linux-kernel - Re: [PATCH v2] hwmon: max31790: revise the scale to write pwm

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Message-ID: <062ac1a4-7cf2-454c-ba4f-b19695f1c2b4@roeck-us.net>
Date: Sun, 28 Apr 2024 11:30:47 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Delphine CC Chiu <Delphine_CC_Chiu@...ynn.com>
Cc: patrick@...cx.xyz, Jean Delvare <jdelvare@...e.com>,
	linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] hwmon: max31790: revise the scale to write pwm

On Tue, Apr 16, 2024 at 10:22:11AM +0800, Delphine CC Chiu wrote:
> Since the value for PWMOUT Target Duty Cycle register is a 9 bit
> left-justified value that ranges from 0 to 511 and is contained in 2
> bytes.
> 
> There is an issue that the PWM signal recorded by oscilloscope would
> not be on consistently if we set PWM to 100% to the driver.
> 
> It is because the LSB of the 9 bit would always be zero if it just
> left shift 8 bit for the value that write to PWMOUT Target Duty
> Cycle register.
> 
> Therefore, revise the scale of the value that was written to pwm input
> from 255 to 511 and modify the value to left-justified value.
> 
> Signed-off-by: Delphine CC Chiu <Delphine_CC_Chiu@...ynn.com>

Applied.

Thanks,
Guenter