From: David Lechner <dlechner@baylibre.com>
Date: Thu, 19 Mar 2026 20:00:11 +0000 (-0500)
Subject: arm: mediatek: mt8188: fix gd->ram_top limit
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7518e10cd2352f9b2fd635c5077c070d3f3abfbd;p=thirdparty%2Fu-boot.git

arm: mediatek: mt8188: fix gd->ram_top limit

Fix the implementation of the gd->ram_top limit for mt8188.

The intention of the comment about MMC/DMA is correct, but the
implementation was wrong. gd->mon_len is set to the code size of U-Boot,
so trying to set it to limit gd->ram_top does not make sense.

Instead, there is already a get_effective_memsize() weak function that
we can override to implement the required limit on the usable memory
size. This is used to set gd->ram_top in setup_dest_addr().

The comment about the extra SZ_1M needing to be reserved is not correct
as U-Boot already takes care of this (with the actual size of U-Boot) in
the various board_f functions, so it is removed.

This fixes DMA not working on MMC on mt8188.

Reviewed-by: Julien Stephan <jstephan@baylibre.com>
Tested-by: Julien Stephan <jstephan@baylibre.com>
Link: https://patch.msgid.link/20260319-mtk-init-fix-dram-v1-8-6171ec141f40@baylibre.com
Signed-off-by: David Lechner <dlechner@baylibre.com>
---

diff --git a/arch/arm/mach-mediatek/mt8188/init.c b/arch/arm/mach-mediatek/mt8188/init.c
index fc80bc92bd8..a48a41f3b97 100644
--- a/arch/arm/mach-mediatek/mt8188/init.c
+++ b/arch/arm/mach-mediatek/mt8188/init.c
@@ -9,6 +9,7 @@
 #include <asm/global_data.h>
 #include <asm/system.h>
 #include <dm/uclass.h>
+#include <linux/kernel.h>
 #include <linux/sizes.h>
 #include <wdt.h>
 
@@ -16,23 +17,16 @@ DECLARE_GLOBAL_DATA_PTR;
 
 int dram_init(void)
 {
-	int ret;
-
-	ret = fdtdec_setup_mem_size_base();
-	if (ret)
-		return ret;
+	return fdtdec_setup_mem_size_base();
+}
 
+phys_size_t get_effective_memsize(void)
+{
 	/*
-	 * Limit gd->ram_top not exceeding SZ_4G.  Some periphals like mmc
-	 * requires DMA buffer allocated below SZ_4G.
-	 *
-	 * Note: SZ_1M is for adjusting gd->relocaddr, the reserved memory for
-	 * u-boot itself.
+	 * Limit gd->ram_top not exceeding SZ_4G. Because some peripherals like
+	 * MMC requires DMA buffer allocated below SZ_4G.
 	 */
-	if (gd->ram_base + gd->ram_size >= SZ_4G)
-		gd->mon_len = (gd->ram_base + gd->ram_size + SZ_1M) - SZ_4G;
-
-	return 0;
+	return min(SZ_4G - gd->ram_base, gd->ram_size);
 }
 
 void reset_cpu(void)