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

[Peng Fan]

> 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 at 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 at 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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