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

From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: Miquel Raynal <miquel.raynal@bootlin.com>,
	Gregory Clement <gregory.clement@bootlin.com>,
	Jason Cooper <jason@lakedaemon.net>, Andrew Lunn <andrew@lunn.ch>,
	Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>,
	Zhang Rui <rui.zhang@intel.com>,
	Eduardo Valentin <edubezval@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	devicetree@vger.kernel.org, linux-pm@vger.kernel.org,
	Antoine Tenart <antoine.tenart@bootlin.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Maxime Chevallier <maxime.chevallier@bootlin.com>,
	Nadav Haklai <nadavh@marvell.com>,
	David Sniatkiwicz <davidsn@marvell.com>,
	Rob Herring <robh+dt@kernel.org>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 06/23] thermal: armada: average over samples to avoid glitches
Date: Fri, 27 Jul 2018 18:29:01 +0200	[thread overview]
Message-ID: <2ab1a1f6-e0c3-3eed-a088-9b04e88fce12@linaro.org> (raw)
In-Reply-To: <20180716144206.30985-7-miquel.raynal@bootlin.com>

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 ?

> +#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)
> 

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