linux-kernel - Re: [PATCH] hwmon: (pmbus) Fix vout margin caching

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Date:   Wed, 17 Aug 2022 08:32:22 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Vincent Whitchurch <vincent.whitchurch@...s.com>
Cc:     Jean Delvare <jdelvare@...e.com>, kernel@...s.com,
        Mårten Lindahl <marten.lindahl@...s.com>,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hwmon: (pmbus) Fix vout margin caching

On Tue, Aug 16, 2022 at 04:44:14PM +0200, Vincent Whitchurch wrote:
> The code currently uses a zero margin to mean not cached, but this
> results in the cache being bypassed if the (low) margin is set to zero,
> leading to lots of unnecessary SMBus transactions in that case.  Use a
> negative value instead.
> 
> Fixes: 07fb76273db89d93 ("hwmon: (pmbus) Introduce and use cached vout margins")
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>

Applied.

Thanks,
Guenter

> ---
>  drivers/hwmon/pmbus/pmbus_core.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
> index f10bac8860fc..d06b04543fd8 100644
> --- a/drivers/hwmon/pmbus/pmbus_core.c
> +++ b/drivers/hwmon/pmbus/pmbus_core.c
> @@ -2861,7 +2861,7 @@ static int pmbus_regulator_get_low_margin(struct i2c_client *client, int page)
>  		.data = -1,
>  	};
>  
> -	if (!data->vout_low[page]) {
> +	if (data->vout_low[page] < 0) {
>  		if (pmbus_check_word_register(client, page, PMBUS_MFR_VOUT_MIN))
>  			s.data = _pmbus_read_word_data(client, page, 0xff,
>  						       PMBUS_MFR_VOUT_MIN);
> @@ -2887,7 +2887,7 @@ static int pmbus_regulator_get_high_margin(struct i2c_client *client, int page)
>  		.data = -1,
>  	};
>  
> -	if (!data->vout_high[page]) {
> +	if (data->vout_high[page] < 0) {
>  		if (pmbus_check_word_register(client, page, PMBUS_MFR_VOUT_MAX))
>  			s.data = _pmbus_read_word_data(client, page, 0xff,
>  						       PMBUS_MFR_VOUT_MAX);
> @@ -3320,6 +3320,7 @@ int pmbus_do_probe(struct i2c_client *client, struct pmbus_driver_info *info)
>  	struct pmbus_data *data;
>  	size_t groups_num = 0;
>  	int ret;
> +	int i;
>  	char *name;
>  
>  	if (!info)
> @@ -3353,6 +3354,11 @@ int pmbus_do_probe(struct i2c_client *client, struct pmbus_driver_info *info)
>  	data->currpage = -1;
>  	data->currphase = -1;
>  
> +	for (i = 0; i < ARRAY_SIZE(data->vout_low); i++) {
> +		data->vout_low[i] = -1;
> +		data->vout_high[i] = -1;
> +	}
> +
>  	ret = pmbus_init_common(client, data, info);
>  	if (ret < 0)
>  		return ret;