Re: [PATCH v1 00/12] Microchip OTPC driver on SAM9X60 exposing UIDxR as additional nvmem device

claudiu beznea
2024-08-24T16:17:47Z

Hi, Alexander,

On 21.08.2024 13:59, Alexander Dahl wrote:
> Hei hei,
>
> on a custom sam9x60 based board we want to access a unique ID of the
> SoC. Microchip sam-ba has a command 'readuniqueid' which returns the
> content of the OTPC Product UID x Register in that case.
>
> (On different boards with a SAMA5D2 we use the Serial Number x Register
> exposed through the atmel soc driver. Those registers are not present
> in the SAM9X60 series, but only for SAMA5D2/SAMA5D4 AFAIK.)

Not sure if you are talking about Chip ID, Chip ID extension registers.
These are available also on SAM9X60.

>
> There is a driver for the OTPC of the SAMA7G5 and after comparing
> register layouts it seems that one is almost identical to the one used
> by SAM9X60. Currently that driver has no support for the UIDx
> registers, but I suppose it would be the right place to implement it,
> because the registers are within the OTPC register address offsets.
>
> The patch series starts with fixups for the current driver. It then
> adds the necessary pieces to DT and driver to work on SAM9X60 in
> general. Later support for enabling the main RC oscillator is added,
> which is required on SAM9X60 for the OTPC to work. The last patch adds
> an additional nvmem device for the UIDx registers.
>
> This v1 of the series was _not_ tested on SAMA7G5, because I don't have
> such a board for testing. Actually I don't know if the main_rc_osc
> clock is required on SAMA7G5 too, and if yes how to handle that with
> regard to the different clock ids. If someone could test on SAMA7G5
> and/or help me sorting out the core clock id things, that would be
> highly appreciated.

Please add Nicolas in the loop on the next revisions of this series as this
should also be tested on SAMA7G5. I don't have a SAMA7G5 with OTP memory
populated.

>
> Also I assume some more devicetree and/or sysfs documentation is
> necessary. If someone could point me what's exactly required, this
> would be very helpful for me. You see I expect at least another version
> v2 of the series. ;-)
>
> Maybe some files having that "sama7g5" should be renamed, because that
> DT binding is used for more SoCs now and deserves a more generic name?

Not needed, adding your compatible there is enough.

> Thinking of these for example:
>
> - Documentation/devicetree/bindings/nvmem/microchip,sama7g5-otpc.yaml
> - include/dt-bindings/nvmem/microchip,sama7g5-otpc.h
>
> Are there other SoCs than SAMA7G5 and SAM9X60 using the same OTPC?
>
> Last question: Should the UID be added to the device entropy pool with
> add_device_randomness() as done in the SAMA5D2 sfr driver?
>
> I sent an RFC patch on this topic earlier this year, you'll find the
> link below as a reference to the discussion. The patch itself was
> trivial and not meant for applying as is anyways, so I decided to not
> write a full changelog from RFC to v1.
>
> Last not least, special thanks to Christian Melki on IRC, who wrote and
> tested parts of this, and was very kind and helpful in discussing the
> topic several times in the past months.
>
> Christian, if you feel there's credit missing, just point me where to
> add Co-developed-by and I'll happily do that for v2.
>
> Greets
> Alex
>
> (series based on v6.11-rc4)
>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: devicetree@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-clk@vger.kernel.org
> Link: https://lore.kernel.org/all/20240412140802.1571935-2-ada@thorsis.com/
>
> Alexander Dahl (12):
> nvmem: microchip-otpc: Avoid writing a write-only register
> nvmem: microchip-otpc: Fix swapped 'sleep' and 'timeout' parameters
> dt-bindings: nvmem: microchip-otpc: Add compatible for SAM9X60
> nvmem: microchip-otpc: Add SAM9X60 support
> ARM: dts: microchip: sam9x60: Add OTPC node
> ARM: dts: microchip: sam9x60_curiosity: Enable OTP Controller
> nvmem: microchip-otpc: Add missing register definitions
> nvmem: microchip-otpc: Add warnings for bad OTPC conditions on probe
> clk: at91: sam9x60: Allow enabling main_rc_osc through DT
> ARM: dts: microchip: sam9x60: Add clock properties to OTPC
> nvmem: microchip-otpc: Enable main RC oscillator clock
> nvmem: microchip-otpc: Expose UID registers as 2nd nvmem device
>
> .../nvmem/microchip,sama7g5-otpc.yaml | 1 +
> .../dts/microchip/at91-sam9x60_curiosity.dts | 4 +
> arch/arm/boot/dts/microchip/sam9x60.dtsi | 10 +++
> drivers/clk/at91/sam9x60.c | 3 +-
> drivers/nvmem/microchip-otpc.c | 86 ++++++++++++++++++-
> include/dt-bindings/clock/at91.h | 1 +
> 6 files changed, 100 insertions(+), 5 deletions(-)
>
>
> base-commit: 47ac09b91befbb6a235ab620c32af719f8208399