linux-kernel - Re: [PATCH] eeprom: at25: convert to spi-mem API

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Message-ID: <e0037dc532f3aecb101c78e7d91b66430b15d541.camel@siemens.com>
Date: Fri, 7 Nov 2025 11:49:51 +0000
From: "Sverdlin, Alexander" <alexander.sverdlin@...mens.com>
To: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"christophe.leroy@...roup.eu" <christophe.leroy@...roup.eu>
CC: "hui.wang@...onical.com" <hui.wang@...onical.com>, "mwalle@...nel.org"
	<mwalle@...nel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "florent.trinh-thai@...soprasteria.com"
	<florent.trinh-thai@...soprasteria.com>, "arnd@...db.de" <arnd@...db.de>
Subject: Re: [PATCH] eeprom: at25: convert to spi-mem API

Hi Greg, Christophe,

On Wed, 2025-11-05 at 08:20 +0100, Alexander Sverdlin wrote:
> > > > Replace the RAW SPI accesses with spi-mem API. The latter will fall back to
> > > > RAW SPI accesses if spi-mem callbacks are not implemented by a controller
> > > > driver.
> > > 
> > > With this patch (kernel v6.17.1) our powerpc boards are totally unstable, we
> > > get multiple random Oops due to bad memory accesses.
> > > 
> > > With this commit reverted the board is stable again.
> > > 
> > > The SPI driver is:
> > > 
> > > CONFIG_SPI=y
> > > CONFIG_SPI_MASTER=y
> > > CONFIG_SPI_MEM=y
> > > CONFIG_SPI_FSL_LIB=y
> > > CONFIG_SPI_FSL_CPM=y
> > > CONFIG_SPI_FSL_SPI=y
> > > 
> > > How can we further investigate the issue ?
> > 
> > We can revert it until it comes back working properly.  Can you send a
> > revert so that I can apply it?
> 
> what is known for sure is that it triggers a bug in SPI_FSL_CPM [1],
> which probably justifies a revert in -stable. But there are no indications the
> patch in question misbehaves itself as of now. I'm going to KASAN it on all the
> HW I can get my hands on this week.
> 
> [1] https://lore.kernel.org/all/764858d5-5633-4aeb-aabe-52f9eb1eb530@csgroup.eu/

just letting you know that I stress-tested the at25 driver with KASAN on two ARM64
platforms, TI AM62 and i.MX8QXP, in the latter case it's even spi-nxp-fspi driver
only providing spi-mem API, while the TI SoC goes over normal SPI. Up to now it
went smoothly.

Christophe, while I'm trying to get my hands on a PPC32 HW similar to yours, would
you be able to test with CONFIG_DMA_API_DEBUG=y? The fact the KASAN doesn't detect
anything after the fix to spi-fsl-cpm you've mentioned makes me think the corruption
is external to CPU core? Will you post you fix to fsl-cpm code?

-- 
Alexander Sverdlin
Siemens AG
www.siemens.com