Re: [RFC] spi-nor: fix cross die reads on Micron multi-die devices
From: Boris Brezillon
Date: Wed Jan 20 2016 - 07:25:00 EST
On Wed, 20 Jan 2016 12:01:06 +0000
Adam Somerville <adamsomerville@xxxxxxxxx> wrote:
> Thanks for looking at the this.
> I can rewrite so it only affects N25Q devices, I hoped a simpler
> implementation would outweigh the small overhead incurred on non
> affected devices.
I tend to think the same way: not sure the performance penalty is worth
> Do you know if there are any plans for MT25* based multi-die devices
> and if they would have the same issue?
> On Wed, Jan 20, 2016 at 2:45 AM, Bean Huo éææ (beanhuo)
> <beanhuo@xxxxxxxxxx> wrote:
> > Hi, Adam
> > This is true, but this only exist in Micron 65nm spi nor N25Q.
> > For our 45nm spi nor MT25Q , MT25TL and MT25Q, does exist this question.
> > So I think, can you differentiate between these in your patch?
> >> From: Adam Somerville <adamsomerville@xxxxxxxxx>
> >> So as far as I can see there is a bug in the spi-nor driver when issuing die
> >> boundary crossing reads on Micron multi-die devices.
> >> Micron N25Q512A, N25Q00AA and probably any other Micron multi-die
> >> devices do not support a single read request that crosses a die boundary.
> >> The current behaviour is that the address on the device wraps back to the
> >> start of the first die, with any data returned beyond the boundary being from
> >> the start of the first die.
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering