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

["Sverdlin, Alexander" <alexander.sverdlin@siemens.com>]

Hi Greg,

On Wed, 2025-11-05 at 08:15 +0900, Greg Kroah-Hartman 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/

-- 
Alexander Sverdlin
Siemens AG
www.siemens.com