linux-kernel - Re: [RFC PATCH 6/8] misc: emif: add interrupt and temperature handling

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Date:	Thu, 16 Feb 2012 16:11:34 +0530
From:	Santosh Shilimkar <santosh.shilimkar@...com>
To:	Aneesh V <aneesh@...com>
CC:	linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org
Subject: Re: [RFC PATCH 6/8] misc: emif: add interrupt and temperature handling

On Saturday 04 February 2012 05:46 PM, Aneesh V wrote:
> Add an ISR for EMIF that:
> 	1. reports details of access errors
> 	2. takes action on thermal events
> 
> On thermal events SDRAM timing parameters are
> adjusted to ensure safe operation
> 
> Also clear all interrupts on shut-down. Pending IRQs
> may casue problems during warm-reset.
> 
Add some more details like MR4, EMIF polling frequency etc
for better understanding.

> Signed-off-by: Aneesh V <aneesh@...com>
> ---
>  drivers/misc/emif.c |  209 ++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 files changed, 207 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/misc/emif.c b/drivers/misc/emif.c
> index 36ba6f4..5c2b0ae 100644
> --- a/drivers/misc/emif.c
> +++ b/drivers/misc/emif.c
> @@ -500,6 +500,45 @@ static u32 get_pwr_mgmt_ctrl(u32 freq, struct emif_data *emif, u32 ip_rev)
>  }
>  
>  /*
> + * Get the temperature level of the EMIF instance:
> + * Reads the MR4 register of attached SDRAM parts to find out the temperature
> + * level. If there are two parts attached(one on each CS), then the temperature
> + * level for the EMIF instance is the higher of the two temperatures.
> + */
> +static void get_temperature_level(struct emif_data *emif)
> +{
> +	u32		temp, temperature_level;
> +	unsigned long	irqs;
> +	void __iomem	*base;
> +
> +	base = emif->base;
> +
> +	/* Read mode register 4 */
> +	writel(DDR_MR4, base + EMIF_LPDDR2_MODE_REG_CONFIG);
> +	temperature_level = readl(base + EMIF_LPDDR2_MODE_REG_DATA);
> +	temperature_level = (temperature_level & MR4_SDRAM_REF_RATE_MASK) >>
> +				MR4_SDRAM_REF_RATE_SHIFT;
> +
> +	if (emif->plat_data->device_info->cs1_used) {
> +		writel(DDR_MR4 | CS_MASK, base + EMIF_LPDDR2_MODE_REG_CONFIG);
> +		temp = readl(base + EMIF_LPDDR2_MODE_REG_DATA);
> +		temp = (temp & MR4_SDRAM_REF_RATE_MASK)
> +				>> MR4_SDRAM_REF_RATE_SHIFT;
> +		temperature_level = max(temp, temperature_level);
> +	}
> +
> +	spin_lock_irqsave(&emif->lock, irqs);
Add a line here.
> +	/* treat everything less than nominal(3) in MR4 as nominal */
> +	if (unlikely(temperature_level < SDRAM_TEMP_NOMINAL))
> +		temperature_level = SDRAM_TEMP_NOMINAL;
> +
> +	/* if we get reserved value in MR4 persist with the existing value */
> +	if (likely(temperature_level != SDRAM_TEMP_RESERVED_4))
> +		emif->temperature_level = temperature_level;
> +	spin_unlock_irqrestore(&emif->lock, irqs);
> +}
> +

rest of the patch looks fine to me
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