Re: [PATCH] spi-nor: intel-spi: Whitelist 4B read commands

From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: Tudor.Ambarus@microchip.com
Cc: vigneshr@ti.com, richard@nod.at, marek.vasut@gmail.com,
	linux-mtd@lists.infradead.org, miquel.raynal@bootlin.com,
	alexander.sverdlin@nokia.com, computersforpeace@gmail.com,
	dwmw2@infradead.org
Subject: Re: [PATCH] spi-nor: intel-spi: Whitelist 4B read commands
Date: Wed, 21 Aug 2019 10:34:25 +0300	[thread overview]
Message-ID: <20190821073425.GN19908@lahna.fi.intel.com> (raw)
In-Reply-To: <409a9e10-e391-2403-5aff-c2e5a361fdef@microchip.com>

On Tue, Aug 20, 2019 at 03:24:37PM +0000, Tudor.Ambarus@microchip.com wrote:
> Mika,
> 
> Would you please review the patch from below?

Sure.

> 
> Thanks,
> ta
> 
> On 07/12/2019 03:14 PM, Sverdlin, Alexander (Nokia - DE/Ulm) wrote:
> > External E-Mail
> > 
> > 
> > From: Alexander Sverdlin <alexander.sverdlin@nokia.com>
> > 
> > spi-nor.c issues 4B commands for some Flash chips bigger than 16Mbytes.
> > Xeon(R) D-1500 documentation mentions its Integrated PCH Logic supports
> > Flash chips up to 64Mbytes.
> > D-1500 Integrated PCH documenation however has inconsistencies regarding
> > FADDR register width and says nothing about particular commands issued
> > to support 64Mbytes of Flash.

Unfortunately I don't have any additional documentation that could help.

> > Nevetheless the tests on Xeon(R) CPU D-1548 with 512Mbit Flash chips
> > Macronix MX25L51245G and Micron MT25QL512A showed that erase, write and
> > read operations work just fine after SPINOR_OP_READ_4B and
> > SPINOR_OP_READ_FAST_4B are white-listed (currently only
> > SPINOR_OP_READ_FAST_4B is used and only for Macronix).

If it works in your testing I don't see why we would not support them
especially since these are just reads.

> > Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>

The patch itself is trivial enough and looks fine to me.

Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

> > ---
> >  drivers/mtd/spi-nor/intel-spi.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/mtd/spi-nor/intel-spi.c b/drivers/mtd/spi-nor/intel-spi.c
> > index 1ccf23f..43e55a2e 100644
> > --- a/drivers/mtd/spi-nor/intel-spi.c
> > +++ b/drivers/mtd/spi-nor/intel-spi.c
> > @@ -621,6 +621,8 @@ static ssize_t intel_spi_read(struct spi_nor *nor, loff_t from, size_t len,
> >  	switch (nor->read_opcode) {
> >  	case SPINOR_OP_READ:
> >  	case SPINOR_OP_READ_FAST:
> > +	case SPINOR_OP_READ_4B:
> > +	case SPINOR_OP_READ_FAST_4B:
> >  		break;
> >  	default:
> >  		return -EINVAL;
> > 

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