linux-kernel - Re: [RFC PATCH 0/2] eeprom: at25: support Cypress FRAMs without device ID

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Message-ID: <Z-zr2oj-hD28ccy3@KAN23-025>
Date: Wed, 2 Apr 2025 07:48:52 +0000
From: Markus Heidelberg <M.Heidelberg@....de>
To: Christian Eggers <ceggers@...i.de>
CC: Arnd Bergmann <arnd@...db.de>, Greg Kroah-Hartman
	<gregkh@...uxfoundation.org>, Rob Herring <robh@...nel.org>, "Krzysztof
 Kozlowski" <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, "Jiri
 Prchal" <jiri.prchal@...ignal.cz>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>
Subject: Re: [RFC PATCH 0/2] eeprom: at25: support Cypress FRAMs without
 device ID

Hi Christian,

On Tue, Apr 01, 2025 at 03:45:14PM +0200, Christian Eggers wrote:
> 
> I use the following FRAM device: Fujitsu mb85rs1mt. 
> 
> This FRAM is also not able to report its size (at least I didn't
> try).

According to the datasheet there is a device ID, but with a different
response compared to Cypress FRAMs. It wouldn't work without modifying
the current implementation.

> I can use this FRAM with the following (Eeeprom) settings:
> 
> 		compatible = "fujitsu,mb85rs1mt", "atmel,at25";
> 		reg = <0>;
> 		spi-max-frequency = <30000000>;
> 		/* mode0, uncomment for mode3 */
> 		/*spi-cpha;
> 		spi-cpol;*/
> 
> 		/* from the datasheet it seems that there is no page size for FRAM */
> 		pagesize = <131072>;
> 		size = <131072>;
> 		address-width = <24>;
> 
> Is this what you are looking for? Of course, the "type" attribute 
> reports "EEPROM" with this configuration, but my application don't care
> about this.

This is what I started with, but I thought there has to be a reason that
EEPROM and FRAM are distinguished in the driver (at25 and nvmem core)
and I wanted to do it right. If not relevant now, maybe in the future.

Markus