[U-Boot] [PATCH 1/4] spi: cadence_qspi: Ensure spi_calibration is run when sclk change

[Chin Liang See]

Hi,

On Thu, 2015-09-03 at 16:17 +0200, marex at denx.de wrote:
> On Thursday, September 03, 2015 at 03:41:59 PM, Chin Liang See wrote:
> > Ensuring spi_calibration is run when there is a change of sclk
> > frequency. This will ensure the qspi flash access works for high
> > sclk frequency
> > 
> > Signed-off-by: Chin Liang See <clsee at altera.com>
> > Cc: Dinh Nguyen <dinguyen at opensource.altera.com>
> > Cc: Dinh Nguyen <dinh.linux at gmail.com>
> > Cc: Marek Vasut <marex at denx.de>
> > Cc: Stefan Roese <sr at denx.de>
> > Cc: Vikas Manocha <vikas.manocha at st.com>
> > Cc: Jagannadh Teki <jteki at openedev.com>
> > Cc: Pavel Machek <pavel at denx.de>
> > ---
> >  drivers/spi/cadence_qspi.c |    8 ++++----
> >  1 files changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/spi/cadence_qspi.c b/drivers/spi/cadence_qspi.c
> > index 34a0f46..300934e 100644
> > --- a/drivers/spi/cadence_qspi.c
> > +++ b/drivers/spi/cadence_qspi.c
> > @@ -37,7 +37,7 @@ static int cadence_spi_write_speed(struct udevice *bus,
> > uint hz) }
> > 
> >  /* Calibration sequence to determine the read data capture delay register
> > */ -static int spi_calibration(struct udevice *bus)
> > +static int spi_calibration(struct udevice *bus, uint hz)
> >  {
> >  	struct cadence_spi_platdata *plat = bus->platdata;
> >  	struct cadence_spi_priv *priv = dev_get_priv(bus);
> > @@ -64,7 +64,7 @@ static int spi_calibration(struct udevice *bus)
> >  	}
> > 
> >  	/* use back the intended clock and find low range */
> > -	cadence_spi_write_speed(bus, plat->max_hz);
> > +	cadence_spi_write_speed(bus, hz);
> >  	for (i = 0; i < CQSPI_READ_CAPTURE_MAX_DELAY; i++) {
> >  		/* Disable QSPI */
> >  		cadence_qspi_apb_controller_disable(base);
> > @@ -111,7 +111,7 @@ static int spi_calibration(struct udevice *bus)
> >  	      (range_hi + range_lo) / 2, range_lo, range_hi);
> > 
> >  	/* just to ensure we do once only when speed or chip select change */
> > -	priv->qspi_calibrated_hz = plat->max_hz;
> > +	priv->qspi_calibrated_hz = hz;
> >  	priv->qspi_calibrated_cs = spi_chip_select(bus);
> > 
> >  	return 0;
> > @@ -131,7 +131,7 @@ static int cadence_spi_set_speed(struct udevice *bus,
> 
> Hi,
> 
> My impression is that the logic here should be like this:
> 
> if (hz > plat->max_hz) {
>     printf("error, freq. too high");
>     return -EINVAL;
> }
> if (priv->previous_hz != hz) /* Bus frequency changed, re-calibrate */
>     spi_calibrate(bus, hz)
> cadence_spi_write_speed(bus, priv->qspi_calibrated_hz);
> priv->previous_hz = hz;
> 
> Note that you need a new private variable, previous_hz, to hold the previous
> value of "hz". This is needed since the calibrated frequency might not be
> equal to requested frequency.
> 

I know where you coming from. 
Yah, calibration can be skipped when requested frequency same as
previous or calibrated one.
Let me add that.

> > uint hz) /* Calibration required for different SCLK speed or chip select
> > */ if (priv->qspi_calibrated_hz != plat->max_hz ||
> >  	    priv->qspi_calibrated_cs != spi_chip_select(bus)) {
> > -		err = spi_calibration(bus);
> > +		err = spi_calibration(bus, hz);
> 
> This is called after the frequency is configured in this function, this looks
> really backwards.

Yah, let me remove the old code.

Thanks
Chin Liang

> 
> >  		if (err)
> >  			return err;
> >  	}
> 
> Best regards,
> Marek Vasut