[U-Boot] [PATCH] mxc_spi: Round up clock divider

[Benoît Thébaudeau]

Hi Stefano,

On 08/11/2012 12:37, Stefano Babic wrote:
> On 10/08/2012 20:51, Benoît Thébaudeau wrote:
> > Since the input frequency of the API is a maximum that should not
> > be exceeded in
> > order for the devices to operate properly, the SPI clock divider
> > should be
> > rounded up, not truncated.
> > 
> 
> Hi Benoît,
> 
> > Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau at advansee.com>
> > Cc: Wolfgang Denk <wd at denx.de>
> > Cc: Stefano Babic <sbabic at denx.de>
> > ---
> >  .../drivers/spi/mxc_spi.c                          |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git u-boot-4d3c95f.orig/drivers/spi/mxc_spi.c
> > u-boot-4d3c95f/drivers/spi/mxc_spi.c
> > index 2e15318..cf1462f 100644
> > --- u-boot-4d3c95f.orig/drivers/spi/mxc_spi.c
> > +++ u-boot-4d3c95f/drivers/spi/mxc_spi.c
> > @@ -96,7 +96,7 @@ static s32 spi_cfg_mxc(struct mxc_spi_slave
> > *mxcs, unsigned int cs,
> >  
> >  	clk_src = mxc_get_clock(MXC_CSPI_CLK);
> >  
> > -	div = clk_src / max_hz;
> > +	div = DIV_ROUND_UP(clk_src, max_hz);
> >  	div = get_cspi_div(div);
> >  
> >  	debug("clk %d Hz, div %d, real clk %d Hz\n",
> > @@ -147,7 +147,7 @@ static s32 spi_cfg_mxc(struct mxc_spi_slave
> > *mxcs, unsigned int cs,
> >  	 * The following computation is taken directly from Freescale's
> >  	 code.
> >  	 */
> >  	if (clk_src > max_hz) {
> > -		pre_div = clk_src / max_hz;
> > +		pre_div = DIV_ROUND_UP(clk_src, max_hz);
> >  		if (pre_div > 16) {
> >  			post_div = pre_div / 16;
> >  			pre_div = 15;
> > 
> 
> Agree - do you also get a case where the divider was too low and the
> SPI
> does not work or it was only examining the code ?

It was only examining the code. I had many clock issues on i.MX51, so I made a
global review of clock usage that led to that. Most i.MX5 clock functions are
broken. I have a series fixing these that I will post next week.

> Acked-by: Stefano Babic <sbabic at denx.de>
> 
> Best regards,
> Stefano Babic

Best regards,
Benoît