Re: [PATCH v2 3/4] mtd:spi-nor:fsl-quadspi:Add fast-read mode support

[Han Xu <xhnjupt@gmail.com>]

On Thu, Feb 25, 2016 at 08:07:22AM +0000, Yunhui Cui wrote:
> Hi Han,
> 
> I have provided the options " m25p,fast-read ", because there are probable some flashes can't support quad mode.
> So we should support fast-read mode in our driver. Moreover,  There is a option to select fast-read mode in spi_nor.c :
>                /* If we were instantiated by DT, use it */
>                  if (of_property_read_bool(np, "m25p,fast-read"))
>                          nor->flash_read = SPI_NOR_FAST;

Did you have some REAL cases using SPI NOR that only supports upto fast-read
with Quad SPI driver? Neither fast-read or normal-read, which is actually more
general, supported in the driver, just because I didn't see any REAL cases till
now.

I didn't run against the patch, although IMO it's not that necessary. But I
don't think QuadSPI driver need to check the m25p,fast-read property again
since spi-nor layer has already done that. Adding the property in flash node
should work in the same way.
 
> 
> Thanks
> Yunhui
> 
> -----Original Message-----
> From: Han Xu [mailto:xhnjupt@gmail.com] 
> Sent: Thursday, February 18, 2016 2:08 AM
> To: Yunhui Cui
> Cc: dwmw2@infradead.org; computersforpeace@gmail.com; han.xu@freescale.com; linux-mtd@lists.infradead.org; linux-kernel@vger.kernel.org; linux-arm-kernel@lists.infradead.org; Yao Yuan
> Subject: Re: [PATCH v2 3/4] mtd:spi-nor:fsl-quadspi:Add fast-read mode support
> 
> On Mon, Feb 01, 2016 at 07:30:07PM +0800, Yunhui Cui wrote:
> > The qspi driver add generic fast-read mode for different flash 
> > venders. There are some different board flash work on different mode, 
> > such fast-read, quad-mode.
> > So we have to modify the third entrace parameter of spi_nor_scan().
> > 
> > Signed-off-by: Yunhui Cui <B56489@freescale.com>
> > ---
> >  drivers/mtd/spi-nor/fsl-quadspi.c | 27 +++++++++++++++++++++------
> >  1 file changed, 21 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/mtd/spi-nor/fsl-quadspi.c 
> > b/drivers/mtd/spi-nor/fsl-quadspi.c
> > index 9861290..0a31cb1 100644
> > --- a/drivers/mtd/spi-nor/fsl-quadspi.c
> > +++ b/drivers/mtd/spi-nor/fsl-quadspi.c
> > @@ -389,11 +389,21 @@ static void fsl_qspi_init_lut(struct fsl_qspi *q)
> >  	/* Read */
> >  	lut_base = SEQID_READ * 4;
> >  
> > -	qspi_writel(q, LUT0(CMD, PAD1, read_op) | LUT1(ADDR, PAD1, addrlen),
> > -			base + QUADSPI_LUT(lut_base));
> > -	qspi_writel(q, LUT0(DUMMY, PAD1, read_dm) |
> > -		    LUT1(FSL_READ, PAD4, rxfifo),
> > -			base + QUADSPI_LUT(lut_base + 1));
> > +	if (nor->flash_read == SPI_NOR_FAST) {
> > +		qspi_writel(q, LUT0(CMD, PAD1, read_op) |
> > +			    LUT1(ADDR, PAD1, addrlen),
> > +				base + QUADSPI_LUT(lut_base));
> > +		qspi_writel(q,  LUT0(DUMMY, PAD1, read_dm) |
> > +			    LUT1(FSL_READ, PAD1, rxfifo),
> > +				base + QUADSPI_LUT(lut_base + 1));
> > +	} else if (nor->flash_read == SPI_NOR_QUAD) {
> > +		qspi_writel(q, LUT0(CMD, PAD1, read_op) |
> > +			    LUT1(ADDR, PAD1, addrlen),
> > +				base + QUADSPI_LUT(lut_base));
> > +		qspi_writel(q, LUT0(DUMMY, PAD1, read_dm) |
> > +			    LUT1(FSL_READ, PAD4, rxfifo),
> > +				base + QUADSPI_LUT(lut_base + 1));
> > +	}
> >  
> >  	/* Write enable */
> >  	lut_base = SEQID_WREN * 4;
> > @@ -468,6 +478,7 @@ static int fsl_qspi_get_seqid(struct fsl_qspi *q, 
> > u8 cmd)  {
> >  	switch (cmd) {
> >  	case SPINOR_OP_READ_1_1_4:
> > +	case SPINOR_OP_READ_FAST:
> >  		return SEQID_READ;
> >  	case SPINOR_OP_WREN:
> >  		return SEQID_WREN;
> > @@ -963,6 +974,7 @@ static int fsl_qspi_probe(struct platform_device *pdev)
> >  	struct spi_nor *nor;
> >  	struct mtd_info *mtd;
> >  	int ret, i = 0;
> > +	enum read_mode mode = SPI_NOR_QUAD;
> >  
> >  	q = devm_kzalloc(dev, sizeof(*q), GFP_KERNEL);
> >  	if (!q)
> > @@ -1064,7 +1076,10 @@ static int fsl_qspi_probe(struct platform_device *pdev)
> >  		/* set the chip address for READID */
> >  		fsl_qspi_set_base_addr(q, nor);
> >  
> > -		ret = spi_nor_scan(nor, NULL, SPI_NOR_QUAD);
> > +		ret = of_property_read_bool(np, "m25p,fast-read");
> > +		mode = (ret) ? SPI_NOR_FAST : SPI_NOR_QUAD;
> > +
> > +		ret = spi_nor_scan(nor, NULL, mode);
> >  		if (ret)
> >  			goto mutex_failed;
> >  
> I understand you want to provide a more generic read mode, but this is a quad spi driver, I prefer to provide the options, either quad read/quad IO read, or just normal read.
> > --
> > 2.1.0.27.g96db324
> > 
> > 
> > ______________________________________________________
> > Linux MTD discussion mailing list
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