lkml.org 
[lkml]   [2021]   [Nov]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/4] mtd: rawnand: fsmc: Force to use 8 bits access when expected
Hi,

On Fri, 12 Nov 2021 16:38:59 +0100
Miquel Raynal <miquel.raynal@bootlin.com> wrote:

> Hi Hervé,
>
> herve.codina@bootlin.com wrote on Fri, 12 Nov 2021 15:38:53 +0100:
>
> > Some data transfers are expected on 8 bits by the nand core.
> > The fsmc driver did not check this constraint and these transfers
> > can be done on 32 bits depending on buffer alignment and transfers
> > data size.
> >
> > This patch ensures that these transfers will be 8bits transfers in
> > all cases.
>
> I believe there is a misunderstanding here: NAND buses -between the
> NAND controller and the NAND chip- are either 8-bit or 16-bit wide and
> the amount of bytes that you will retrieve per register read is not
> related to it.
>
> When the controller supports 16-bit accesses, there are certain
> operations that must be performed using only the lowest 8 bits of the
> NAND bus, such as reading a status [1]. In this case, the controller
> must have a way to disable the 16-bit mode temporarily. See [2] and [3]
> for an example. Reading with readb() or readl() will IMHO not impact the
> amount of data lines used for the operation.
>

Indeed, I misunderstood the force_8bit usage.
This patch is not needed and will be simply removed in v2 series.

Thanks,
Hervé

\
 
 \ /
  Last update: 2021-11-17 14:48    [W:0.063 / U:0.108 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site