Re: [PATCH 1/1] OMAP: I2C: Add mpu wake up latency constraint in i2c

[Kevin Hilman <khilman@deeprootsystems.com>]

Kalle Jokiniemi <kalle.jokiniemi@digia.com> writes:

> While waiting for completion of the i2c transfer, the
> MPU could hit OFF mode and cause several msecs of
> delay that made i2c transfers fail more often. The
> extra delays and subsequent re-trys cause i2c clocks
> to be active more often. This has also an negative
> effect on power consumption.
>
> Added a constraint that allows MPU to wake up in few
> hundred usecs, which is roughly the average i2c wait
> period.
>
> The constraint function is passed as platform data from
> plat-omap/i2c.c and applied only on OMAP34XX devices.

Seems like the latency value should also be (optionally) passed in
pdata so this can be experimented with per-platform.

Other than that looks ok to me.

Do we have an official OMAP I2C maintainer who should signoff on this?

Kevin


> Signed-off-by: Kalle Jokiniemi <kalle.jokiniemi@digia.com>
> ---
>  arch/arm/plat-omap/i2c.c      |   49 +++++++++++++++++++++++++++++++----------
>  drivers/i2c/busses/i2c-omap.c |   17 +++++++++++---
>  include/linux/i2c-omap.h      |    9 +++++++
>  3 files changed, 59 insertions(+), 16 deletions(-)
>  create mode 100644 include/linux/i2c-omap.h
>
> diff --git a/arch/arm/plat-omap/i2c.c b/arch/arm/plat-omap/i2c.c
> index 8b84839..d43d0ad 100644
> --- a/arch/arm/plat-omap/i2c.c
> +++ b/arch/arm/plat-omap/i2c.c
> @@ -26,8 +26,10 @@
>  #include <linux/kernel.h>
>  #include <linux/platform_device.h>
>  #include <linux/i2c.h>
> +#include <linux/i2c-omap.h>
>  #include <mach/irqs.h>
>  #include <mach/mux.h>
> +#include <mach/omap-pm.h>
>  
>  #define OMAP_I2C_SIZE		0x3f
>  #define OMAP1_I2C_BASE		0xfffb3800
> @@ -69,14 +71,14 @@ static struct resource i2c_resources[][2] = {
>  		},					\
>  	}
>  
> -static u32 i2c_rate[ARRAY_SIZE(i2c_resources)];
> +static struct omap_i2c_bus_platform_data i2c_pdata[ARRAY_SIZE(i2c_resources)];
>  static struct platform_device omap_i2c_devices[] = {
> -	I2C_DEV_BUILDER(1, i2c_resources[0], &i2c_rate[0]),
> +	I2C_DEV_BUILDER(1, i2c_resources[0], &i2c_pdata[0]),
>  #if	defined(CONFIG_ARCH_OMAP24XX) || defined(CONFIG_ARCH_OMAP34XX)
> -	I2C_DEV_BUILDER(2, i2c_resources[1], &i2c_rate[1]),
> +	I2C_DEV_BUILDER(2, i2c_resources[1], &i2c_pdata[1]),
>  #endif
>  #if	defined(CONFIG_ARCH_OMAP34XX)
> -	I2C_DEV_BUILDER(3, i2c_resources[2], &i2c_rate[2]),
> +	I2C_DEV_BUILDER(3, i2c_resources[2], &i2c_pdata[2]),
>  #endif
>  };
>  
> @@ -100,6 +102,25 @@ static const int omap34xx_pins[][2] = {};
>  
>  #define OMAP_I2C_CMDLINE_SETUP	(BIT(31))
>  
> +/**
> + * omap_i2c_set_wfc_mpu_wkup_lat - sets mpu wake up constraint
> + * @dev:	i2c bus device pointer
> + * @set:	set or clear constraints
> + *
> + * When waiting for completion of a i2c transfer, we need to set a wake up
> + * latency constraint for the MPU. This is to ensure quick enough wakeup
> + * from idle, when transfer completes.
> + */
> +#ifdef CONFIG_ARCH_OMAP34XX
> +static void omap_i2c_set_wfc_mpu_wkup_lat(struct device *dev, int set)
> +{
> +	omap_pm_set_max_mpu_wakeup_lat(dev, set ? 500 : -1);
> +}
> +#else
> +static inline void omap_i2c_set_wfc_mpu_wkup_lat(struct device *dev, int set)
> +{; }
> +#endif
> +
>  static void __init omap_i2c_mux_pins(int bus)
>  {
>  	int scl, sda;
> @@ -180,8 +201,8 @@ static int __init omap_i2c_bus_setup(char *str)
>  	get_options(str, 3, ints);
>  	if (ints[0] < 2 || ints[1] < 1 || ints[1] > ports)
>  		return 0;
> -	i2c_rate[ints[1] - 1] = ints[2];
> -	i2c_rate[ints[1] - 1] |= OMAP_I2C_CMDLINE_SETUP;
> +	i2c_pdata[ints[1] - 1].clkrate = ints[2];
> +	i2c_pdata[ints[1] - 1].clkrate |= OMAP_I2C_CMDLINE_SETUP;
>  
>  	return 1;
>  }
> @@ -195,9 +216,11 @@ static int __init omap_register_i2c_bus_cmdline(void)
>  {
>  	int i, err = 0;
>  
> -	for (i = 0; i < ARRAY_SIZE(i2c_rate); i++)
> -		if (i2c_rate[i] & OMAP_I2C_CMDLINE_SETUP) {
> -			i2c_rate[i] &= ~OMAP_I2C_CMDLINE_SETUP;
> +	for (i = 0; i < ARRAY_SIZE(i2c_pdata); i++)
> +		if (i2c_pdata[i].clkrate & OMAP_I2C_CMDLINE_SETUP) {
> +			i2c_pdata[i].clkrate &= ~OMAP_I2C_CMDLINE_SETUP;
> +			i2c_pdata[i].set_mpu_wkup_lat =
> +						omap_i2c_set_wfc_mpu_wkup_lat;
>  			err = omap_i2c_add_bus(i + 1);
>  			if (err)
>  				goto out;
> @@ -231,9 +254,11 @@ int __init omap_register_i2c_bus(int bus_id, u32 clkrate,
>  			return err;
>  	}
>  
> -	if (!i2c_rate[bus_id - 1])
> -		i2c_rate[bus_id - 1] = clkrate;
> -	i2c_rate[bus_id - 1] &= ~OMAP_I2C_CMDLINE_SETUP;
> +	if (!i2c_pdata[bus_id - 1].clkrate)
> +		i2c_pdata[bus_id - 1].clkrate = clkrate;
> +
> +	i2c_pdata[bus_id - 1].set_mpu_wkup_lat = omap_i2c_set_wfc_mpu_wkup_lat;
> +	i2c_pdata[bus_id - 1].clkrate &= ~OMAP_I2C_CMDLINE_SETUP;
>  
>  	return omap_i2c_add_bus(bus_id);
>  }
> diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> index 75bf3ad..da6d276 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -37,6 +37,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/clk.h>
>  #include <linux/io.h>
> +#include <linux/i2c-omap.h>
>  
>  /* I2C controller revisions */
>  #define OMAP_I2C_REV_2			0x20
> @@ -165,6 +166,8 @@ struct omap_i2c_dev {
>  	struct clk		*fclk;		/* Functional clock */
>  	struct completion	cmd_complete;
>  	struct resource		*ioarea;
> +	void			(*set_mpu_wkup_lat)(struct device *dev,
> +						    int set);
>  	u32			speed;		/* Speed of bus in Khz */
>  	u16			cmd_err;
>  	u8			*buf;
> @@ -526,8 +529,10 @@ static int omap_i2c_xfer_msg(struct i2c_adapter *adap,
>  	 * REVISIT: We should abort the transfer on signals, but the bus goes
>  	 * into arbitration and we're currently unable to recover from it.
>  	 */
> +	dev->set_mpu_wkup_lat(dev->dev, 1);
>  	r = wait_for_completion_timeout(&dev->cmd_complete,
>  					OMAP_I2C_TIMEOUT);
> +	dev->set_mpu_wkup_lat(dev->dev, 0);
>  	dev->buf_len = 0;
>  	if (r < 0)
>  		return r;
> @@ -844,6 +849,7 @@ omap_i2c_probe(struct platform_device *pdev)
>  	struct omap_i2c_dev	*dev;
>  	struct i2c_adapter	*adap;
>  	struct resource		*mem, *irq, *ioarea;
> +	struct omap_i2c_bus_platform_data *pdata = pdev->dev.platform_data;
>  	irq_handler_t isr;
>  	int r;
>  	u32 speed = 0;
> @@ -873,10 +879,13 @@ omap_i2c_probe(struct platform_device *pdev)
>  		goto err_release_region;
>  	}
>  
> -	if (pdev->dev.platform_data != NULL)
> -		speed = *(u32 *)pdev->dev.platform_data;
> -	else
> -		speed = 100;	/* Defualt speed */
> +	if (pdata != NULL) {
> +		speed = pdata->clkrate;
> +		dev->set_mpu_wkup_lat = pdata->set_mpu_wkup_lat;
> +	} else {
> +		speed = 100;	/* Default speed */
> +		dev->set_mpu_wkup_lat = NULL;
> +	}
>  
>  	dev->speed = speed;
>  	dev->idle = 1;
> diff --git a/include/linux/i2c-omap.h b/include/linux/i2c-omap.h
> new file mode 100644
> index 0000000..1362fba
> --- /dev/null
> +++ b/include/linux/i2c-omap.h
> @@ -0,0 +1,9 @@
> +#ifndef __I2C_OMAP_H__
> +#define __I2C_OMAP_H__
> +
> +struct omap_i2c_bus_platform_data {
> +	u32		clkrate;
> +	void		(*set_mpu_wkup_lat)(struct device *dev, int set);
> +};
> +
> +#endif
> -- 
> 1.5.4.3