linux-kernel - RE: [PATCH 1/1] mtd: spi-nor: everspin: add em004lxb entry

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Date: Thu, 1 Feb 2024 14:07:01 +0000
From: Flavio Suligoi <f.suligoi@...m.it>
To: Michael Walle <mwalle@...nel.org>
CC: Tudor Ambarus <tudor.ambarus@...aro.org>, Pratyush Yadav
	<pratyush@...nel.org>, Miquel Raynal <miquel.raynal@...tlin.com>, Richard
 Weinberger <richard@....at>, Vignesh Raghavendra <vigneshr@...com>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/1] mtd: spi-nor: everspin: add em004lxb entry

Hi Michael,

..

> Subject: Re: [PATCH 1/1] mtd: spi-nor: everspin: add em004lxb entry
> 
> Hi,
> 
> > Add the Everspin EM0004LXB 4Mb (512KB) Industrial STT-MRAM Persistent
> > Memory.
> 
> Out of curiosity, what is your use case here? Usually, I push back on this small
> MRAM devices in SPI-NOR in favor of the at25 driver. But this datasheet lists
> octal dtr with 200mhz, which seems a bit ridiculous for 512kB. The at25 driver
> only supports single bit SPI of course.
> 
> I'm not sure in which mode you are using this device, though. The DS shows a
> non-volatile configuration register (Table 10, offset 0) and it's default value is
> single bit SPI.
..

We adopted the MRAM to save some important application data in case of
power loss (there are some super-capacitors to maintain the power for a few
seconds).
We use this MRAM in single SPI mode (MISO, MOSI, clock and CS).
About the SPI frequency,  we use only 30MHz, because it is a hw limit of the
MX8MP CPU.

I used the SPI-NOR driver, instead of at25, because in everspin.c there are other
Everspin MRAMs devices (already used in other our boards).

Best regards,
Flavio