linux-kernel - Re: [PATCH] hwmon: (pmbus/lm25066) Swap low/high current coefficients for LM5066(i)

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Date:   Wed, 22 Nov 2017 15:28:16 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Robert Lippert <roblip@...il.com>
Cc:     linux-hwmon@...r.kernel.org, jdelvare@...e.com,
        linux-kernel@...r.kernel.org, xow@...gle.com,
        Robert Lippert <rlippert@...gle.com>
Subject: Re: [PATCH] hwmon: (pmbus/lm25066) Swap low/high current
 coefficients for LM5066(i)

On Wed, Nov 22, 2017 at 02:07:28PM -0800, Robert Lippert wrote:
> The _L low-current mode coefficient values should reference the
> datasheet rows with CL=VDD but it seems were mistakenly pulled from
> the rows with CL=GND.
> 
> This causes the current/power to be reported as approximately double
> the actual value when CL=GND and half the actual value when CL=VDD.
> 

This would affect all chips supported by this driver. Hmm, and I was sure
I tested this. I'll have to dig out my hardware and confirm.

The code currently only uses bit 4 of the DEVICE_SETUP (D9h) command
to determine which current limit setting to use. Looking into the
datasheet, it looks like it also has to evaluate bit 2, and I wonder
if there is a means to determine CL if bit 2 = 0. Any idea ?
Does bit 4 report the CL pin value if bit 2 = 0 ?

Thanks,
Guenter

> Signed-off-by: Robert Lippert <rlippert@...gle.com>
> ---
>  drivers/hwmon/pmbus/lm25066.c | 24 ++++++++++++------------
>  1 file changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/hwmon/pmbus/lm25066.c b/drivers/hwmon/pmbus/lm25066.c
> index 10d17fb8f283..aa052f4449a9 100644
> --- a/drivers/hwmon/pmbus/lm25066.c
> +++ b/drivers/hwmon/pmbus/lm25066.c
> @@ -191,19 +191,19 @@ static struct __coeff lm25066_coeff[6][PSC_NUM_CLASSES + 2] = {
>  			.R = -2,
>  		},
>  		[PSC_CURRENT_IN] = {
> -			.m = 10753,
> +			.m = 5405,
>  			.R = -2,
>  		},
>  		[PSC_CURRENT_IN_L] = {
> -			.m = 5405,
> +			.m = 10753,
>  			.R = -2,
>  		},
>  		[PSC_POWER] = {
> -			.m = 1204,
> +			.m = 605,
>  			.R = -3,
>  		},
>  		[PSC_POWER_L] = {
> -			.m = 605,
> +			.m = 1204,
>  			.R = -3,
>  		},
>  		[PSC_TEMPERATURE] = {
> @@ -222,23 +222,23 @@ static struct __coeff lm25066_coeff[6][PSC_NUM_CLASSES + 2] = {
>  			.R = -2,
>  		},
>  		[PSC_CURRENT_IN] = {
> -			.m = 15076,
> -			.b = -504,
> +			.m = 7645,
> +			.b = 100,
>  			.R = -2,
>  		},
>  		[PSC_CURRENT_IN_L] = {
> -			.m = 7645,
> -			.b = 100,
> +			.m = 15076,
> +			.b = -504,
>  			.R = -2,
>  		},
>  		[PSC_POWER] = {
> -			.m = 1701,
> -			.b = -4000,
> +			.m = 861,
> +			.b = -965,
>  			.R = -3,
>  		},
>  		[PSC_POWER_L] = {
> -			.m = 861,
> -			.b = -965,
> +			.m = 1701,
> +			.b = -4000,
>  			.R = -3,
>  		},
>  		[PSC_TEMPERATURE] = {
> -- 
> 2.15.0.448.gf294e3d99a-goog
>