System ACE fails in look for root devices

Hello,

I sent this mail some time ago, but nobody replied :-(.

I'm using microblaze linux on ML506 board and I found problem with SystemACE CF driver.

When xsysace driver is probed, and dts file does not include entry "port-number" (existence of line not actually tested) on line:

	of_property_read_u32(dev->dev.of_node, "port-number", &id);

kernel fails to boot with this message:

<4>VFS: Cannot open root device "xsa2" or unknown-block(0,0) <4>Please append a correct "root=" boot option; here are the available
partitions:

	<4>fff:ffff0     990864 xs`  (driver?)
	<4>  fff:ffff1     124960 xs`1 00000000-0000-0000-0000-000000000000
	<4>  fff:ffff2     865872 xs`2 00000000-0000-0000-0000-000000000000
	<0>Kernel panic - not syncing: VFS: Unable to mount root fs on  

unknown-block(0,0)

(note xs xs1 xs`2 partition names)

So I've done some searching and found "ace->id" variable, which has value "-1". Because this value define letter of drive and is incremented by 'a', then with its value of -1, creates letter before 'a' thus '`'.

"ace->id" value is assigned in ace_probe function on line

      of_property_read_u32(dev->dev.of_node, "port-number", &id);
      if (id < 0)
          id = 0;

This condition should prevents value to be less than zero, but is does not. It's because type, which is u32 few lines before, condition is never true. So I suggest changing it to int. Actually, there was patch some time ago, which has changed it into u32 (last patch for xsysace.c).

	http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=5d10302f46df1d9a85c34ea97f9b6c29e414482e

And finally here is my patch, which suggests changing this line back:

Test for signed value is never true, because of unsigned type.

From: Petr Cvek <[email protected]>

---

index fb1975d..3ed920c 100644
@@ -1155,7 +1155,7 @@ static int __devinit ace_probe(struct

platform_device *dev)
{
resource_size_t physaddr = 0;
int bus_width = ACE_BUS_WIDTH_16; /* FIXME: should not be hard
coded */
- u32 id = dev->id;

+       int id = dev->id;
          int irq = NO_IRQ;
          int i;

However, of_property_read_u32() can only accept a u32 value, not an int, so this needs to be solved with two variables to be correct:

	int id;
	u32 tmp;
	id = dev->id;
	if (of_property_read_u32(dev->dev.of_node, "port-number", &tmp)
		id = tmp;
	if (id < 0)
		id = 0;

It's not as pretty, but it is a limitation of how of_property_read_u32 has to be implemented. I hope to find a better way to do it that doesn't have the u32 restriction on the return value.

g.

Sorry for delay. I had lot of work.

I think of_property_read_u32() returns nonzero, when not found (-ENODATA), therefore:

	if (! of_property_read_u32(dev->dev.of_node, "port-number", &tmp))

I hope, nobody will use port-number bigger than max(int) :-D. Oh and I would improve code to something like this:

	int id;
	u32 tmp;
	if (! of_property_read_u32(dev->dev.of_node, "port-number", &tmp))  
{	/*when return 0, use tmp val*/
	  id = tmp;			/*always >0 */
	} else {			/* when error, use dev->id and test >0 */
	  id = dev->id;
	  if (id < 0)
	    id = 0;
	}

Petr