Re: [PATCH 2/2] i2c-ocore: support 16 and 32-bit wide registers

[Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]

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On Tue, May 08, 2012 at 06:55:29PM +0530, Jayachandran C wrote:
> From: Ganesan Ramalingam <ganesanr-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
> 
> Some architectures supports only 16-bit or 32-bit read/write access
> to their iospace. Add a 'regwidth' platform and OF parameter which
> specifies the IO width to support these platforms.
> 
> regwidth can be specified as 1, 2 or 4, and has a default value
> of 1 if it is unspecified.
> 
> Signed-off-by: Ganesan Ramalingam <ganesanr-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
> Signed-off-by: Jayachandran C <jayachandranc-oSioyQM9ZPnuBjGU1YDckgC/G2K4zDHf@public.gmane.org>

Hmm, this is a generic issue and should not be handled with a driver
specific property. CCing devicetree-discuss, maybe there is already a
way to handle this? The already existing 'regstep' looks suspicious, too?
Can't find any documentation for it.

Thanks,

   Wolfram

> ---
>  drivers/i2c/busses/i2c-ocores.c |   32 ++++++++++++++++++++++++++++++--
>  include/linux/i2c-ocores.h      |    1 +
>  2 files changed, 31 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-ocores.c
> index ebd2700..1313145 100644
> --- a/drivers/i2c/busses/i2c-ocores.c
> +++ b/drivers/i2c/busses/i2c-ocores.c
> @@ -19,6 +19,9 @@
>   * - regstep         : size of device registers in bytes
>   * - clock-frequency : frequency of bus clock in Hz
>   * 
> + * Optional properties:
> + * - regwidth        : io register width in bytes (1, 2 or 4)
> +
>   * Example:
>   *
>   *  i2c0: ocores@a0000000 {
> @@ -27,6 +30,7 @@
>   *              interrupts = <10>;
>   *
>   *              regstep = <1>;
> + *              regwidth = <1>;
>   *              clock-frequency = <20000000>;
>   *
>   * -- Devices connected on this I2C bus get
> @@ -60,6 +64,7 @@
>  struct ocores_i2c {
>  	void __iomem *base;
>  	int regstep;
> +	int regwidth;
>  	wait_queue_head_t wait;
>  	struct i2c_adapter adap;
>  	struct i2c_msg *msg;
> @@ -102,12 +107,22 @@ struct ocores_i2c {
>  
>  static inline void oc_setreg(struct ocores_i2c *i2c, int reg, u8 value)
>  {
> -	iowrite8(value, i2c->base + reg * i2c->regstep);
> +	if (i2c->regwidth == 4)
> +		iowrite32(value, i2c->base + reg * i2c->regstep);
> +	else if (i2c->regwidth == 2)
> +		iowrite16(value, i2c->base + reg * i2c->regstep);
> +	else
> +		iowrite8(value, i2c->base + reg * i2c->regstep);
>  }
>  
>  static inline u8 oc_getreg(struct ocores_i2c *i2c, int reg)
>  {
> -	return ioread8(i2c->base + reg * i2c->regstep);
> +	if (i2c->regwidth == 4)
> +		return ioread32(i2c->base + reg * i2c->regstep);
> +	else if (i2c->regwidth == 2)
> +		return ioread16(i2c->base + reg * i2c->regstep);
> +	else
> +		return ioread8(i2c->base + reg * i2c->regstep);
>  }
>  
>  static void ocores_process(struct ocores_i2c *i2c)
> @@ -267,6 +282,10 @@ static int ocores_i2c_of_probe(struct platform_device* pdev,
>  	}
>  	i2c->clock_khz = be32_to_cpup(val) / 1000;
>  
> +	val = of_get_property(pdev->dev.of_node, "regwidth", NULL);
> +	if (val)
> +		i2c->regwidth = be32_to_cpup(val);
> +
>  	return 0;
>  }
>  #else
> @@ -309,12 +328,21 @@ static int __devinit ocores_i2c_probe(struct platform_device *pdev)
>  	pdata = pdev->dev.platform_data;
>  	if (pdata) {
>  		i2c->regstep = pdata->regstep;
> +		i2c->regwidth = pdata->regwidth;
>  		i2c->clock_khz = pdata->clock_khz;
>  	} else {
>  		ret = ocores_i2c_of_probe(pdev, i2c);
>  		if (ret)
>  			return ret;
>  	}
> +	if (i2c->regwidth == 0)
> +		i2c->regwidth = 1;	/* not configured, use default */
> +	else if (i2c->regwidth != 1 && i2c->regwidth != 2 &&
> +			i2c->regwidth != 4) {
> +		dev_err(&pdev->dev, "Invalid register width %d\n",
> +			i2c->regwidth);
> +		return -EINVAL;
> +	}
>  
>  	ocores_init(i2c);
>  
> diff --git a/include/linux/i2c-ocores.h b/include/linux/i2c-ocores.h
> index 4d5e57f..d1258ad 100644
> --- a/include/linux/i2c-ocores.h
> +++ b/include/linux/i2c-ocores.h
> @@ -13,6 +13,7 @@
>  
>  struct ocores_i2c_platform_data {
>  	u32 regstep;   /* distance between registers */
> +	u32 regwidth;  /* io read/write register witdth */
>  	u32 clock_khz; /* input clock in kHz */
>  	u8 num_devices; /* number of devices in the devices list */
>  	struct i2c_board_info const *devices; /* devices connected to the bus */
> -- 
> 1.7.9.5
> 
> 
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-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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