[参考译文] AM62L-PROCESSOR-SDK：自适应 LPDDR4 容量

我们也尝试过一种方法,但我们不确定它是否是最好的。 附件是修订后的 board/ti/common/k3-DDR。

// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2024, Texas Instruments Incorporated - https://www.ti.com/
 */

#include <fdt_support.h>
#include <dm/uclass.h>
#include <k3-ddrss.h>
#include <spl.h>
#include <linux/sizes.h>
#include <asm/io.h>

#include "k3-ddr.h"

DECLARE_GLOBAL_DATA_PTR;

#ifdef CONFIG_TARGET_AM62L3_EVM
/* DDR auto-detection for AM62LX platforms (1GB/2GB only) */
#define DDR_BASE_ADDR		0x80000000UL
#define DDR_TEST_PATTERN1	0x5A5A5A5A
#define DDR_TEST_PATTERN2	0xA5A5A5A5

/**
 * ddr_memory_test() - Test if memory address is accessible
 * @addr: Address to test
 * 
 * Returns: 1 if accessible, 0 if not
 */
static int ddr_memory_test(ulong addr)
{
	volatile u32 *test_addr = (volatile u32 *)addr;
	u32 original_value;
	int result = 0;

	/* Save original value */
	original_value = *test_addr;

	/* Test pattern 1 */
	*test_addr = DDR_TEST_PATTERN1;
	if (*test_addr == DDR_TEST_PATTERN1) {
		/* Test pattern 2 */
		*test_addr = DDR_TEST_PATTERN2;
		if (*test_addr == DDR_TEST_PATTERN2) {
			result = 1;
		}
	}

	/* Restore original value */
	*test_addr = original_value;

	return result;
}

/**
 * detect_ddr_size() - Auto-detect DDR memory size (1GB or 2GB)
 * 
 * Returns: Detected DDR size in bytes, 0 if detection failed
 */
static phys_size_t detect_ddr_size(void)
{
	ulong test_addr_1gb, test_addr_2gb;
	phys_size_t detected_size = 0;

	debug("DDR:   Auto-detecting memory size (1GB/2GB)...\n");

	/* Test 1GB boundary */
	test_addr_1gb = DDR_BASE_ADDR + SZ_1G - 4;
	
	/* Test 2GB boundary */
	test_addr_2gb = DDR_BASE_ADDR + SZ_2G - 4;

	if (ddr_memory_test(test_addr_2gb)) {
		/* 2GB is accessible */
		detected_size = SZ_2G;
#ifndef CONFIG_SPL_BUILD
		printf("DDR:   Auto-detected 2GiB\n");
#endif
	} else if (ddr_memory_test(test_addr_1gb)) {
		/* Only 1GB is accessible */
		detected_size = SZ_1G;
#ifndef CONFIG_SPL_BUILD
		printf("DDR:   Auto-detected 1GiB\n");
#endif
	} else {
#ifndef CONFIG_SPL_BUILD
		printf("DDR:   Detection failed, using default\n");
#endif
		/* Use device tree default if detection fails */
		detected_size = gd->ram_size;
	}

	return detected_size;
}
#endif /* CONFIG_TARGET_AM62L3_EVM */

int dram_init(void)
{
	s32 ret;

	ret = fdtdec_setup_mem_size_base_lowest();
	if (ret) {
		printf("Error setting up mem size and base. %d\n", ret);
		return ret;
	}

#ifdef CONFIG_TARGET_AM62L3_EVM
	/* Auto-detect DDR size for AM62LX (1GB/2GB) */
	phys_size_t detected_size = detect_ddr_size();
	
	/* Update global data with detected size */
	if (detected_size > 0) {
		gd->ram_size = detected_size;
		debug("DDR: Updated ram_size to %llu bytes\n", gd->ram_size);
	}
#endif

	return 0;
}

int dram_init_banksize(void)
{
	s32 ret;

#ifdef CONFIG_TARGET_AM62L3_EVM
	/* For AM62LX with auto-detection, set up banks based on detected size */
	gd->bd->bi_dram[0].start = DDR_BASE_ADDR;
	gd->bd->bi_dram[0].size = gd->ram_size;
	
	/* Clear remaining banks */
	for (int i = 1; i < CONFIG_NR_DRAM_BANKS; i++) {
		gd->bd->bi_dram[i].start = 0;
		gd->bd->bi_dram[i].size = 0;
	}
	
	debug("DDR: Bank 0: start=0x%llx, size=0x%llx\n", 
	      gd->bd->bi_dram[0].start, gd->bd->bi_dram[0].size);
	ret = 0;
#else
	/* Use standard setup for other K3 platforms */
	ret = fdtdec_setup_memory_banksize();
	if (ret)
		printf("Error setting up memory banksize. %d\n", ret);
#endif

	return ret;
}