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https://github.com/brain-hackers/u-boot-brain
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9abda6ba73
This patch fixes a problem on systems where the NOR flash is attached to a 64 bit bus. The toggle bit detection in flash_toggle() is based on the assumption that the same flash address is read twice without any other interjacent flash accesses. However, on 32 bit systems the function flash_read64() [as currently implemented] does not perform an atomic 64 bit read - instead, this is broken down into two 32 bit read accesses on addresses "addr" and "addr + 4". So instead of reading a 64 bit value twice from "addr", we see a sequence of 4 32 bit reads from "addr", "addr + 4", "addr", and "addr + 4". The consequence is that flash_toggle() fails to work. This patch implements a simple, but somewhat ugly solution, as it avoids the use of flash_read64() in this critical place (by breaking it down manually into 32 bit read operations) instead of rewriting flash_read64() such to perform atomic 64 bit reads as one could expect. However, such a rewrite would require the use of floating point load operations, which becomes pretty complex: save MSR; set Floating Point Enable bit in MSR; use "lfd" instruction to perform atomic 64 bit read; use "stfd" to store value to temporary variable on stack; load u64 value from temporary variable; restore saved MSR; return u64 value; The benefit-cost ratio of such an implementation was considered too bad to actually attempt this, especially as we can expect that such an implementation would not only have a bigger memory footprint but also cause a performance degradation. Signed-off-by: Wolfgang Denk <wd@denx.de> Signed-off-by: Stefan Roese <sr@denx.de> |
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| bios_emulator | ||
| block | ||
| dma | ||
| hwmon | ||
| i2c | ||
| input | ||
| misc | ||
| mmc | ||
| mtd | ||
| net | ||
| pci | ||
| pcmcia | ||
| qe | ||
| rtc | ||
| serial | ||
| spi | ||
| usb | ||
| video | ||