Booting mx25 based device from SD and NOR

Fri May 25 05:04:52 EDT 2012

Hi Eric

> > well NAND boot + nand rootfs works fine here (cpuimx25) and I assume
> > > NAND boot + sd rootfs would work as sd is properly detected during
> boot.
> > >
> > > Yep, I believe it's more a question of me setting the parameters
> correctly
> > upon boot. But without a proper low level init (which I don't have
> because
> > I do not really understand all the details of the low level code), there
> > are other factors which could inhibit the proper boot, as you mention
> below.
> >
> if your sd's partitions are detected by the kernel you must be able to
> boot a rootfs on it it's just a bootargs problem (and kernel
> configuration to have the right FS included).
>

That's my understanding too, however it does not work at the moment. But
what's really important is that I have NOR support when loading barebox as
first stage boot loader from SD card.


> > I suppose WEIM configuration is done in the low level part, isn't it?
> Where
> > would I find an appropriate example? I have been reading all the fsl
> > board's low_level codes, but have a hard time figuring out how to apply
> it
> > to my board.
> >
> > With regard to the IOMUX, I was under the impression that it does not
> > matter much, since after low level code run, the execution path is:
> >
> >         late_initcall()
> >         mem_initcall()
> >         device_initcall() --> add_cfi_flash_device()
> >         console_initcall() --> mxc_iomux_v3_setup_multiple_pads()
> >         core_initcall()
> >
> > So CFI/NOR detection happens before IOMUX setup, at least that's what I
> > have gathered for my board copying from various other examples in
> barebox.
> > What would the correct code execution path be from the architectural
> point
> > of view?
> >
> nothing prevents you from moving mxc_iomux_v3_setup_multiple_pads to
> device_initcall as done in
>
> http://git.pengutronix.de/?p=barebox.git;a=blob;f=arch/arm/boards/eukrea_cpuimx25/eukrea_cpuimx25.c;h=1b8f618138023b88893a024ddc0c078b7b9f2325;hb=c48de4beee21c3a5573cec084123c33ae08f6f7a
>
> Thanks, I have done this now, looks much cleaner. Stil, I wonder about the
order of things when powering and booting up the mx25 in general.

        lowlevel -> AIPS -> MAX (MPR, SGPCR, MGPCR) -> M3IF -> MPLL clock
-> other clocks
        late_initcall -> fec_init
        mem_initcall -> imx25_mem_init
        device_initcall -> devices_init
        console_initcall -> console_init
        core_initcall -> core_setup


> for the weim setting you may need to do something similar to what is
> done on line 187 of :
>
> http://git.pengutronix.de/?p=barebox.git;a=blob;f=arch/arm/boards/eukrea_cpuimx27/eukrea_cpuimx27.c;h=63e87c9551c440edab572f5252a503ba4d533161;hb=c48de4beee21c3a5573cec084123c33ae08f6f7a
>
>
Now that piece certainly was missing, but how the heck did you find out
those register values? Where did you get the information about writing to
chip select 0 and selecting:

CSCR0U: 0x00008F03
CSCR0L: 0xA0330D01
CSCR0A: 0x002208C0

I have patched mx25-regs.h accordingly and added an equivalent call using
the same register values:

diff --git a/arch/arm/mach-imx/include/mach/imx25-regs.h
b/arch/arm/mach-imx/include/mach/imx25-regs.h
index 73307c4..8225832 100644
--- a/arch/arm/mach-imx/include/mach/imx25-regs.h
+++ b/arch/arm/mach-imx/include/mach/imx25-regs.h
@@ -72,6 +72,7 @@
 #define CCM_LTR1 0x44
 #define CCM_LTR2 0x48
 #define CCM_LTR3 0x4c
+#define CCM_MCR 0x64

 #define PDR0_AUTO_MUX_DIV(x) (((x) & 0x7) << 9)
 #define PDR0_CCM_PER_AHB(x) (((x) & 0x7) << 12)
@@ -107,6 +108,22 @@
 #define CSCR_L(x)     (WEIM_BASE + 4 + (x) * 0x10)
 #define CSCR_A(x)     (WEIM_BASE + 8 + (x) * 0x10)

+/* Chip Select Registers */
+#define IMX_WEIM_BASE WEIM_BASE
+#define CSxU(x) __REG(IMX_WEIM_BASE + (cs * 0x10) + 0x00) /* Chip Select x
Upper Register    */
+#define CSxL(x) __REG(IMX_WEIM_BASE + (cs * 0x10) + 0x04) /* Chip Select x
Lower Register    */
+#define CSxA(x) __REG(IMX_WEIM_BASE + (cs * 0x10) + 0x08) /* Chip Select x
Addition Register */
+#define EIM  __REG(IMX_WEIM_BASE + 0x60) /* WEIM Configuration Register
  */
+
+#ifndef __ASSEMBLY__
+static inline void imx25_setup_weimcs(size_t cs, unsigned upper, unsigned
lower, unsigned addional)
+{
+        CSxU(cs) = upper;
+        CSxL(cs) = lower;
+        CSxA(cs) = addional;
+}
+#endif /* __ASSEMBLY__ */
+
 /*
  * Definitions for the clocksource driver
  *

But it still does not work. What could be missing? How can I find out more
about which chip select I need? I'm practically married to the MX25-RM
documentation, but still, it's one heck of a large piece of documentation.
I found the following example (using cs2), but I am not sure this helps:

@; config WEIM to Async access with EDC, OEA, RWA, RWN, EBC, 16 bit port
and PSR WRITE WEIM_CSCR2U, 0x12020802

WRITE WEIM_CSCR2L, 0x80330d03

@ ; config Flash to WRAP 8 mode (by half word accesses) WRITE_H
(CS2_BASE_ADDR+0x2384), 0x60 @ ; offset = 0x11c2 << 1 for 16 bit port
WRITE_H (CS2_BASE_ADDR+0x2384), 0x03

WRITE_H (CS2_BASE_ADDR+0x0), 0xff @ ; Flash to read mode

@ ; config to WEIM Sync access with WRAP8, 16 bit port WRITE WEIM_CSCR2U,
0x13510802
WRITE WEIM_CSCR2L, 0x80330d03

Could it be that I am missing an iomux setting? Clock missing? I am fairly
certain that my NOR is at CS0, so the above example from the RM does not
help much, I suppose.

Best regards
Roberto
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