Re: [PATCH 04/12] i2c: pxa: Add support for pxa910/988 & new configuration features

[Yi Zhang <yizhang@mx0a-0016f401.pphosted.com>]

On Fri, May 29, 2015 at 10:22:27PM +0200, Robert Jarzmik wrote:
> Vaibhav Hiremath <vaibhav.hiremath@linaro.org> writes:
> 
> > @@ -167,6 +184,8 @@ struct pxa_i2c {
> >  #define _ICR(i2c)	((i2c)->reg_icr)
> >  #define _ISR(i2c)	((i2c)->reg_isr)
> >  #define _ISAR(i2c)	((i2c)->reg_isar)
> > +#define _ILCR(i2c)	((i2c)->reg_ilcr)
> > +#define _IWCR(i2c)	((i2c)->reg_iwcr)
> >  
> >  /*
> >   * I2C Slave mode address
> > @@ -467,11 +486,16 @@ static void i2c_pxa_reset(struct pxa_i2c *i2c)
> >  	if (i2c->reg_isar)
> >  		writel(i2c->slave_addr, _ISAR(i2c));
> >  #endif
> > -
> Not in this patch.
> 
> >  	/* set control register values */
> >  	writel(I2C_ICR_INIT | (i2c->fast_mode ? ICR_FM : 0), _ICR(i2c));
> >  	writel(readl(_ICR(i2c)) | (i2c->high_mode ? ICR_HS : 0), _ICR(i2c));
> >  
> > +	if (i2c->ilcr)
> > +		writel(i2c->ilcr, _ILCR(i2c));
> > +	if (i2c->iwcr)
> > +		writel(i2c->iwcr, _IWCR(i2c));
> > +	udelay(2);
> This is a magical 2us. Where does it come from ?

  This delay can be removed, if writing LCR and WCR before enabling this
  i2c controller, it's safe enough; and they should not be changed when
  there is bus activity.
> 
> Cheers.
> 
> -- 
> Robert