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

[Bin Meng]

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?

Regards,
Bin