[U-Boot Patch v2 3/4] dts: u-boot.dtsi: override flash tx-rx width

[Sagar Kadam]

Hello Jagan,

> -----Original Message-----
> From: Bin Meng <bmeng.cn at gmail.com>
> Sent: Wednesday, February 19, 2020 9:59 PM
> To: Sagar Kadam <sagar.kadam at sifive.com>
> Cc: U-Boot Mailing List <u-boot at lists.denx.de>; Rick Chen
> <rick at andestech.com>; Paul Walmsley ( Sifive) <paul.walmsley at sifive.com>;
> Jagan Teki <jagan at amarulasolutions.com>; Anup Patel
> <anup.patel at wdc.com>
> Subject: Re: [U-Boot Patch v2 3/4] dts: u-boot.dtsi: override flash tx-rx width
> 
> Hi Sagar,
> 
> On Fri, Feb 7, 2020 at 2:43 AM Sagar Kadam <sagar.kadam at sifive.com>
> wrote:
> >
> > Hello Bin,
> >
> > > -----Original Message-----
> > > From: Bin Meng <bmeng.cn at gmail.com>
> > > Sent: Tuesday, February 4, 2020 5:43 PM
> > > To: Sagar Kadam <sagar.kadam at sifive.com>
> > > Cc: U-Boot Mailing List <u-boot at lists.denx.de>; Rick Chen
> > > <rick at andestech.com>; Paul Walmsley ( Sifive)
> > > <paul.walmsley at sifive.com>; Jagan Teki
> <jagan at amarulasolutions.com>;
> > > Anup Patel <anup.patel at wdc.com>
> > > Subject: Re: [U-Boot Patch v2 3/4] dts: u-boot.dtsi: override flash
> > > tx-rx width
> > >
> > > Hi Sagar,
> > >
> > > On Wed, Jan 29, 2020 at 2:02 AM Sagar Shrikant Kadam
> > > <sagar.kadam at sifive.com> wrote:
> > > >
> > > > The hifive-unleashed-a00.dts has flash spi-tx/rx width set to
> > > > 4-bit mode. During sf probe, spi_nor_scan fails to read the JEDEC
> > > > ID with reg_proto set to SNOR_PROTO_1_1_1. Setting it to 1-bit
> > > > mode as of now will help read the JEDEC-ID and perform other flash
> operations.
> > >
> > > So previously with Jagan's series that did not have these changes in
> > > this commit, the flash driver worked well. I wonder what real issue
> > > was fixed in this commit?
> > >
> > Yes true, I had observed that flash device was working with Jagan's
> > series you are indicating here. The flash device was getting probed at cs
> 2/4/6/8 etc..
> > but it couldn't get detected on CS0 which is actually connected on the
> > board to the flash device.
> > With the check of spi->num_cs done in patch 2 of this series or the
> > one handled in commit 7bacce524d48 ("dm: spi: Check cs number before
> > accessing slaves") invalid chip select is taken care of and flash is
> > not detected on wrong chip selects, but spi transfer still fails as
> > the sifive-spi driver set's the SIFIVE_SPI_FMT_PROTO_QUAD mode based
> > on device tree information. While reading Device ID in spi_nor_scan
> > the reg proto is set to 1_1_1 bit mode and this contradicts here in the driver
> due to which spi_nor_scan fails, due to which one cannot use the flash.
> > So for now I have added this override here to 1 bit mode so that users can
> use it.
> > Maybe I will update the commit message to indicate that this is
> > workaround for a bug in SPI driver for FU540 which currently is not able to
> handle QUAD mode operation.
> > Please let me know your views here.
> >
> 
> Thanks for the details. Based on your description, I think there is something
> wrong with the SPI-NOR driver. Your change to 1 line only seems to be a
> workaround.
> 
> Jagan, would you please comment?
> 

It would be good if you could also share some input's here.

Thanks & BR,
Sagar Kadam

> Regards,
> Bin