[U-Boot] [PATCH] 7/12 Multiadapter/multibus I2C, drivers part 4

[Heiko Schocher]

Hello ksi,

Heiko Schocher schrieb:
> Hello ksi,
> 
> ksi at koi8.net wrote:
>> On Mon, 16 Feb 2009, Wolfgang Denk wrote:
>>
>>> Dear ksi at koi8.net,
>>>
>>> In message <Pine.LNX.4.64ksi.0902142019520.6240 at home-gw.koi8.net> you wrote:
> [...]
>>>> And remember, the devil is in details. How are you going to assign
>>>> (initialize) that innocent looking "cur_adap_nr->hwadapnr"? How are you
>>>> going to work on an adapter other that "current" in a situation when you can
>>>> NOT change "current" adapter (e.g. perform all I2C layer initialization
>>>> while still running from flash?) Remember, this is plain C and there is no
>>> What makes you insist that we cannot change a variable if we need to
>>> be able to change one?
>> It is NOT just variable. My approach uses i2c _BUS_, not _ADAPTER_. And
>> number of busses can be bigger than number of adapters (e.g. when some
>> busses a reached via muxes or switches.) When doing i2c_set_current_bus()
>> you are switching _NOT_ adapters, but busses. That involves not only
>> changing that global variable but also reprogramming muxes/switches for
>> i2c_set_current_bus() to be consistent and hardware independent. Otherwise
> 
> You have no i2c_set_current_bus() in your code! I think you mean
> i2c_set_current_bus(), right?
> 
> And this function fails when running from flash! So, how can you switch
> busses with your patches when running from flash?
> 
> Here your function:
> 
> int i2c_set_bus_num(unsigned int bus)
> {
> #ifndef CONFIG_SYS_I2C_DIRECT_BUS
>         int             i;
>         u_int8_t        buf;
> #endif
> 
>         if ((bus >= CONFIG_SYS_NUM_I2C_BUSSES) || !(gd->flags & GD_FLG_RELOC))
>                 return(-1);
> [...]
> 
> This function wouldn;t work from flash ...

And one more reason, why your function will not work from flash:

later in your i2c_set_bus_num function:
[...]
        if ((i2c_bus[i2c_cur_bus].next_hop[0].chip != 0) &&
                        (ADAP(i2c_cur_bus)->init_done != 0)) {

You only switch muxes if init_done != 0 ... but init_done is
not writeable when running from flash, so it is "= 0" when
code is not relocated ... how work this for you?

But this can be solved, if we always init the hardwareadapter
when switching to it and running from flash ... and if we are
relocated, we can analyse this flag, if init_done = 0, we init
this hardware adapter ...

My proposal for the i2c_set_bus_num(unsigned int bus) function:

int i2c_set_bus_num(unsigned int bus)
{
#ifndef CONFIG_SYS_I2C_DIRECT_BUS
	int		i;
	u_int8_t	buf;
#endif

	if (bus >= CONFIG_SYS_NUM_I2C_BUSSES)
		return(-1);

#ifndef CONFIG_SYS_I2C_DIRECT_BUS
	/* Disconnect current bus (turn off muxes if any) */
	if ((i2c_bus[i2c_cur_bus].next_hop[0].chip != 0) &&
			(ADAP(i2c_cur_bus)->init_done != 0)) {

		i = CONFIG_SYS_I2C_MAX_HOPS;

		do {
			u_int8_t	chip;
			
			if ((chip = i2c_bus[i2c_cur_bus].next_hop[--i].chip) == 0)
				continue;

			ADAP(i2c_cur_bus)->write(chip, 0, 0, &buf, 1);

		} while (i > 0);
	}
#endif

	cur_adap_nr = (i2c_adap_t *)&ADAP(bus);
	if (ADAP(bus)->init_done == 0) {
		i2c_init_bus(bus, ADAP(bus)->speed, ADAP(bus)->slaveaddr);
	}

#ifndef CONFIG_SYS_I2C_DIRECT_BUS
	/* Connect requested bus if behind muxes */
	if (i2c_bus[bus].next_hop[0].chip != 0) {

		/* Set all muxes along the path to that bus */
		for (i = 0; i < CONFIG_SYS_I2C_MAX_HOPS; i++) {

			if (i2c_bus[bus].next_hop[i].chip == 0) break;

			i2c_mux_set(i2c_bus[bus].adapter,
					i2c_bus[bus].next_hop[i].mux.id,
					i2c_bus[bus].next_hop[i].chip,
					i2c_bus[bus].next_hop[i].channel);
		}
	}
#endif

	i2c_cur_bus = bus;
	return(0);
}

This function should also work, when running from flash. + a hardware adapter
is only initialized when we switch to it, so no need to initialize all
hardwareadapters somewhere ...
(requirement: cur_adap_nr, i2c_cur_bus is writeable when running in flash)

bye
Heiko
-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
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