problem with xsysace

From: Petr Cvek
Date: Thu Oct 06 2011 - 06:45:40 EST

I'm using microblaze arch 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` xs`1 xs`2)

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. This is because type of value, which is unsigned (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.;a=commitdiff;h=5d10302f46df1d9a85c34ea97f9b6c29e414482e

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

diff --git a/drivers/block/xsysace.c b/drivers/block/xsysace.c
index fb1975d..3ed920c 100644
--- a/drivers/block/xsysace.c
+++ b/drivers/block/xsysace.c
@@ -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;

Signed-off-by: Petr Cvek <petr.cvek@xxxxxx>
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