[U-Boot] [PATCH] spi: cadence_qspi_apb: Ensure baudrate doesn't exceed max value

[Chin Liang See]

On Sun, 2016-08-07 at 16:13 +0200, Marek Vasut wrote:
> On 08/07/2016 04:11 PM, Chin Liang See wrote:
> > On Sun, 2016-08-07 at 16:05 +0200, Marek Vasut wrote:
> > > On 08/07/2016 03:53 PM, Chin Liang See wrote:
> > > > Ensuring the baudrate divisor value doesn't exceed the max
> > > > value
> > > > in the calculation.It will be capped at max value to ensure the
> > > > correct value being written into the register.
> > > > 
> > > > Signed-off-by: Chin Liang See <clsee at altera.com>
> > > > Cc: Marek Vasut <marex at denx.de>
> > > > Cc: Jagan Teki <jteki at openedev.com>
> > > > Cc: Dinh Nguyen <dinguyen at altera.com>
> > > > ---
> > > >  drivers/spi/cadence_qspi_apb.c | 4 ++++
> > > >  1 file changed, 4 insertions(+)
> > > > 
> > > > diff --git a/drivers/spi/cadence_qspi_apb.c
> > > > b/drivers/spi/cadence_qspi_apb.c
> > > > index 1a35d55..e6a8ecb 100644
> > > > --- a/drivers/spi/cadence_qspi_apb.c
> > > > +++ b/drivers/spi/cadence_qspi_apb.c
> > > > @@ -293,6 +293,10 @@ void
> > > > cadence_qspi_apb_config_baudrate_div(void
> > > > *reg_base,
> > > >  	debug("%s: ref_clk %dHz sclk %dHz Div 0x%x\n",
> > > > __func__,
> > > >  	      ref_clk_hz, sclk_hz, div);
> > > >  
> > > > +	/* ensure the baud rate doesn't exceed the max value
> > > > */
> > > > +	if (div > CQSPI_REG_CONFIG_BAUD_MASK)
> > > > +		div = CQSPI_REG_CONFIG_BAUD_MASK;
> > > > +
> > > >  	div = (div & CQSPI_REG_CONFIG_BAUD_MASK) <<
> > > > CQSPI_REG_CONFIG_BAUD_LSB;
> > > 
> > > The capping happens here ^ already , doesn't it ?
> > 
> > I have initial thought too until someone file me a bug on this. The
> > bug
> > happen when the calculated div = 16. After and with the mask, the
> > value
> > writen to register is actually 0 (register field for baudrate
> > divisor).
> 
> So this is what the problem is all about, thanks for clarifying (and
> that should be in the commit message!). But then, you don't need the
> masking, it can be turned into reg = div <<
> CQSPI_REG_CONFIG_BAUD_LSB.

Yup, let me drop v2 then

Thanks
Chin Liang

>