[PATCH v7 2/2] mtd: fsl-quadspi: fix init AHB read in fsl_qspi_nor_setup()

[Yogesh Narayan Gaur]

Hi Frieder,

> -----Original Message-----
> From: linux-mtd [mailto:linux-mtd-bounces at lists.infradead.org] On Behalf Of
> Frieder Schrempf
> Sent: Thursday, March 22, 2018 2:49 PM
> To: Yogesh Narayan Gaur <yogeshnarayan.gaur at nxp.com>; linux-
> mtd at lists.infradead.org
> Cc: boris.brezillon at free-electrons.com; marek.vasut at gmail.com; Prabhakar
> Kushwaha <prabhakar.kushwaha at nxp.com>; Suresh Gupta
> <suresh.gupta at nxp.com>; cyrille.pitchen at wedev4u.fr; Han Xu
> <han.xu at nxp.com>; computersforpeace at gmail.com; festevam at gmail.com
> Subject: Re: [PATCH v7 2/2] mtd: fsl-quadspi: fix init AHB read in
> fsl_qspi_nor_setup()
> 
> Hi Yogesh,
> 
> On 21.03.2018 12:26, Yogesh Gaur wrote:
> > Move AHB read initialize in fsl_qspi_nor_setup().
> >
> > In file spi-nor.c, func spi_nor_scan() calls nor->read() thru
> > spi_nor_read_sfdp() API.
> >
> > Presently, fsl_qspi_init_ahb_read() called from fsl_qspi_nor_setup_last().
> > Func fsl_qspi_probe() calls spi_nor_scan() first and then calls
> > fsl_qspi_nor_setup_last().
> >
> > When nor->read() being called from inside spi_nor_read_sfdp(), QSPI
> > cntlr AHB mode initialization is not yet done results in data read error.
> >
> > Initialize AHB read inside fsl_qspi_nor_setup().
> >
> > Signed-off-by: Yogesh Gaur <yogeshnarayan.gaur at nxp.com>
> > ---
> > Changes for v7:
> > - None
> > Changes for v6:
> > - None
> > Changes for v5:
> > - None
> > Changes for v4:
> > - None
> > Changes for v3:
> > - None
> > Changes for v2:
> > - None
> >
> >   drivers/mtd/spi-nor/fsl-quadspi.c | 6 +++---
> >   1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/mtd/spi-nor/fsl-quadspi.c
> > b/drivers/mtd/spi-nor/fsl-quadspi.c
> > index 64b8bb3..424094a 100644
> > --- a/drivers/mtd/spi-nor/fsl-quadspi.c
> > +++ b/drivers/mtd/spi-nor/fsl-quadspi.c
> > @@ -820,6 +820,9 @@ static int fsl_qspi_nor_setup(struct fsl_qspi *q)
> >   	/* enable the interrupt */
> >   	qspi_writel(q, QUADSPI_RSER_TFIE, q->iobase + QUADSPI_RSER);
> >
> > +	/* Init for AHB read */
> > +	fsl_qspi_init_ahb_read(q);
> 
> Maybe I missed something, but it seems if you move
> fsl_qspi_init_ahb_read() here and fsl_qspi_read() is used before
> fsl_qspi_nor_setup_last() is called, then the read command is triggered with an
> uninitialized LUT entry (SEQID_LUT2_AHBREAD).
> 
For every call to fsl_qspi_read(), I am preparing the LUT before doing actual read so LUT entry for SEQID_LUT2_AHBREAD is never be uninitialized.

Rationale behind moving fsl_qspi_init_ahb_read() from fsl_qspi_nor_setup_last() to fsl_qspi_nor_setup() is to initialize registers which are required for AHB read operation like setting of values in QUADSPI_BUF3CR, QUADSPI_BFGENCR etc registers as fsl_qspi_read() is called, before call to fsl_qspi_nor_setup_last(), through spi_nor_read_sfdp().

--
Thanks
Yogesh Gaur

> So shouldn't the LUT entry for AHB read be initialized with some default values
> here, before spi_nor_scan() is called?
> 
> Thanks,
> 
> Frieder
> 
> > +
> >   	return 0;
> >   }
> >
> > @@ -842,9 +845,6 @@ static int fsl_qspi_nor_setup_last(struct fsl_qspi *q)
> >   	if (ret)
> >   		return ret;
> >
> > -	/* Init for AHB read */
> > -	fsl_qspi_init_ahb_read(q);
> > -
> >   	/* Prepare LUT for AHB read - required for read from devmem interface
> */
> >   	fsl_qspi_prep_ahb_read(q);
> >
> >
> 
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