Linux/AM5728: Enabling DCACHE in u-boot

Michael,

Michael Shklyarman said:

The issue is that I do NOT see the CONFIG_SYS_DCACHE_OFF flag being set in standard SDK uboot build environment. This means that the dcache_enable() should be executed

Michael Shklyarman said:

After building uboot I grepped the whole uboot tree for CONFIG_SYS_DCACHE_OFF and it is not found in any build configuration or .h files.

Yes, I also think that this flag CONFIG_SYS_DCACHE_OFF is NOT set in the default PSDK. In PSDK 5.01 AM572x EVM u-boot prompt, when I execute below command I have an output indicating that dcache is being enabled:

=> bdinfo
arch_number = 0x00000000
boot_params = 0x80000100
DRAM bank   = 0x00000000
-> start    = 0x80000000
-> size     = 0x80000000
baudrate    = 115200 bps
TLB addr    = 0xFFFF0000
relocaddr   = 0xFFF4F000
reloc off   = 0x7F74F000
irq_sp      = 0xFDF15D40
sp start    = 0xFDF15D30
Early malloc usage: 700 / 2000
fdt_blob = fdf15d58

u-boot/cmd/bdinfo.c

#if !(defined(CONFIG_SYS_ICACHE_OFF) && defined(CONFIG_SYS_DCACHE_OFF))
    print_num("TLB addr", gd->arch.tlb_addr);
#endif

If you need to set this flag, this should be done in u-boot/include/configs/am57xx_evm.h file, like for example in below file:

u-boot/include/configs/ti_armv7_keystone2.h:    #define CONFIG_SYS_DCACHE_OFF

Michael Shklyarman said:

This means that the dcache_enable() should be executed and yet the C bit in the SCTRL registers shows 0 when I connect with debugger. Am I missing something?

I can think of two possible issue:

1. How exactly you check SCTRL register? At which point exactly? May be you are checking the wrong register or checking too early. See if you are aligned with below e2e post:

2. dcache might be disabled after being enabled. You can trace below source code and check (with printf or breakpoints) if dcache_disable() code is being executed:

u-boot/common/spl/spl.c

void board_init_r(gd_t *dummy1, ulong dummy2)
{

#if !(defined(CONFIG_SYS_ICACHE_OFF) && defined(CONFIG_SYS_DCACHE_OFF)) && \
        defined(CONFIG_ARM)
    cleanup_before_linux();
#endif

}

u-boot/arch/arm/cpu/armv7/cpu.c

int cleanup_before_linux_select(int flags)
{

dcache_disable()

}

u-boot/doc/README.arm-caches

Cleanup Before Linux:
- cleanup_before_linux() should flush the D-cache, invalidate I-cache, and
  disable MMU and caches.
- The following sequence is advisable while disabling d-cache:
  1. dcache_disable() - flushes and disables d-cache
  2. invalidate_dcache_all() - invalid any entry that came to the cache in the short period after the cache was flushed but before the cache got disabled.

Regards,
Pavel