[U-Boot] [PATCH] driver: fsl_qspi: disable AHB buffer prefetch

[Yunhui Cui]

>On 07/07/2016 1:01 AM, york sun wrote: 
> On 07/03/2016 08:27 PM, Yunhui Cui wrote:
> > From: Yunhui Cui <yunhui.cui at nxp.com>
> >
> > A-009282: QuadSPI: QuadSPI data pre-fetch can result in incorrect data
> > Affects: QuadSPI
> > Description: With AHB buffer prefetch enabled, the QuadSPI may return
> > incorrect data on the AHB interface. The buffer pre-fetch is enabled
> > if the fetch size as configured either in the LUT or in the BUFxCR
> > register is greater than 8 bytes.
> > Impact: Only 64 bit read allowed.
> > Workaround: Keep the read data size to 64 bits (8 Bytes), which
> > disables the prefetch on the AHB buffer, and prevents this issue from
> > occurring.
> >
> > Signed-off-by: Yunhui Cui <yunhui.cui at nxp.com>
> > ---
> >   drivers/spi/fsl_qspi.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/spi/fsl_qspi.c b/drivers/spi/fsl_qspi.c index
> > 75cbab2..e0a002d 100644
> > --- a/drivers/spi/fsl_qspi.c
> > +++ b/drivers/spi/fsl_qspi.c
> > @@ -444,7 +444,7 @@ static void qspi_init_ahb_read(struct fsl_qspi_priv
> *priv)
> >   	qspi_write32(priv->flags, &regs->buf1cr,
> QSPI_BUFXCR_INVALID_MSTRID);
> >   	qspi_write32(priv->flags, &regs->buf2cr,
> QSPI_BUFXCR_INVALID_MSTRID);
> >   	qspi_write32(priv->flags, &regs->buf3cr, QSPI_BUF3CR_ALLMST_MASK |
> > -		     (0x80 << QSPI_BUF3CR_ADATSZ_SHIFT));
> > +		     (0x1 << QSPI_BUF3CR_ADATSZ_SHIFT));
> >
> >   	/* We only use the buffer3 */
> >   	qspi_write32(priv->flags, &regs->buf0ind, 0);
> >
> 
> Yunhui,
> 
> We handle erratum workaround using macros in case the workaround has
> impact on other SoCs.

[Yunhui] For now, all SoCs with Qspi module need this errata.

> We also put the erratum information either in a
> README file, or inline comment. It will be easier to read the code later.

[Yunhui] ok, I will add inline comment in next version.

> You don't have to put the whole erratum description in the commit message,
> as long as it explains what this patch does and refer the erratum number
> somewhere in the message so we can search the git log.
> 
> York

[Yunhui] ok, I will update the commit message in next version.

Thanks
Yunhui