[U-Boot] [RFC PATCH v2] ARM: Avoid compiler optimization for usages of readb, writeb and friends.

[Alexander Holler <holler@ahsoftware.de>]

Am 19.12.2010 19:45, schrieb John Rigby:
> On Sun, Dec 19, 2010 at 3:22 AM, Alexander Holler<holler@ahsoftware.de>  wrote:
>> side effects here. Reading NAND now fails on my BeagleBoard. Regardless
>> if I use gcc 4.3.5 or gcc 4.5.1, after applying that patch the wrong ID
>> of the NAND is read. In nand_get_flash_type()
>> (drivers/mtd/nand/nand_base.c) without that patch I will get the following:
>>
>> *maf_id: 44, dev_id: 186
>>
>> with the patch the following is read:
>>
>> *maf_id: 128, dev_id: 85
> The nand_get_flash_type routine reads these id's twice and compares
> them.  Do your see an error message like this?
>
> second ID read did not match
>

No, the output is

without memory barrier in read*/write*:
--------------------------------
U-Boot 2010.12-rc3-00013-g71aab09 (Dec 19 2010 - 01:19:38)

OMAP3530-GP ES3.1, CPU-OPP2, L3-165MHz, Max CPU Clock 720 mHz
OMAP3 Beagle board + LPDDR/NAND
I2C:   ready
DRAM:  256 MiB
NAND:  256 MiB
MMC:   OMAP SD/MMC: 0
In:    serial
Out:   serial
Err:   serial
Beagle Rev C4
timed out in wait_for_pin: I2C_STAT=0
No EEPROM on expansion board
Die ID #062a000400000000040365fa16019019
Hit any key to stop autoboot:  0
OMAP3 beagleboard.org # nand info

Device 0: nand0, sector size 128 KiB
--------------------------------

with memory barrier in read*/write*:
--------------------------------
U-Boot 2010.12-rc3-00014-gde0126f (Dec 19 2010 - 01:25:11)

OMAP3530-GP ES3.1, CPU-OPP2, L3-165MHz, Max CPU Clock 720 mHz
OMAP3 Beagle board + LPDDR/NAND
I2C:   ready
DRAM:  256 MiB
NAND:  32 MiB
MMC:   OMAP SD/MMC: 0
NAND read from offset 260000 failed -74
*** Warning - readenv() failed, using default environment

In:    serial
Out:   serial
Err:   serial
Beagle Rev C4
timed out in wait_for_pin: I2C_STAT=0
No EEPROM on expansion board
Die ID #062a000400000000040365fa16019019
Hit any key to stop autoboot:  0
OMAP3 beagleboard.org # nand info

Device 0: nand0, sector size 16 KiB
--------------------------------

And with the memory barrier the kernel gets started but hangs afterwards 
(at least it looks so). I still haven't searched further and can only 
offer speculations like clocks are screwed up, memory setup is broken or 
such. Finding the reason and not just the impact will need some more 
time on my side.

Regards,

Alexander