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rk27xx: Use slower memory timings at startup

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Our decade+old defaults are reported to trigger a failure on
one user's IHIFI770c and IHIFI960, but work on their HM-603.
Backing CAS latency off from 2 to 3 appears to be sufficient.

What's interesting is that on paper, CL=2 should be easily attainable
due to our max RAM clock of 100MHz, well within the worst-case timings
of the EM639165 SDRAM.

So as an experiment, this code can go back to CL=2 when we change the
CPU+RAM clock speeds.  IF this still proves problematic, it will be
removed.

Change-Id: I4a8cfa0563c076e7f25d9599a19b454f590861cd
This commit is contained in:
Solomon Peachy 2025-11-28 07:08:28 -05:00
parent 3307b04eed
commit a6538abd16
1 changed files with 19 additions and 5 deletions
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24
firmware/target/arm/rk27xx/system-rk27xx.c
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@ -90,10 +90,10 @@ static void UIRQ(void)
void irq_handler(void)
{
asm volatile("stmfd sp!, {r0-r5, ip, lr} \n" /* store context */
"ldr r4, =0x18080000 \n" /* INTC base */
"ldr r4, =0x18080000 \n" /* INTC base */
"ldr r5, [r4, #0x104] \n" /* INTC_ISR */
"and r5, r5, #0x1f \n" /* irq_no = INTC_ISR & 0x1f */
"ldr r3, =irqvector \n"
"ldr r3, =irqvector \n"
"ldr r3,[r3, r5, lsl #2] \n"
"blx r3 \n" /* irqvector[irq_no]() */
"mov r3, #1 \n"
@ -117,8 +117,14 @@ void system_init(void)
WDTCON &= ~(1<<3);
#ifndef BOOTLOADER
/* SDRAM tweaks */
MCSDR_MODE = (2<<4)|3; /* CAS=2, burst=8 */
/* SDRAM tweaks. Note this assumes 100MHz AHB+SDRAM clock. */
#if !(defined(HM60X) || defined(HM801))
MCSDR_MODE = (3<<4)|3; /* CAS=3, burst=8(2^3) -- Safe but slower */
#else
MCSDR_MODE = (2<<4)|3; /* CAS=2, burst=8(2^3) -- Ideal but causes startup issues on (some?) IHIFI devices */
#endif
MCSDR_T_REF = (125*100) >> 3; /* 125/8 = 15.625 autorefresh interval */
MCSDR_T_RFC = (64*100) / 1000; /* autorefresh period */
MCSDR_T_RP = 1; /* precharge period */
@ -232,9 +238,15 @@ void commit_discard_dcache_range (const void *base, unsigned int size)
}
}
#ifdef HAVE_ADJUSTABLE_CPU_FREQ
#if !defined(BOOTLOADER) && defined(HAVE_ADJUSTABLE_CPU_FREQ)
static inline void set_sdram_timing(int ahb_freq)
{
#if 1
if (ahb_freq > 100000000)
MCSDR_MODE = (3<<4)|3; /* CAS=3, burst=8(2^3) */
else
MCSDR_MODE = (2<<4)|3; /* CAS=2, burst=8(2^3) */
#endif
MCSDR_T_REF = (125*ahb_freq/1000000) >> 3;
MCSDR_T_RFC = (64*ahb_freq/1000000)/1000;
}
@ -244,6 +256,8 @@ void set_cpu_frequency(long frequency)
if (cpu_frequency == frequency)
return;
/* Temporarily use more conservative SDRAM settings
so we don't glitch when changing clocks */
set_sdram_timing(12000000);
if (frequency == CPUFREQ_MAX)