Re: [PATCH v3 06/23] thermal: armada: average over samples to avoid glitches

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>, Andrew Lunn <andrew@lunn.ch>,
	Jason Cooper <jason@lakedaemon.net>,
	Nadav Haklai <nadavh@marvell.com>,
	devicetree@vger.kernel.org,
	Antoine Tenart <antoine.tenart@bootlin.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Gregory Clement <gregory.clement@bootlin.com>,
	linux-pm@vger.kernel.org, Will Deacon <will.deacon@arm.com>,
	Maxime Chevallier <maxime.chevallier@bootlin.com>,
	Eduardo Valentin <edubezval@gmail.com>,
	David Sniatkiwicz <davidsn@marvell.com>,
	Rob Herring <robh+dt@kernel.org>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Zhang Rui <rui.zhang@intel.com>,
	linux-arm-kernel@lists.infradead.org,
	Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Subject: Re: [PATCH v3 06/23] thermal: armada: average over samples to avoid glitches
Date: Sun, 29 Jul 2018 21:30:55 +0200	[thread overview]
Message-ID: <20180729213055.2215bd53@xps13> (raw)
In-Reply-To: <2ab1a1f6-e0c3-3eed-a088-9b04e88fce12@linaro.org>

Hi Daniel,

Daniel Lezcano <daniel.lezcano@linaro.org> wrote on Fri, 27 Jul 2018
18:29:01 +0200:

> On 16/07/2018 16:41, Miquel Raynal wrote:
> > Configure the sample frequency and number of averaged samples.
> > 
> > This is needed for two reasons:
> > 1/ To be bootloader independent.
> > 2/ To prepare the introduction of multi-sensors support by preventing
> >    inconsistencies when reading temperatures that could be a mean of
> >    samples took from different sensors.
> > 
> > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > ---
> >  drivers/thermal/armada_thermal.c | 25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> > 
> > diff --git a/drivers/thermal/armada_thermal.c b/drivers/thermal/armada_thermal.c
> > index 9291ea3ad2f7..1f9706d96a0d 100644
> > --- a/drivers/thermal/armada_thermal.c
> > +++ b/drivers/thermal/armada_thermal.c
> > @@ -54,7 +54,12 @@
> >  #define CONTROL0_TSEN_START		BIT(0)
> >  #define CONTROL0_TSEN_RESET		BIT(1)
> >  #define CONTROL0_TSEN_ENABLE		BIT(2)
> > +#define CONTROL0_TSEN_AVG_BYPASS	BIT(6)
> > +#define CONTROL0_TSEN_OSR_SHIFT		24
> > +#define CONTROL0_TSEN_OSR_MAX		0x3
> >  
> > +#define CONTROL1_TSEN_AVG_SHIFT		0  
> 
> Why shift by zero ?
> 

I know some people do not like it, it's a matter of taste, as this IP
registers documentation is a bit fuzzy, I wanted to make it clear that
it was the first region in the CONTROL1 register. It's optimized out by
the compiler anyway.

> 
> 
> > +#define CONTROL1_TSEN_AVG_MASK		0x7
> >  #define CONTROL1_EXT_TSEN_SW_RESET	BIT(7)
> >  #define CONTROL1_EXT_TSEN_HW_RESETn	BIT(8)
> >  
> > @@ -194,6 +199,13 @@ static void armada_ap806_init(struct platform_device *pdev,
> >  	reg = readl_relaxed(priv->control0);
> >  	reg &= ~CONTROL0_TSEN_RESET;
> >  	reg |= CONTROL0_TSEN_START | CONTROL0_TSEN_ENABLE;
> > +
> > +	/* Sample every ~2ms */
> > +	reg |= CONTROL0_TSEN_OSR_MAX << CONTROL0_TSEN_OSR_SHIFT;
> > +
> > +	/* Enable average (2 samples by default) */
> > +	reg &= ~CONTROL0_TSEN_AVG_BYPASS;
> > +
> >  	writel(reg, priv->control0);
> >  
> >  	/* Wait the sensors to be valid or the core will warn the user */
> > @@ -203,7 +215,20 @@ static void armada_ap806_init(struct platform_device *pdev,
> >  static void armada_cp110_init(struct platform_device *pdev,
> >  			      struct armada_thermal_priv *priv)
> >  {
> > +	u32 reg;
> > +
> >  	armada380_init(pdev, priv);
> > +
> > +	/* Sample every ~2ms */
> > +	reg = readl_relaxed(priv->control0);
> > +	reg |= CONTROL0_TSEN_OSR_MAX << CONTROL0_TSEN_OSR_SHIFT;
> > +	writel(reg, priv->control0);
> > +
> > +	/* Average the output value over 2^1 = 2 samples */
> > +	reg = readl_relaxed(priv->control1);
> > +	reg &= ~CONTROL1_TSEN_AVG_MASK << CONTROL1_TSEN_AVG_SHIFT;
> > +	reg |= 1 << CONTROL1_TSEN_AVG_SHIFT;
> > +	writel(reg, priv->control1);
> >  }
> >  
> >  static bool armada_is_valid(struct armada_thermal_priv *priv)
> >   
> 
> 

Thanks
Miquèl

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