linux driver, port 2.6.19.2 - 2.6.38-rc2 ARM11 iMX31, amba MBX device LogicPD Litekit GLES driver - linux-kernel

Question

Code followed with question
#define MBX_REG_SYS_PHYS_BASE 0xC0000000
#define MBX_REG_RANGE 0x00004000
static struct resource mxc_reg_resources[] = {
{
.start = MBX_REG_SYS_PHYS_BASE,
.end = MBX_REG_SYS_PHYS_BASE + MBX_REG_RANGE - 1,
.flags = IORESOURCE_MEM }
};
mbx_reg = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!mbx_reg)
return -EINVAL;
reg_base = ioremap(mbx_reg->start, resource_size(mbx_reg));
if (!reg_base) {
ret = -ENOMEM;
goto eremap;
}
printk(KERN_CRIT "Address: from 0x%08X to 0x%08X\n",
mbx_reg->start, reg_base);
regread = mx3reg_read_reg(mx3reg, MBX1_GLOBREG_REVISION);
printk(KERN_CRIT "MBX1_GLOBREG_REVISION: 0x%.8X\n", regread);
This code works on iMX31 from LogicPD using 2.6.19.2 with out of tree patching from freescale.
when porting it to 2.6.38-rc2 it no longer works.
here are some data results:
Working results:
Address: 0xC7860000
MBX1_GLOBREG_REVISION: 0x01010200
Failed results:
Address: 0xC48A0000
MBX1_GLOBREG_REVISION: 0x00000000
Address: 0xC48A8000
MBX1_GLOBREG_REVISION: 0x00000000
Address: 0xC48B8000
MBX1_GLOBREG_REVISION: 0x00000000
Address: 0xC48C0000
MBX1_GLOBREG_REVISION: 0x00000000
maybe interesting is on 2.6.19.2 it always gets the same address mapped
yet in 2.6.38-rc2 it does not.

Answer 1

Are you sure your defines are still good ? The output for this line should not change :
printk(KERN_CRIT "Address: from 0x%08X to 0x%08X\n",
mbx_reg->start, reg_base);
Since it is a physical address. However it is not printed in your output.
Check the pripheral you are accessing is clocked.

Answer 2

In order to have this device ready to communicate you need to setup the peripheral port remap register
/* Setup Peripheral Port Remap register for AVIC */
asm("ldr r0, =0xC0000015 \n\
mcr p15, 0, r0, c15, c2, 4");
here is the code from the original 2.6.19.2 kernel, executed from a board fixup routine.
and of course the clocks would have to be enabled as well, and this driver example is not showing that either.