linux-kernel - Re: [PATCH v10 12/17] mtd: spi-nor: sfdp: detect Soft Reset sequence support from BFPT

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Message-ID: <20200720162130.hknyyclgndjokqly@yadavpratyush.com>
Date:   Mon, 20 Jul 2020 21:51:30 +0530
From:   Pratyush Yadav <me@...avpratyush.com>
To:     Tudor.Ambarus@...rochip.com
Cc:     p.yadav@...com, miquel.raynal@...tlin.com, richard@....at,
        vigneshr@...com, broonie@...nel.org, Nicolas.Ferre@...rochip.com,
        alexandre.belloni@...tlin.com, Ludovic.Desroches@...rochip.com,
        matthias.bgg@...il.com, michal.simek@...inx.com,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-spi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, boris.brezillon@...labora.com,
        nsekhar@...com
Subject: Re: [PATCH v10 12/17] mtd: spi-nor: sfdp: detect Soft Reset sequence
 support from BFPT

Hi Tudor,

On 08/07/20 04:08PM, Tudor.Ambarus@...rochip.com wrote:
> On 6/23/20 9:30 PM, Pratyush Yadav wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > A Soft Reset sequence will return the flash to Power-on-Reset (POR)
> > state. It consists of two commands: Soft Reset Enable and Soft Reset.
> > Find out if the sequence is supported from BFPT DWORD 16.
> > 
> > Signed-off-by: Pratyush Yadav <p.yadav@...com>
> > ---
> >  drivers/mtd/spi-nor/core.h | 1 +
> >  drivers/mtd/spi-nor/sfdp.c | 4 ++++
> >  drivers/mtd/spi-nor/sfdp.h | 2 ++
> >  3 files changed, 7 insertions(+)
> > 
> > diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
> > index 6338d32a0d77..79ce952c0539 100644
> > --- a/drivers/mtd/spi-nor/core.h
> > +++ b/drivers/mtd/spi-nor/core.h
> > @@ -26,6 +26,7 @@ enum spi_nor_option_flags {
> >         SNOR_F_HAS_SR_TB_BIT6   = BIT(11),
> >         SNOR_F_HAS_4BIT_BP      = BIT(12),
> >         SNOR_F_HAS_SR_BP3_BIT6  = BIT(13),
> > +       SNOR_F_SOFT_RESET       = BIT(14),
> >  };
> > 
> >  struct spi_nor_read_command {
> > diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
> > index 7983ff431346..8e0741d8bfd3 100644
> > --- a/drivers/mtd/spi-nor/sfdp.c
> > +++ b/drivers/mtd/spi-nor/sfdp.c
> > @@ -616,6 +616,10 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
> >                 break;
> >         }
> > 
> > +       /* Soft Reset support. */
> > +       if (bfpt.dwords[BFPT_DWORD(16)] & BFPT_DWORD16_SOFT_RST)
> 
> this can be improved. There are multiple reset methods described and you're
> addressing just one of them.

Yes, it can be. But xSPI only cares about the 0x66 and 0x99 reset 
sequence and that is what I implemented. Others can be added if they are 
needed in the future. In addition, I don't have hardware that supports 
these resets so I can't test them. IMO if someone needs other reset 
modes, they should send a separate patch for it.

If you are worried about future work needed to support multiple soft 
reset modes, I can introduce a nor->soft_reset() hook that can be 
populated when parsing BFPT. But I think that is a bit premature. The 
work needed to do that is not a lot so I think we should hold off until 
the need really comes up.
 
> > +               nor->flags |= SNOR_F_SOFT_RESET;
> > +
> >         /* Stop here if not JESD216 rev C or later. */
> >         if (bfpt_header->length == BFPT_DWORD_MAX_JESD216B)
> >                 return spi_nor_post_bfpt_fixups(nor, bfpt_header, &bfpt,
> > diff --git a/drivers/mtd/spi-nor/sfdp.h b/drivers/mtd/spi-nor/sfdp.h
> > index 6d7243067252..8ae55e98084e 100644
> > --- a/drivers/mtd/spi-nor/sfdp.h
> > +++ b/drivers/mtd/spi-nor/sfdp.h
> > @@ -90,6 +90,8 @@ struct sfdp_bfpt {
> >  #define BFPT_DWORD15_QER_SR2_BIT1_NO_RD                (0x4UL << 20)
> >  #define BFPT_DWORD15_QER_SR2_BIT1              (0x5UL << 20) /* Spansion */
> > 
> > +#define BFPT_DWORD16_SOFT_RST                  BIT(12)
> > +
> >  #define BFPT_DWORD18_CMD_EXT_MASK              GENMASK(30, 29)
> >  #define BFPT_DWORD18_CMD_EXT_REP               (0x0UL << 29) /* Repeat */
> >  #define BFPT_DWORD18_CMD_EXT_INV               (0x1UL << 29) /* Invert */

-- 
Regards,
Pratyush Yadav