[U-Boot] [PATCH 3/3] mxc_i2c: remove setting speed at each start

[Marek Vasut]

Dear Troy Kisky,

> On 5/5/2012 2:36 PM, Marek Vasut wrote:
> > Dear Troy Kisky,
> > 
> >> On 5/5/2012 6:08 AM, Marek Vasut wrote:
> >>> Dear Troy Kisky,
> >>> 
> >>>> On 4/24/2012 8:33 PM, Troy Kisky wrote:
> >>>>> Other then being very weird, this code was also wrong.
> >>>>> For example, say I set speed to 100K. I'll read back the speed
> >>>>> as 85937. But the speed is really 85937.5, so we I reset
> >>>>> the speed to 85937, I'll get 73660.7. After a couple of transactions
> >>>>> my speed is now exactly 68750 so it will remain there.
> >>>>> 
> >>>>> Signed-off-by: Troy Kisky<troy.kisky at boundarydevices.com>
> >>>>> ---
> >>>>> 
> >>>>>     drivers/i2c/mxc_i2c.c |    6 ------
> >>>>>     1 files changed, 0 insertions(+), 6 deletions(-)
> >>>>> 
> >>>>> diff --git a/drivers/i2c/mxc_i2c.c b/drivers/i2c/mxc_i2c.c
> >>>>> index 416ffee..fc68062 100644
> >>>>> --- a/drivers/i2c/mxc_i2c.c
> >>>>> +++ b/drivers/i2c/mxc_i2c.c
> >>>>> @@ -231,12 +231,6 @@ int i2c_imx_start(void)
> >>>>> 
> >>>>>     	struct mxc_i2c_regs *i2c_regs = (struct mxc_i2c_regs *)I2C_BASE;
> >>>>>     	unsigned int temp = 0;
> >>>>>     	int result;
> >>>>> 
> >>>>> -	int speed = i2c_get_bus_speed();
> >>>>> -	u8 clk_idx = i2c_imx_get_clk(speed);
> >>>>> -	u8 idx = i2c_clk_div[clk_idx][1];
> >>>>> -
> >>>>> -	/* Store divider value */
> >>>>> -	writeb(idx,&i2c_regs->ifdr);
> >>>>> 
> >>>>>     	/* Enable I2C controller */
> >>>>>     	writeb(0,&i2c_regs->i2sr);
> >>>> 
> >>>> Marek would you care to ack/nak this? It is deleting code that you
> >>>> added.
> >>> 
> >>> Ok, who will set the controller speed if you remove this?
> >> 
> >> i2c_init is the only function that writes the ifdr register after this
> >> patch.
> > 
> > And i2c_init() is called on every boot. Correct?
> > 
> >> This is fine because this register is not affected by a software reset.
> > 
> > I take it you verified this or that you're sure here :)
> 
> I haven't looked at every reference manual, but if some oddball chip
> needs it reinitialized after
> a software reset, then the fix should go into the i2c_reset function,
> not i2c_imx_start.
> And this patch would not be introducing a regression for the oddball
> chip anyway.

Agreed, I think I already acked this, sorry for the delay :)

> 
> Troy

Best regards,
Marek Vasut