[PATCH 2/2] ARM: i.MX8M: esdctl: split memory banks for devices with >4G

Marco Felsch m.felsch at pengutronix.de
Thu Aug 31 06:05:49 PDT 2023

At the moment the whole available memory is added to one single memory
bank "ram0". This can cause barebox chainload issues on devices with a
huge amount of memory like the i.MX8MP-EVK which has 6G of RAM if the
barebox pbl binary is to large.

The reason for this issues is that memory_bank_first_find_space()
returns the memory area with the largest amount of free space on the
first memory bank. So in case of Debix SOM-A 8G and i.MX8MP-EVK 6G this
is the area crossing the 4G boundary. This cause the barebox pbl code to
trigger a MMU exception once the early MMU gets enabled which is
configured for sizes <=4G.

Split the memory space into two memory banks: "ram0" and "ram1" to fix
this issue.

Signed-off-by: Marco Felsch <m.felsch at pengutronix.de>
 arch/arm/mach-imx/esdctl.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/arch/arm/mach-imx/esdctl.c b/arch/arm/mach-imx/esdctl.c
index 54c62c47338e..de23b6433355 100644
--- a/arch/arm/mach-imx/esdctl.c
+++ b/arch/arm/mach-imx/esdctl.c
@@ -510,16 +510,26 @@ static resource_size_t imx8m_ddrc_sdram_size(void __iomem *ddrc, unsigned buswid
 				   reduced_adress_space, mstr);
+static int _imx8m_ddrc_add_mem(void *mmdcbase, struct imx_esdctl_data *data,
+			       unsigned int buswidth)
+	resource_size_t size = imx8m_ddrc_sdram_size(mmdcbase, buswidth);
+	resource_size_t size0, size1;
+	size0 = min_t(resource_size_t, SZ_4G - MX8M_DDR_CSD1_BASE_ADDR, size);
+	size1 = size - size0;
+	return add_mem(data->base0, size0, SZ_4G, size1, true);
 static int imx8m_ddrc_add_mem(void *mmdcbase, struct imx_esdctl_data *data)
-	return arm_add_mem_device("ram0", data->base0,
-			   imx8m_ddrc_sdram_size(mmdcbase, 32));
+	return _imx8m_ddrc_add_mem(mmdcbase, data, 32);
 static int imx8mn_ddrc_add_mem(void *mmdcbase, struct imx_esdctl_data *data)
-	return arm_add_mem_device("ram0", data->base0,
-			   imx8m_ddrc_sdram_size(mmdcbase, 16));
+	return _imx8m_ddrc_add_mem(mmdcbase, data, 16);
 static resource_size_t imx7d_ddrc_sdram_size(void __iomem *ddrc)

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