[PATCH] ARM: mx6: Add function to read UNIQUE_ID

[Tom Rini]

On Thu, Feb 04, 2021 at 10:41:20PM +0100, Heinrich Schuchardt wrote:
> On 2/4/21 9:52 PM, Sean Anderson wrote:
> > 
> > 
> > On 2/4/21 3:41 PM, Tom Rini wrote:
> >  > On Thu, Feb 04, 2021 at 03:29:48PM -0500, Sean Anderson wrote:
> >  >
> >  >> This is almost identical to the imx7 version, except that the register
> >  >> names are different.
> >  >>
> >  >> Signed-off-by: Sean Anderson <sean.anderson at seco.com>
> >  >> ---
> >  >>
> >  >>   arch/arm/mach-imx/mx6/soc.c | 33 +++++++++++++++++++++++++++++++++
> >  >>   1 file changed, 33 insertions(+)
> >  >>
> >  >> diff --git a/arch/arm/mach-imx/mx6/soc.c b/arch/arm/mach-imx/mx6/soc.c
> >  >> index bf6dddfdc9..cb729be46f 100644
> >  >> --- a/arch/arm/mach-imx/mx6/soc.c
> >  >> +++ b/arch/arm/mach-imx/mx6/soc.c
> >  >> @@ -11,6 +11,7 @@
> >  >>   #include <linux/delay.h>
> >  >>   #include <linux/errno.h>
> >  >>   #include <asm/io.h>
> >  >> +#include <asm/setup.h>
> >  >>   #include <asm/arch/imx-regs.h>
> >  >>   #include <asm/arch/clock.h>
> >  >>   #include <asm/arch/sys_proto.h>
> >  >> @@ -705,6 +706,38 @@ int arch_misc_init(void)
> >  >>   }
> >  >>   #endif
> >  >>
> >  >> +#ifdef CONFIG_SERIAL_TAG
> >  >> +/*
> >  >> + * UNIQUE_ID describes a unique ID based on silicon wafer
> >  >> + * and die X/Y position
> >  >> + *
> >  >> + * UNIQUE_ID offset 0x410
> >  >> + * 31:0 fuse 0
> >  >> + * FSL-wide unique, encoded LOT ID STD II/SJC CHALLENGE/ Unique ID
> >  >> + *
> >  >> + * UNIQUE_ID offset 0x420
> >  >> + * 31:24 fuse 1
> >  >> + * The X-coordinate of the die location on the wafer/SJC CHALLENGE/
> > Unique ID
> >  >> + * 23:16 fuse 1
> >  >> + * The Y-coordinate of the die location on the wafer/SJC CHALLENGE/
> > Unique ID
> >  >> + * 15:11 fuse 1
> >  >> + * The wafer number of the wafer on which the device was
> > fabricated/SJC
> >  >> + * CHALLENGE/ Unique ID
> >  >> + * 10:0 fuse 1
> >  >> + * FSL-wide unique, encoded LOT ID STD II/SJC CHALLENGE/ Unique ID
> >  >> + */
> >  >> +void get_board_serial(struct tag_serialnr *serialnr)
> >  >> +{
> >  >> +    struct ocotp_regs *ocotp = (struct ocotp_regs *)OCOTP_BASE_ADDR;
> >  >> +    struct fuse_bank *bank = &ocotp->bank[0];
> >  >> +    struct fuse_bank0_regs *fuse =
> >  >> +        (struct fuse_bank0_regs *)bank->fuse_regs;
> >  >> +
> >  >> +    serialnr->low = fuse->uid_low;
> >  >> +    serialnr->high = fuse->uid_high;
> >  >> +}
> >  >> +#endif
> >  >> +
> >  >>   /*
> >  >>    * gpr_init() function is common for boards using MX6S, MX6DL, MX6D,
> >  >>    * MX6Q and MX6QP processors
> >  >
> >  > NAK.  This needs to use the normal mechanism to populate "serial#"
> >  > directly and not abuse the old ATAG infrastructure.
> > 
> > What is the "normal" mechanism? Define something like
> > omap_die_id_serial which sets serial# directly? From what I can tell,
> > get_board_serial is the "generic" function for separating the getting of
> > the serial from the setting of serial#.
> > 
> > --Sean
> 
> get_board_serial() is defined as empty function in bootm.h if
> CONFIG_SERIAL_TAG=n. But CONFIG_SERIAL_TAG is not documented anywhere.

Correct, it's ATAGs related stuff, so quite old and at best may have
been documented in the README at some point.

> board/gateworks/gw_ventana/gw_ventana.c has this comment:
> 
> #ifdef CONFIG_SERIAL_TAG
> /*
>  * called when setting up ATAGS before booting kernel
>  * populate serialnum from the following (in order of priority):
>  *   serial# env var
>  *   eeprom
>  */
> void get_board_serial(struct tag_serialnr *serialnr)

Right.

> serial# seems to be set generally in misc_init_r().
> But doing this on a per board level seems to be an inadequate design for
> i.mx6. The best place for i.mx6 seems to be arch_misc_init().

Yes, there's a number of reasonable examples of where to populate
serial# from, and a few examples from when we had to support the kernel
with it.

> @Tom:
> Linux Kconfig has:
> 
> CONFIG_ATAGS:
>  This is the traditional way of passing data to the kernel at boot time.
>  If you are solely relying on the flattened device tree (or
>  the ARM_ATAG_DTB_COMPAT option) then you may unselect this option
>  to remove ATAGS support from your kernel binary.  If unsure, leave this
>  to y.
> 
> CONFIG_DEPRECATED_PARAM_STRUCT
>  depends on ATAGS
>  This was deprecated in 2001 and announced to live on for 5 years.
>  Some old boot loaders still use this way.
> 
> As this has been deprecated 20 years ago, why don't we remove it from
> U-Boot?

The history is a lot more complex than that.  The earliest starting date
for "ATAGs is dead, use DT" would be 2010 or so when Linaro started real
work on migrating ARM to DT.  I also _think_ that deprecated param
struct note is about what predated ATAGs actually.

But, we can't universally drop ATAGs support from U-Boot as we support
hardware that runs on pre-device tree kernels only (Nokia N900) or older
VxWorks that also used ATAGs I _think__.  But we certainly have some
cases that should be cleaned up and disabled, hence my series yesterday.

-- 
Tom
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