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Date: Mon, 3 Jun 2024 22:31:50 +1000
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Subject: Re: [PATCH RFT v3 3/4] hwmon: (spd5118) Add suspend/resume support
To: Guenter Roeck <linux@roeck-us.net>, linux-hwmon@vger.kernel.org
Cc: devicetree@vger.kernel.org, Rob Herring <robh@kernel.org>,
 Krzysztof Kozlowski <krzk+dt@kernel.org>, Conor Dooley
 <conor+dt@kernel.org>, linux-kernel@vger.kernel.org,
 Armin Wolf <W_Armin@gmx.de>, =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?=
 <linux@weissschuh.net>, =?UTF-8?Q?Ren=C3=A9_Rebe?= <rene@exactcode.de>,
 Wolfram Sang <wsa+renesas@sang-engineering.com>
References: <20240531230556.1409532-1-linux@roeck-us.net>
 <20240531230556.1409532-4-linux@roeck-us.net>
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From: Stephen Horvath <s.horvath@outlook.com.au>
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Hi,

On 1/6/24 09:05, Guenter Roeck wrote:
> Add suspend/resume support to ensure that limit and configuration
> registers are updated and synchronized after a suspend/resume cycle.
> 
> Cc: Armin Wolf <W_Armin@gmx.de>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
> v3: No change
> 
> v2: New patch
> 
> RFT: I tested the patch through a suspend/resume cycle, and it seems
>       to work, but I am not sure if that had any effect because,
>       after all, the memory is still active during suspend/resume.
>       I was unable to test a hibernation cycle with my system.
> 

For me, the driver just reports 0°C after suspend/resume, but works fine 
beforehand, tested on both my desktop and laptop, with kernel 6.9.3 and 
6.10.0-rc2 (on the laptop only).

Hibernation does seem to work fine though (at least on 6.9.3).

>   drivers/hwmon/spd5118.c | 29 +++++++++++++++++++++++++++++
>   1 file changed, 29 insertions(+)
> 
> diff --git a/drivers/hwmon/spd5118.c b/drivers/hwmon/spd5118.c
> index d3fc0ae17743..baa315172298 100644
> --- a/drivers/hwmon/spd5118.c
> +++ b/drivers/hwmon/spd5118.c
> @@ -20,6 +20,7 @@
>   #include <linux/i2c.h>
>   #include <linux/hwmon.h>
>   #include <linux/module.h>
> +#include <linux/pm.h>
>   #include <linux/regmap.h>
>   #include <linux/units.h>
>   
> @@ -432,6 +433,8 @@ static int spd5118_probe(struct i2c_client *client)
>   	if (!spd5118_vendor_valid(bank, vendor))
>   		return -ENODEV;
>   
> +	dev_set_drvdata(dev, regmap);
> +
>   	hwmon_dev = devm_hwmon_device_register_with_info(dev, "spd5118",
>   							 regmap, &spd5118_chip_info,
>   							 NULL);
> @@ -449,6 +452,31 @@ static int spd5118_probe(struct i2c_client *client)
>   	return 0;
>   }
>   
> +static int spd5118_suspend(struct device *dev)
> +{
> +	struct regmap *regmap = dev_get_drvdata(dev);
> +
> +	regcache_cache_bypass(regmap, true);
> +	regmap_update_bits(regmap, SPD5118_REG_TEMP_CONFIG, SPD5118_TS_DISABLE,
> +			   SPD5118_TS_DISABLE);
> +	regcache_cache_bypass(regmap, false);
> +
> +	regcache_cache_only(regmap, true);
> +	regcache_mark_dirty(regmap);
> +
> +	return 0;
> +}
> +
> +static int spd5118_resume(struct device *dev)
> +{
> +	struct regmap *regmap = dev_get_drvdata(dev);
> +
> +	regcache_cache_only(regmap, false);

Adding something like this fixes the readings after resume for me:

	regmap_update_bits(regmap, SPD5118_REG_TEMP_CONFIG, SPD5118_TS_DISABLE, 0);

But that was just the naive solution I thought of.

> +	return regcache_sync(regmap);
> +}
> +
> +static DEFINE_SIMPLE_DEV_PM_OPS(spd5118_pm_ops, spd5118_suspend, spd5118_resume);
> +
>   static const struct i2c_device_id spd5118_id[] = {
>   	{ "spd5118", 0 },
>   	{ }
> @@ -466,6 +494,7 @@ static struct i2c_driver spd5118_driver = {
>   	.driver = {
>   		.name	= "spd5118",
>   		.of_match_table = spd5118_of_ids,
> +		.pm = pm_sleep_ptr(&spd5118_pm_ops),
>   	},
>   	.probe		= spd5118_probe,
>   	.id_table	= spd5118_id,


For reference: I believe both my devices also have Montage Technology 
M88SPD5118 chips; the desktop has Kingston KF560C36-32 RAM, the laptop 
has Crucial CT16G56C46S5.

Thanks,
Steve