[U-Boot] [PATCH] sf: ensure flash device is in 3-byte address mode

[Goldschmidt Simon]

On 2017-10-07 09:23 AM, Prabhakar Kushwaha wrote:
> Dear Jagan, Simon,
> 
> > -----Original Message-----
> > From: U-Boot [mailto:u-boot-bounces at lists.denx.de] On Behalf Of Jagan
> > Teki
> > Sent: Thursday, December 07, 2017 11:19 AM
> > To: Goldschmidt Simon <sgoldschmidt at de.pepperl-fuchs.com>
> > Cc: u-boot at lists.denx.de
> > Subject: Re: [U-Boot] [PATCH] sf: ensure flash device is in 3-byte
> > address mode
> >
> > On Tue, Dec 5, 2017 at 11:50 AM, Goldschmidt Simon
> > <sgoldschmidt at de.pepperl-fuchs.com> wrote:
> > > + Lukasz (as a reviewer of my patch[1])
> > >
> > > On Mon, Dec 4, 2017 at 8:20, Jagan Teki wrote:
> > >> This is the patch[1] for 4-byte addressing, but I would wonder how
> > >> can
> > proceed
> > >> operations with 4-byte if we disable during probe.
> > >>
> > >> [1]
> > https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fgit.
> > denx
> > .de%2F%3Fp%3Du-boot-
> > &data=02%7C01%7Cprabhakar.kushwaha%40nxp.com%7Ca37e67c0f5fd431396
> > 5f08d53d3649b8%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6364
> >
> 82225771650679&sdata=CBQkKDXTE1g1mvEbYuyiBApW2NTxQFCirGeJV9uzX8E
> > %3D&reserved=0
> > >> spi.git;a=commitdiff;h=fd0c22a90772379c4c11ba09347d36cc8ee17dca
> > >
> > > OK, so your patch does something different than what I did.
> > >
> > > I was trying to keep the change to U-Boot as small as possible, only
> > > fixing this issue I was seeing:
> > >
> > > After a soft-reboot where the SPI chip was not reset, it is left in
> > > 4-byte addressing mode (linux uses this mode, obviously). Remember
> > > that 4-byte mode is not a permanent setting, so we can enter and
> > > leave it any time we like by issuing a command.
> > >
> > > U-Boot uses the Bank Address Register (BAR) for spi flash chips with
> > > more than 16 MByte, so it impclitly assumes that the chip is in
> > > 3-byte address mode. As I see it, your patch is worth a discussion
> > > named "should we use 4-byte addressing mode on spi flash chips?".
> > > I do think this is a better alternative than writing BAR! But this
> > > change probably needs discussion and testing.
> >
> > OK, will review your patch.
> >
> 
> Other solution to this problem could have been "adding support of 4byte
> addressing".
> 
> There will always be a requirement of supporting >16MB flash.

I would be very happy to have 4-byte addressing support. I just
thought it would be better to first fix the soft-reboot issue I am
having (and at least one other person on this list also had).

Plus, I haven't seen a workign patch for 4-byte addressing on this
list, yet. My patch has no side effects, works and could be merged
for 2018.01.

Thanks,
Simon