Subject: Re: [PATCH V2] cpu: imx8_cpu: Avoid revision to corrupt device tree

Hi,

On Thu, 17 Oct 2024 16:12:36 +0800 Peng Fan (OSS) wrote:

...

From: Peng Fan peng.fan@nxp.com

U-Boot device tree is padded just after U-Boot proper. After the whole stuff loaded to DRAM space, the device tree area is conflict with BSS region before U-Boot relocation.

So any write to BSS area before reloc_fdt will corrupt the device tree. Without the fix, there is issue that "binman_init failed:-2" on i.MX8MP-EVK board.

Placing the 'revision' variable into the 'data' section would achieve the same goal without any further code change: static char revision[4] __section(".data");

This was not welcomed, https://lore.kernel.org/all/20241017034507.GJ4959@bill-the-cat/

Regards, Peng.

...

Signed-off-by: Peng Fan peng.fan@nxp.com

V2: move the rev to malloc area in cpu_imx_plat tested on i.MX8MP

EVK

...

drivers/cpu/imx8_cpu.c | 35 ++++++++++++++++++++--------------- 1 file changed, 20 insertions(+), 15 deletions(-)

diff --git a/drivers/cpu/imx8_cpu.c b/drivers/cpu/imx8_cpu.c index 6c0a8c0cbe4..b11f8dc0c91 100644 --- a/drivers/cpu/imx8_cpu.c +++ b/drivers/cpu/imx8_cpu.c @@ -20,10 +20,11 @@

DECLARE_GLOBAL_DATA_PTR;

+#define IMX_REV_LEN 4 struct cpu_imx_plat { const char *name;

• const char *rev; const char *type;

• char rev[IMX_REV_LEN]; u32 cpu_rsrc; u32 cpurev; u32 freq_mhz;

@@ -69,28 +70,32 @@ static const char *get_imx_type_str(u32

imxtype)

...

} }

-static const char *get_imx_rev_str(u32 rev) +static void get_imx_rev_str(struct cpu_imx_plat *plat, u32 rev) {

• static char revision[4];
• if (IS_ENABLED(CONFIG_IMX8)) {

• char rev;
  

• switch (rev) { case CHIP_REV_A:

• 	return "A";
  

• 	rev = 'A';
  

• 	break;
  

  case CHIP_REV_B:

• 	return "B";
  

• 	rev = 'B';
  

• 	break;
  

  case CHIP_REV_C:

• 	return "C";
  

• 	rev = 'C';
  

• 	break;
  

  default:

• 	return "?";
  

• 	rev = '?';
  

• 	break;
  

  }

• plat->rev[0] = rev;
  

• plat->rev[1] = '\0';
  

  } else {

• revision[0] = '1' + (((rev & 0xf0) - CHIP_REV_1_0) >> 4);
  

• revision[1] = '.';
  

• revision[2] = '0' + (rev & 0xf);
  

• revision[3] = '\0';
  

• return revision;
  

• plat->rev[0] = '1' + (((rev & 0xf0) - CHIP_REV_1_0) >>
  

4);

...

• plat->rev[1] = '.';
  

• plat->rev[2] = '0' + (rev & 0xf);
  

• plat->rev[3] = '\0';
  

  }

}

@@ -318,7 +323,7 @@ static int imx_cpu_probe(struct udevice *dev) set_core_data(dev); cpurev = get_cpu_rev(); plat->cpurev = cpurev;

• plat->rev = get_imx_rev_str(cpurev & 0xFFF);

• get_imx_rev_str(plat, cpurev & 0xFFF); plat->type = get_imx_type_str((cpurev & 0x1FF000) >> 12); plat->freq_mhz = imx_get_cpu_rate(dev) / 1000000; plat->mpidr = dev_read_addr(dev);

Lothar Waßmann

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