[PATCH 1/2] arm: layerscape: Add sfp driver

[Sean Anderson]

On 4/19/22 4:58 PM, Sean Anderson wrote:
> This adds a driver for the Security Fuse Processor (SFP) present on
> LS1012A, LS1021A, LS1043A, and LS1046A processors. It holds the
> Super-Root Key (SRK), One-Time-Programmable Master Key (OTPMK), and
> other "security" related fuses. Similar devices (sharing the same name)
> are present on other processors, but for the moment this just supports
> the LS2 variants.
> 
> The mirror registers are loaded during power-on reset. All mirror
> registers must be programmed or read at once. Because of this, `fuse
> prog` will program all fuses, even though only one might be specified.
> To prevent accidentally burning through all your fuse programming cycles
> with something like `fuse prog 0 0 A B C D`, we limit ourselves to one
> programming cycle per reset. Fuses are numbered based on their address.
> The fuse at 0x1e80200 is 0, the fuse at 0x1e80204 is 1, etc.
> 
> The TA_PROG_SFP supply must be enabled when programming fuses, but must
> be disabled when reading them. Typically this supply is enabled by
> inserting a jumper or by setting a register in the board's FPGA. I've
> also added support for using a regulator. This could be helpful for
> automatically issuing the FPGA write, or for toggling a GPIO controlling
> the supply.
> 
> I suggest using the following procedure for programming:
> 
> 1. Override the fuses you wish to program
>    => fuse override 0 2 A B C D
> 2. Inspect the values and ensure that they are what you expect
>    => fuse sense 0 2 4
> 3. Enable TA_PROG_SFP
> 4. Issue a program command using OSPR0 as a dummy. Since it contains the
>    write-protect bit you will usually want to write it last anyway.
>    => fuse prog 0 0 0
> 5. Disable TA_PROG_SFP
> 6. Read back the fuses and ensure they are correct
>    => fuse read 0 2 4
> 
> Signed-off-by: Sean Anderson <sean.anderson at seco.com>
> ---

I forgot to mention this, but this patch depends on

https://lore.kernel.org/u-boot/20220419191245.3749739-1-sean.anderson@seco.com/T/#u