[U-Boot] [PATCH 2/6] power: Explicitly select pmic device's bus

[Lukasz Majewski <l.majewski@samsung.com>]

Hi Leela,

> The current pmic i2c code assumes the current i2c bus is
> the same as the pmic device's bus. There is nothing ensuring
> that to be true. Therefore, select the proper bus before performing
> a transaction.
> 
> Signed-off-by: Aaron Durbin <adurbin@chromium.org>
> Signed-off-by: Simon Glass <sjg@chromium.org>
> Signed-off-by: Leela Krishna Amudala <l.krishna@samsung.com>
> Reviewed-by: Doug Anderson <dianders@google.com>
> ---
>  drivers/power/power_i2c.c |   62
> +++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 57
> insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/power/power_i2c.c b/drivers/power/power_i2c.c
> index 47c606f..c22e01f 100644
> --- a/drivers/power/power_i2c.c
> +++ b/drivers/power/power_i2c.c
> @@ -16,9 +16,45 @@
>  #include <i2c.h>
>  #include <compiler.h>
>  
> +static int pmic_select(struct pmic *p)
> +{
> +	int ret, old_bus;
> +
> +	old_bus = i2c_get_bus_num();
> +	if (old_bus != p->bus) {
> +		debug("%s: Select bus %d\n", __func__, p->bus);
> +		ret = i2c_set_bus_num(p->bus);
> +		if (ret) {
> +			debug("%s: Cannot select pmic %s, err %d\n",
> +			      __func__, p->name, ret);
> +			return -1;
> +		}
> +	}
> +
> +	return old_bus;
> +}
> +
> +static int pmic_deselect(int old_bus)
> +{
> +	int ret;
> +
> +	if (old_bus != i2c_get_bus_num()) {
> +		ret = i2c_set_bus_num(old_bus);
> +		debug("%s: Select bus %d\n", __func__, old_bus);
> +		if (ret) {
> +			debug("%s: Cannot restore i2c bus, err %d\n",
> +			      __func__, ret);
> +			return -1;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>  int pmic_reg_write(struct pmic *p, u32 reg, u32 val)
>  {
>  	unsigned char buf[4] = { 0 };
> +	int ret, old_bus;
>  
>  	if (check_reg(p, reg))
>  		return -1;
> @@ -52,23 +88,33 @@ int pmic_reg_write(struct pmic *p, u32 reg, u32
> val) return -1;
>  	}
>  
> -	if (i2c_write(pmic_i2c_addr, reg, 1, buf, pmic_i2c_tx_num))
> +	old_bus = pmic_select(p);
> +	if (old_bus < 0)
>  		return -1;
>  
> -	return 0;
> +	ret = i2c_write(pmic_i2c_addr, reg, 1, buf, pmic_i2c_tx_num);

I'm wondering if setting the bus before each, single i2c write (when we
usually perform several writes to one device) will not be an overkill
(we search the ll_entry_count linker list each time to find max i2c
adapter names) ?

The i2c_set_bus_num() is now done at pmic_probe(), but this also
introduces overkill for "probing" each device when we want to read from
it.

As a side note - I would appreciate if you would add Stefano Babic and
me on the Cc (as we are listed at e.g. power_core.c).


> +	pmic_deselect(old_bus);
> +	return ret;
>  }
>  
>  int pmic_reg_read(struct pmic *p, u32 reg, u32 *val)
>  {
>  	unsigned char buf[4] = { 0 };
>  	u32 ret_val = 0;
> +	int ret, old_bus;
>  
>  	if (check_reg(p, reg))
>  		return -1;
>  
> -	if (i2c_read(pmic_i2c_addr, reg, 1, buf, pmic_i2c_tx_num))
> +	old_bus = pmic_select(p);
> +	if (old_bus < 0)
>  		return -1;
>  
> +	ret = i2c_read(pmic_i2c_addr, reg, 1, buf, pmic_i2c_tx_num);
> +	pmic_deselect(old_bus);
> +	if (ret)
> +		return ret;
> +
>  	switch (pmic_i2c_tx_num) {
>  	case 3:
>  		if (p->sensor_byte_order ==
> PMIC_SENSOR_BYTE_ORDER_BIG) @@ -117,9 +163,15 @@ int
> pmic_reg_update(struct pmic *p, int reg, uint regval) 
>  int pmic_probe(struct pmic *p)
>  {
> -	i2c_set_bus_num(p->bus);
> +	int ret, old_bus;
> +
> +	old_bus = pmic_select(p);
> +	if (old_bus < 0)
> +		return -1;
>  	debug("Bus: %d PMIC:%s probed!\n", p->bus, p->name);
> -	if (i2c_probe(pmic_i2c_addr)) {
> +	ret = i2c_probe(pmic_i2c_addr);
> +	pmic_deselect(old_bus);
> +	if (ret) {
>  		printf("Can't find PMIC:%s\n", p->name);
>  		return -1;
>  	}



-- 
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group