linux-kernel - Re: [RFC PATCH v2 2/4] hwmon: (jc42) Convert to regmap's built-in caching

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Date:   Thu, 20 Oct 2022 15:04:47 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     linux-hwmon@...r.kernel.org, jdelvare@...e.com,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 2/4] hwmon: (jc42) Convert to regmap's built-in
 caching

On Thu, Oct 20, 2022 at 11:03:18PM +0200, Martin Blumenstingl wrote:
> Move over to regmap's built-in caching instead of adding a custom
> caching implementation. This works for JC42_REG_TEMP_UPPER,
> JC42_REG_TEMP_LOWER and JC42_REG_TEMP_CRITICAL as these values never
> change except when explicitly written. For JC42_REG_TEMP a cache
> variable is still kept as regmap cannot cache this register (because
> it's volatile, meaning it can change at any time).
> 

Just drop that one as well, together with jc42_update_device(),
and read the temperature directly where needed. In practice
caching of 'hot' registers isn't really worth the trouble.

Thanks,
Guenter

> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> ---
>  drivers/hwmon/jc42.c | 97 ++++++++++++++++++++++++--------------------
>  1 file changed, 54 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/hwmon/jc42.c b/drivers/hwmon/jc42.c
> index 329a80264556..3f524ab5451c 100644
> --- a/drivers/hwmon/jc42.c
> +++ b/drivers/hwmon/jc42.c
> @@ -200,21 +200,6 @@ static struct jc42_chips jc42_chips[] = {
>  	{ STM_MANID, STTS3000_DEVID, STTS3000_DEVID_MASK },
>  };
>  
> -enum temp_index {
> -	t_input = 0,
> -	t_crit,
> -	t_min,
> -	t_max,
> -	t_num_temp
> -};
> -
> -static const u8 temp_regs[t_num_temp] = {
> -	[t_input] = JC42_REG_TEMP,
> -	[t_crit] = JC42_REG_TEMP_CRITICAL,
> -	[t_min] = JC42_REG_TEMP_LOWER,
> -	[t_max] = JC42_REG_TEMP_UPPER,
> -};
> -
>  /* Each client has this additional data */
>  struct jc42_data {
>  	struct regmap	*regmap;
> @@ -224,7 +209,7 @@ struct jc42_data {
>  	unsigned long	last_updated;	/* In jiffies */
>  	u16		orig_config;	/* original configuration */
>  	u16		config;		/* current configuration */
> -	u16		temp[t_num_temp];/* Temperatures */
> +	u16		temp;		/* Cached temperature register value */