linux-kernel - [RFC PATCH 0/1] Timeout error with Microchip OTPC driver on SAM9X60

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Message-Id: <20240412140802.1571935-1-ada@thorsis.com>
Date: Fri, 12 Apr 2024 16:08:01 +0200
From: Alexander Dahl <ada@...rsis.com>
To: Claudiu Beznea <claudiu.beznea@...on.dev>
Cc: linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH 0/1] Timeout error with Microchip OTPC driver on SAM9X60

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 a different board with a SAMA5D2 we use the Serial Number x Register
exposed through the atmel soc driver, which is not present in the
SAM9X60 series.)

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.  So I thought just adapting the driver for SAM9X60 should be
easy.  (At least as a start, the driver has no support for that UID
register, but I suppose it would be the right place to implement it.)

However it does not work.  I used the patch attached with
additional debug messages on a SAM9X60-Curiosity board.  (That patch is
not meant for inclusion, just for showing what I've tried.)

On probe the function mchp_otpc_init_packets_list() returns with
ETIMEDOUT, which it can only do if mchp_otpc_prepare_read() returns with
timeout and that can only happen if read_poll_timeout() times out on
reading the Status Register.  Poking that register with `devmem
0xeff0000c 32` gives 0x00000040 which means "A packet read is on-going".

Kinda stuck here.  Any ideas?

Greets and have a nice weekend everyone
Alex

Alexander Dahl (1):
  nvmem: microchip-otpc: Add support for SAM9X60

 .../dts/microchip/at91-sam9x60_curiosity.dts     |  4 ++++
 arch/arm/boot/dts/microchip/sam9x60.dtsi         |  7 +++++++
 drivers/nvmem/microchip-otpc.c                   | 16 +++++++++++++---
 3 files changed, 24 insertions(+), 3 deletions(-)

base-commit: fec50db7033ea478773b159e0e2efb135270e3b7
-- 
2.39.2