board, but the GPIO level does not change. I tried reading back
another GPIO but the READ_BACK register reads 0xffffffff, even though
the uppermost 16 bits are supposed to be 0 always. So I assume I missed
some basic point.

The MSR mapping should be set up at this point, as there are accesses to
other GPIO related registers called from the same function.

Any pointers, anyone?

Thanks,
Daniel

[Peter Stuge]

Daniel Mack wrote:
> I'm developing on a CS5536 based board (ALIX.2D) and I'm trying to
> get access to the GPIO registers in order to set the LEDs on
> bootup.

Check out the 5536 data book on "Atomic Bit Programming" and/or look
at the Linux LED driver for reference. To program the GPIOs you have
to follow the algorithm outlined in 6.16.1.

//Peter

[ron minnich]

On Tue, Sep 22, 2009 at 4:56 AM, Peter Stuge  wrote:
> Daniel Mack wrote:
> Check out the 5536 data book on "Atomic Bit Programming" and/or look
> at the Linux LED driver for reference. To program the GPIOs you have
> to follow the algorithm outlined in 6.16.1.

Yes, this is a pretty elegant idea the Geode guys created that is,
sadly, not in anything else.

ron

[Daniel Mack]

On Tue, Sep 22, 2009 at 01:56:53PM +0200, Peter Stuge wrote:
> Daniel Mack wrote:
> > I'm developing on a CS5536 based board (ALIX.2D) and I'm trying to
> > get access to the GPIO registers in order to set the LEDs on
> > bootup.
>
> Check out the 5536 data book on "Atomic Bit Programming" and/or look
> at the Linux LED driver for reference. To program the GPIOs you have
> to follow the algorithm outlined in 6.16.1.

Hmm. I followed that guideline, and did the same thing than the Linux
driver, but it still doesn't work. I only found one location from where
I could successfully write to the GPIO registers, and that is
hardware_stage1() in mainboard/pcengines/alix2c3/stage.c.

When moving the same code to southbridge_init() in
southbridge/amd/cs5536/cs5536.c, the register accesses fail.

Also, when booting Linux, the LED driver does not work with coreboot
for me. The register space mapping seems to be given up at some point
on the way, but I can't figure out where and why yet. As I don't know
coreboot's internals, I'd appreciate any pointer.

Thanks,
Daniel

[Daniel Mack]

On Wed, Sep 23, 2009 at 06:03:38AM +0200, Daniel Mack wrote:
> On Tue, Sep 22, 2009 at 01:56:53PM +0200, Peter Stuge wrote:
> > Check out the 5536 data book on "Atomic Bit Programming" and/or look
> > at the Linux LED driver for reference. To program the GPIOs you have
> > to follow the algorithm outlined in 6.16.1.
>
> Hmm. I followed that guideline, and did the same thing than the Linux
> driver, but it still doesn't work. I only found one location from where
> I could successfully write to the GPIO registers, and that is
> hardware_stage1() in mainboard/pcengines/alix2c3/stage.c.
>
> When moving the same code to southbridge_init() in
> southbridge/amd/cs5536/cs5536.c, the register accesses fail.
>
> Also, when booting Linux, the LED driver does not work with coreboot
> for me. The register space mapping seems to be given up at some point
> on the way, but I can't figure out where and why yet. As I don't know
> coreboot's internals, I'd appreciate any pointer.

I traced a little further and implemented a cs5536_set_resources() which
simply wraps the call to pci_set_resources(). GPIO registers are
accessed ok before pci_set_resources() but fail after.

This is the output of print_resource_tree() of the device used:

(CB)  PCI: 00:0f.0 links 0 child on link 0 NULL
(CB)  PCI: 00:0f.0 resource base 0 size 1000 align 0 gran 0 limit 0 flags e0000100 index 0
(CB)  PCI: 00:0f.0 resource base 20b0 size 8 align 3 gran 3 limit ffff flags 40000100 index 10
(CB)  PCI: 00:0f.0 resource base 1800 size 100 align 8 gran 8 limit ffff flags 40000100 index 14
(CB)  PCI: 00:0f.0 resource base 2000 size 40 align 6 gran 6 limit ffff flags 40000100 index 18
(CB)  PCI: 00:0f.0 resource base 2080 size 20 align 5 gran 5 limit ffff flags 40000100 index 1c
(CB)  PCI: 00:0f.0 resource base 1c00 size 80 align 7 gran 7 limit ffff flags 40000100 index 20
(CB)  PCI: 00:0f.0 resource base 2040 size 40 align 6 gran 6 limit ffff flags 40000100 index 24

Any ideas?

Daniel

[Myles Watson]

> I traced a little further and implemented a cs5536_set_resources() which
> simply wraps the call to pci_set_resources(). GPIO registers are
> accessed ok before pci_set_resources() but fail after.

Sounds like the address where you access the resource is changing after
resource allocation.  You have a couple of options:
1. Use the new address after pci_set_resources
2. Don't use pci_set_resources to allocate that resource
    (Set up that resource as fixed)

I think #1 is the best, unless you have to have that address at a specific
location.
> This is the output of print_resource_tree() of the device used:

I don't know enough about it to know which of these resources is the one
you're looking for, but you can look through the code to see where the GPIO
registers are set up.
> (CB)  PCI: 00:0f.0 links 0 child on link 0 NULL
> (CB)  PCI: 00:0f.0 resource base 0 size 1000 align 0 gran 0 limit 0 flags
> e0000100 index 0
> (CB)  PCI: 00:0f.0 resource base 20b0 size 8 align 3 gran 3 limit ffff
> flags 40000100 index 10
> (CB)  PCI: 00:0f.0 resource base 1800 size 100 align 8 gran 8 limit ffff
> flags 40000100 index 14
> (CB)  PCI: 00:0f.0 resource base 2000 size 40 align 6 gran 6 limit ffff
> flags 40000100 index 18
> (CB)  PCI: 00:0f.0 resource base 2080 size 20 align 5 gran 5 limit ffff
> flags 40000100 index 1c
> (CB)  PCI: 00:0f.0 resource base 1c00 size 80 align 7 gran 7 limit ffff
> flags 40000100 index 20
> (CB)  PCI: 00:0f.0 resource base 2040 size 40 align 6 gran 6 limit ffff
> flags 40000100 index 24

Good luck,
Myles

[Ward Vandewege]

On Wed, Sep 23, 2009 at 06:03:38AM +0200, Daniel Mack wrote:
> Also, when booting Linux, the LED driver does not work with coreboot
> for me.

Yeah, known issue. The linux kernel driver stupidly assumes that all firmware
sets up the GPIOs at the same IO port. The kernel driver should look up the
msr and then do the right thing, but it does not.

I think Peter Stuge may have a patch for the LED driver...

Thanks,
Ward.

[Peter Stuge]

Daniel Mack wrote:
> Also, when booting Linux, the LED driver does not work with
> coreboot for me.

The issue is that the driver is using a hard coded base address
rather than finding out what is actually programmed into the device,
and because coreboot doesn't assign resources exactly like the
factory BIOS, the driver can't find the hardware.

The driver should be improved to read the base address from the MSR,
then it would work everywhere.

Another sad fact is that the driver scans the BIOS 0xf0000 segment
for a particular string which is present in the factory BIOS, but not
in coreboot. I believe there is an override.

You may find msrtool helpful since it knows a bit about Geode,
although not nearly everything. It's good with the DIVIL and
interrupts.

boot factory BIOS
# msrtool -l -s file
this saves a list of known MSRs along with their values into file

boot coreboot
# msrtool -d file
this shows decoded MSR differences between saved and current values

//Peter

[Peter Stuge]

Ward Vandewege wrote:
> I think Peter Stuge may have a patch for the LED driver...

If I do it's on a hard drive that I can't find anymore. It's not a
terribly complex change, but the mere thought of cloning the led-2.6
tree is a little exhausting.

//Peter

[Myles Watson]

On Wed, Sep 23, 2009 at 9:52 AM, Peter Stuge  wrote:
> Daniel Mack wrote:
> > Also, when booting Linux, the LED driver does not work with
> > coreboot for me.
>
> The issue is that the driver is using a hard coded base address
> rather than finding out what is actually programmed into the device,
> and because coreboot doesn't assign resources exactly like the
> factory BIOS, the driver can't find the hardware.

Depending on the address, that could be easy to fix.  If it is below 0x1000
it is almost trivial.

Thanks,
Myles

[Peter Stuge]

Myles Watson wrote:
> > > Also, when booting Linux, the LED driver does not work with
> > > coreboot for me.
> >
> > The issue is that the driver is using a hard coded base address
> > rather than finding out what is actually programmed into the device,
> > and because coreboot doesn't assign resources exactly like the
> > factory BIOS, the driver can't find the hardware.
>
> Depending on the address, that could be easy to fix.  If it is
> below 0x1000 it is almost trivial.

It's at 6000 something, and I don't like to. I would much prefer the
driver not make assumptions for no da^Wreason.

//Peter

[Myles Watson]

On Wed, Sep 23, 2009 at 10:04 AM, Peter Stuge  wrote:
> Myles Watson wrote:
> > > > Also, when booting Linux, the LED driver does not work with
> > > > coreboot for me.
> > >
> > > The issue is that the driver is using a hard coded base address
> > > rather than finding out what is actually programmed into the device,
> > > and because coreboot doesn't assign resources exactly like the
> > > factory BIOS, the driver can't find the hardware.
> >
> > Depending on the address, that could be easy to fix.  If it is
> > below 0x1000 it is almost trivial.
>
> It's at 6000 something,

So that would be easy too.
> and I don't like to. I would much prefer the
> driver not make assumptions for no da^Wreason.

Agreed.  I guess it comes down to making changes where you can.  Have you
filed a bug report with the driver's authors?

Thanks,
Myles

[Ward Vandewege]

On Wed, Sep 23, 2009 at 06:04:57PM +0200, Peter Stuge wrote:
> Myles Watson wrote:
> > > > Also, when booting Linux, the LED driver does not work with
> > > > coreboot for me.
> > >
> > > The issue is that the driver is using a hard coded base address
> > > rather than finding out what is actually programmed into the device,
> > > and because coreboot doesn't assign resources exactly like the
> > > factory BIOS, the driver can't find the hardware.
> >
> > Depending on the address, that could be easy to fix.  If it is
> > below 0x1000 it is almost trivial.
>
> It's at 6000 something, and I don't like to. I would much prefer the
> driver not make assumptions for no da^Wreason.

I think the driver assumes

CS5536_BASE = 0x06100

Thanks,
Ward.

[Daniel Mack]

On Wed, Sep 23, 2009 at 06:04:57PM +0200, Peter Stuge wrote:
> Myles Watson wrote:
> > > > Also, when booting Linux, the LED driver does not work with
> > > > coreboot for me.
> > >
> > > The issue is that the driver is using a hard coded base address
> > > rather than finding out what is actually programmed into the device,
> > > and because coreboot doesn't assign resources exactly like the
> > > factory BIOS, the driver can't find the hardware.
> >
> > Depending on the address, that could be easy to fix.  If it is
> > below 0x1000 it is almost trivial.
>
> It's at 6000 something, and I don't like to. I would much prefer the
> driver not make assumptions for no da^Wreason.

Could you outline which steps would need to be taken in order to find
out the correct address to use? Any maybe a way to sany detect the
precence of that function on the board? I might go ahead and send a
patch for the driver then.

Thanks,
Daniel

[Tom Sylla]

On Wed, Sep 23, 2009 at 1:10 PM, Daniel Mack  wrote:
> Could you outline which steps would need to be taken in order to find
> out the correct address to use? Any maybe a way to sany detect the
> precence of that function on the board? I might go ahead and send a
> patch for the driver then.

Not really an outline; it is just one MSR read. Take a look at the
GPIO kernel driver:

http://lxr.linux.no/#linux+v2.6.31/drivers/char/cs5535_gpio.c#L188

Also, to correct the 0xF0000 scan ickiness, the proper way to detect a
board revision is usually done by reading a PCI subvendor/subdevice ID
too. I don't know if alix's non-coreboot BIOS does that properly.

[Daniel Mack]

On Wed, Sep 23, 2009 at 01:25:21PM -0400, Tom Sylla wrote:
> On Wed, Sep 23, 2009 at 1:10 PM, Daniel Mack  wrote:
> > Could you outline which steps would need to be taken in order to find
> > out the correct address to use? Any maybe a way to sany detect the
> > precence of that function on the board? I might go ahead and send a
> > patch for the driver then.
>
> Not really an outline; it is just one MSR read. Take a look at the
> GPIO kernel driver:
>
> http://lxr.linux.no/#linux+v2.6.31/drivers/char/cs5535_gpio.c#L188

One attempt to do that I just sumbitted to LKML:

http://lkml.org/lkml/2009/10/5/426

Works fine here - let's see what the maintainers say.

Thanks for the pointers,
Daniel

[Peter Stuge]

Daniel Mack wrote:
> http://lkml.org/lkml/2009/10/5/426
>
> Works fine here - let's see what the maintainers say.

gpio_base should maybe be 16 bit.

I'm not sure if strchr() can be assumed to work with '\0'.

//Peter