Re: [PATCH] I2C: OMAP3: PM: (re)init for every transfer to support off-mode

[Ben Dooks <ben-linux@fluff.org>]

On Tue, Jul 21, 2009 at 04:09:03PM -0700, Kevin Hilman wrote:
> From: Rajendra Nayak <rnayak@ti.com>
> 
> Because of OMAP off-mode, powerdomain can go off when I2C is idle.
> Save enough state, and do a re-init for each transfer.
> 
> Additional save/restore state added by Jagadeesh Bhaskar Pakaravoor
> (SYSC_REG) and Aaro Koskinen (wakeup sources.)
> 
> Also, The OMAP3430 TRM states:
> 
> "During active mode (I2Ci.I2C_CON[15] I2C_EN bit is set to 1), make no
> changes to the I2Ci.I2C_SCLL and I2Ci.I2C_SCLH registers.  Changes may
> result in unpredictable behavior."
> 
> Hence, the I2C_EN bit should be clearer when modifying these
> registers. Please note that clearing the entire I2C_CON register to
> disable the I2C module is safe, because the I2C_CON register is
> re-configured for each transfer.

should this be applied as a bugfix, or kept for next merge window?
 
> Signed-off-by: Jouni Hogander <jouni.hogander@nokia.com>
> Signed-off-by: Rajendra Nayak <rnayak@ti.com>
> Cc: Jagadeesh Bhaskar Pakaravoor <j-pakaravoor@ti.com>
> Cc: Aaro Koskinen <aaro.koskinen@nokia.com>
> Cc: Jon Hunter <jon-hunter@ti.com>
> Cc: Hu Tao <taohu@motorola.com>
> Cc: Xiaolong Chen <A21785@motorola.com>
> Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
> ---
> This patch has been tested extensively as part of the OMAP 'PM branch'
> 
>  drivers/i2c/busses/i2c-omap.c |   64 ++++++++++++++++++++++++++--------------
>  1 files changed, 41 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> index ad8d201..bb8ae50 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -178,6 +178,12 @@ struct omap_i2c_dev {
>  	unsigned		b_hw:1;		/* bad h/w fixes */
>  	unsigned		idle:1;
>  	u16			iestate;	/* Saved interrupt register */
> +	u16			pscstate;
> +	u16			scllstate;
> +	u16			sclhstate;
> +	u16			bufstate;
> +	u16			syscstate;
> +	u16			westate;
>  };
>  
>  static inline void omap_i2c_write_reg(struct omap_i2c_dev *i2c_dev,
> @@ -230,9 +236,18 @@ static void omap_i2c_unidle(struct omap_i2c_dev *dev)
>  
>  	clk_enable(dev->iclk);
>  	clk_enable(dev->fclk);
> +	if (cpu_is_omap34xx()) {
> +		omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, 0);
> +		omap_i2c_write_reg(dev, OMAP_I2C_PSC_REG, dev->pscstate);
> +		omap_i2c_write_reg(dev, OMAP_I2C_SCLL_REG, dev->scllstate);
> +		omap_i2c_write_reg(dev, OMAP_I2C_SCLH_REG, dev->sclhstate);
> +		omap_i2c_write_reg(dev, OMAP_I2C_BUF_REG, dev->bufstate);
> +		omap_i2c_write_reg(dev, OMAP_I2C_SYSC_REG, dev->syscstate);
> +		omap_i2c_write_reg(dev, OMAP_I2C_WE_REG, dev->westate);
> +		omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, OMAP_I2C_CON_EN);
> +	}
>  	dev->idle = 0;
> -	if (dev->iestate)
> -		omap_i2c_write_reg(dev, OMAP_I2C_IE_REG, dev->iestate);
> +	omap_i2c_write_reg(dev, OMAP_I2C_IE_REG, dev->iestate);
>  }
>  
>  static void omap_i2c_idle(struct omap_i2c_dev *dev)
> @@ -258,7 +273,7 @@ static void omap_i2c_idle(struct omap_i2c_dev *dev)
>  
>  static int omap_i2c_init(struct omap_i2c_dev *dev)
>  {
> -	u16 psc = 0, scll = 0, sclh = 0;
> +	u16 psc = 0, scll = 0, sclh = 0, buf = 0;
>  	u16 fsscll = 0, fssclh = 0, hsscll = 0, hssclh = 0;
>  	unsigned long fclk_rate = 12000000;
>  	unsigned long timeout;
> @@ -287,24 +302,22 @@ static int omap_i2c_init(struct omap_i2c_dev *dev)
>  					   SYSC_AUTOIDLE_MASK);
>  
>  		} else if (dev->rev >= OMAP_I2C_REV_ON_3430) {
> -			u32 v;
> -
> -			v = SYSC_AUTOIDLE_MASK;
> -			v |= SYSC_ENAWAKEUP_MASK;
> -			v |= (SYSC_IDLEMODE_SMART <<
> +			dev->syscstate = SYSC_AUTOIDLE_MASK;
> +			dev->syscstate |= SYSC_ENAWAKEUP_MASK;
> +			dev->syscstate |= (SYSC_IDLEMODE_SMART <<
>  			      __ffs(SYSC_SIDLEMODE_MASK));
> -			v |= (SYSC_CLOCKACTIVITY_FCLK <<
> +			dev->syscstate |= (SYSC_CLOCKACTIVITY_FCLK <<
>  			      __ffs(SYSC_CLOCKACTIVITY_MASK));
>  
> -			omap_i2c_write_reg(dev, OMAP_I2C_SYSC_REG, v);
> +			omap_i2c_write_reg(dev, OMAP_I2C_SYSC_REG,
> +							dev->syscstate);
>  			/*
>  			 * Enabling all wakup sources to stop I2C freezing on
>  			 * WFI instruction.
>  			 * REVISIT: Some wkup sources might not be needed.
>  			 */
> -			omap_i2c_write_reg(dev, OMAP_I2C_WE_REG,
> -							OMAP_I2C_WE_ALL);
> -
> +			dev->westate = OMAP_I2C_WE_ALL;
> +			omap_i2c_write_reg(dev, OMAP_I2C_WE_REG, dev->westate);
>  		}
>  	}
>  	omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, 0);
> @@ -394,23 +407,28 @@ static int omap_i2c_init(struct omap_i2c_dev *dev)
>  	omap_i2c_write_reg(dev, OMAP_I2C_SCLL_REG, scll);
>  	omap_i2c_write_reg(dev, OMAP_I2C_SCLH_REG, sclh);
>  
> -	if (dev->fifo_size)
> -		/* Note: setup required fifo size - 1 */
> -		omap_i2c_write_reg(dev, OMAP_I2C_BUF_REG,
> -					(dev->fifo_size - 1) << 8 | /* RTRSH */
> -					OMAP_I2C_BUF_RXFIF_CLR |
> -					(dev->fifo_size - 1) | /* XTRSH */
> -					OMAP_I2C_BUF_TXFIF_CLR);
> +	if (dev->fifo_size) {
> +		/* Note: setup required fifo size - 1. RTRSH and XTRSH */
> +		buf = (dev->fifo_size - 1) << 8 | OMAP_I2C_BUF_RXFIF_CLR |
> +			(dev->fifo_size - 1) | OMAP_I2C_BUF_TXFIF_CLR;
> +		omap_i2c_write_reg(dev, OMAP_I2C_BUF_REG, buf);
> +	}
>  
>  	/* Take the I2C module out of reset: */
>  	omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, OMAP_I2C_CON_EN);
>  
>  	/* Enable interrupts */
> -	omap_i2c_write_reg(dev, OMAP_I2C_IE_REG,
> -			(OMAP_I2C_IE_XRDY | OMAP_I2C_IE_RRDY |
> +	dev->iestate = (OMAP_I2C_IE_XRDY | OMAP_I2C_IE_RRDY |
>  			OMAP_I2C_IE_ARDY | OMAP_I2C_IE_NACK |
>  			OMAP_I2C_IE_AL)  | ((dev->fifo_size) ?
> -				(OMAP_I2C_IE_RDR | OMAP_I2C_IE_XDR) : 0));
> +				(OMAP_I2C_IE_RDR | OMAP_I2C_IE_XDR) : 0);
> +	omap_i2c_write_reg(dev, OMAP_I2C_IE_REG, dev->iestate);
> +	if (cpu_is_omap34xx()) {
> +		dev->pscstate = psc;
> +		dev->scllstate = scll;
> +		dev->sclhstate = sclh;
> +		dev->bufstate = buf;
> +	}
>  	return 0;
>  }
>  
> -- 
> 1.6.3.3
> 
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-- 
Ben (ben@fluff.org, http://www.fluff.org/)

  'a smiley only costs 4 bytes'