On Mon, Feb 08, 2010 at 20:43:27, Philby John wrote:
> Hello Sekhar,
>
> On 02/08/2010 04:05 PM, Nori, Sekhar wrote:
> >>>> +static void generic_i2c_clock_pulse(unsigned int scl_pin)
> >>>> +{
> >>>> + u16 i;
> >>>> +
> >>>> + if (scl_pin) {
> >>>> + /* Send high and low on the SCL line */
> >>>> + for (i = 0; i< 9; i++) {
> >>>> + gpio_set_value(scl_pin, 0);
> >>>> + udelay(20);
> >>>> + gpio_set_value(scl_pin, 1);
> >>>> + udelay(20);
> >>>> + }
> >>>
> >>> Before using the pins as GPIO, you would have to set the
> >>> functionality of these pins as GPIO. You had this code in
> >>> previous incarnations of this patch - not sure why it is
> >>> dropped now.
> >>>
> >>
> >> Don't seem to remember having the code in the old versions at least
> >> not in generic_i2c_clock_pulse(). The functions disable_i2c_pins() and
> >> enable_i2c_pins() were discarded as the i2c protocol spec. did not
> >> specify the need. Moreover bus recovered without it. (Tested on DM355
> >> and Dm6446).
> >
> > Yes, I was referring to the davinci_cfg_reg() calls in
> > {disable|enable}_i2c_pins() functions. Per the specification
> > of the DaVinci devices, a pin needs to be muxed as 'GPIO' if
> > it is to be used as GPIO controlled by GPIO module. It may
> > have worked on couple of devices but cannot be guaranteed to
> > work on all DaVinci devices (esp. DA8XX ones).
>
>
> I think that using davinci_cfg_reg() in generic_i2c_clock_pulse() is the
> wrong place to put it. This would require adding davinci_cfg_reg() for
> all know davinci platforms. The i2c recovery procedure is correct to
> assume that it owns the SCL line at that very moment.
>
> Instead I believe pinmuxing using davinci_cfg_reg(), should be done way
> early, just like we do for DM6446 in devices.c --> davinci_init_i2c(),
> for all other platforms. What I could do in function
> generic_i2c_clock_pulse() is, set SCL to output, and use gpio_request()
> by checking REVID2 register value (0x6) for DA8xx and 0x5 for others.
But, the pins should remain as I2C pins till you actually
hit a bus lock-up. That's when you need to convert them to GPIO
pins and start the recovery by pulsing SCL.
It you make them GPIO right at the start, they wont be usable
as I2C pins for normal transfers?
Thanks,
Sekhar
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