linux-kernel - Re: [PATCH v13 06/15] mtd: spi-nor: sfdp: parse xSPI Profile 1.0 table

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Message-ID: <20200930065325.umw6kf3m3vzq4r5z@ti.com>
Date:   Wed, 30 Sep 2020 12:23:27 +0530
From:   Pratyush Yadav <p.yadav@...com>
To:     <Tudor.Ambarus@...rochip.com>
CC:     <miquel.raynal@...tlin.com>, <richard@....at>, <vigneshr@...com>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <nsekhar@...com>, <boris.brezillon@...labora.com>
Subject: Re: [PATCH v13 06/15] mtd: spi-nor: sfdp: parse xSPI Profile 1.0
 table

On 30/09/20 06:44AM, Tudor.Ambarus@...rochip.com wrote:
> On 9/16/20 3:44 PM, Pratyush Yadav wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > This table is indication that the flash is xSPI compliant and hence
> > supports octal DTR mode. Extract information like the fast read opcode,
> > dummy cycles, the number of dummy cycles needed for a Read Status
> > Register command, and the number of address bytes needed for a Read
> > Status Register command.
> > 
> > We don't know what speed the controller is running at. Find the fast
> > read dummy cycles for the fastest frequency the flash can run at to be
> > sure we are never short of dummy cycles. If nothing is available,
> > default to 20. Flashes that use a different value should update it in
> > their fixup hooks.
> > 
> > Since we want to set read settings, expose spi_nor_set_read_settings()
> > in core.h.
> > 
> > Signed-off-by: Pratyush Yadav <p.yadav@...com>
> > ---
> >  drivers/mtd/spi-nor/core.c |  2 +-
> >  drivers/mtd/spi-nor/core.h | 10 +++++
> >  drivers/mtd/spi-nor/sfdp.c | 91 ++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 102 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> > index 7445d7122304..cbb1aab27d03 100644
> > --- a/drivers/mtd/spi-nor/core.c
> > +++ b/drivers/mtd/spi-nor/core.c
...
> > @@ -1108,6 +1110,91 @@ static int spi_nor_parse_4bait(struct spi_nor 
> > *nor,
> >         return ret;
> >  }
> > 
> > +#define PROFILE1_DWORD1_RDSR_ADDR_BYTES                BIT(29)
> > +#define PROFILE1_DWORD1_RDSR_DUMMY             BIT(28)
> > +#define PROFILE1_DWORD1_RD_FAST_CMD            GENMASK(15, 8)
> > +#define PROFILE1_DWORD4_DUMMY_200MHZ           GENMASK(11, 7)
> > +#define PROFILE1_DWORD5_DUMMY_166MHZ           GENMASK(31, 27)
> > +#define PROFILE1_DWORD5_DUMMY_133MHZ           GENMASK(21, 17)
> > +#define PROFILE1_DWORD5_DUMMY_100MHZ           GENMASK(11, 7)
> > +#define PROFILE1_DUMMY_DEFAULT                 20
> > +
> > +/**
> > + * spi_nor_parse_profile1() - parse the xSPI Profile 1.0 table
> > + * @nor:               pointer to a 'struct spi_nor'
> > + * @profile1_header:   pointer to the 'struct sfdp_parameter_header' describing
> > + *                     the 4-Byte Address Instruction Table length and version.
> 
> Profile 1.0 Table

Oops! Will fix.
 
> > + * @params:            pointer to the 'struct spi_nor_flash_parameter' to be.
> > + *
> > + * Return: 0 on success, -errno otherwise.
> > + */
...
> > +       /*
> > +        * We don't know what speed the controller is running at. Find the
> > +        * dummy cycles for the fastest frequency the flash can run at to be
> > +        * sure we are never short of dummy cycles. A value of 0 means the
> > +        * frequency is not supported.
> > +        *
> > +        * Default to PROFILE1_DUMMY_DEFAULT if we don't find anything, and let
> > +        * flashes set the correct value if needed in their fixup hooks.
> > +        */
> > +       dummy = FIELD_GET(PROFILE1_DWORD4_DUMMY_200MHZ, dwords[3]);
> > +       if (!dummy)
> > +               dummy = FIELD_GET(PROFILE1_DWORD5_DUMMY_166MHZ, dwords[4]);
> > +       if (!dummy)
> > +               dummy = FIELD_GET(PROFILE1_DWORD5_DUMMY_133MHZ, dwords[4]);
> > +       if (!dummy)
> > +               dummy = FIELD_GET(PROFILE1_DWORD5_DUMMY_100MHZ, dwords[4]);
> > +       if (!dummy)
> > +               dummy = PROFILE1_DUMMY_DEFAULT;
> 
> just a dev_dbg here, without assuming what default value means

And we leave dummy to 0, correct?

-- 
Regards,
Pratyush Yadav
Texas Instruments India