Re: [PATCH 1/2 V2] MXS: Set I2C timing registers for mxs-i2c

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

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Hi Marek,

thanks for the submission.

On Fri, Jul 06, 2012 at 08:09:15AM +0200, Marek Vasut wrote:
> This patch configures the I2C bus timing registers according
> to information passed via DT. Currently, 100kHz and 400kHz
> modes are supported.

That limitation should be mentioned in the documentation.

> 
> The TIMING2 register value is wrong in the documentation for
> i.MX28! This was found and fixed by:
>   Shawn Guo <shawn.guo-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> 
> Signed-off-by: Marek Vasut <marex-ynQEQJNshbs@public.gmane.org>
> Cc: Detlev Zundel <dzu-ynQEQJNshbs@public.gmane.org>
> CC: Dong Aisheng <b29396-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
> CC: Fabio Estevam <fabio.estevam-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
> Cc: Linux ARM kernel <linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>
> Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> CC: Sascha Hauer <s.hauer-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
> CC: Shawn Guo <shawn.guo-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> Cc: Stefano Babic <sbabic-ynQEQJNshbs@public.gmane.org>
> CC: Uwe Kleine-König <u.kleine-koenig-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
> Cc: Wolfgang Denk <wd-ynQEQJNshbs@public.gmane.org>
> Cc: Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
> ---
>  Documentation/devicetree/bindings/i2c/i2c-mxs.txt |    2 +
>  arch/arm/boot/dts/imx28.dtsi                      |    2 +
>  drivers/i2c/busses/i2c-mxs.c                      |   56 +++++++++++++++++++++
>  3 files changed, 60 insertions(+)
> 
> V2: (even though technically V<around 4>, I really need to start doing this
>      patch management properly, it's quite a mess now)

Yup, it was :) Thanks for resending.

>     Fixed static const struct mxs_i2c_speed_config ... pointed by Dong.
> 
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-mxs.txt b/Documentation/devicetree/bindings/i2c/i2c-mxs.txt
> index 1bfc02d..2ed5332 100644
> --- a/Documentation/devicetree/bindings/i2c/i2c-mxs.txt
> +++ b/Documentation/devicetree/bindings/i2c/i2c-mxs.txt
> @@ -4,6 +4,7 @@ Required properties:
>  - compatible: Should be "fsl,<chip>-i2c"
>  - reg: Should contain registers location and length
>  - interrupts: Should contain ERROR and DMA interrupts
> +- clock-frequency: desired I2C bus clock frequency in Hz.
>  
>  Examples:
>  
> @@ -13,4 +14,5 @@ i2c0: i2c@80058000 {
>  	compatible = "fsl,imx28-i2c";
>  	reg = <0x80058000 2000>;
>  	interrupts = <111 68>;
> +	clock-frequency = <400000>;
>  };
> diff --git a/arch/arm/boot/dts/imx28.dtsi b/arch/arm/boot/dts/imx28.dtsi
> index ee3778a..832d30a 100644
> --- a/arch/arm/boot/dts/imx28.dtsi
> +++ b/arch/arm/boot/dts/imx28.dtsi
> @@ -419,6 +419,7 @@
>  				compatible = "fsl,imx28-i2c";
>  				reg = <0x80058000 2000>;
>  				interrupts = <111 68>;
> +				clock-frequency = <400000>;
>  				status = "disabled";
>  			};
>  
> @@ -428,6 +429,7 @@
>  				compatible = "fsl,imx28-i2c";
>  				reg = <0x8005a000 2000>;
>  				interrupts = <110 69>;
> +				clock-frequency = <400000>;

NACK on that. Not all slaves can do 400KHz, so this is not a sensible
default.

>  				status = "disabled";
>  			};
>  
> diff --git a/drivers/i2c/busses/i2c-mxs.c b/drivers/i2c/busses/i2c-mxs.c
> index 04eb441..47a7e20 100644
> --- a/drivers/i2c/busses/i2c-mxs.c
> +++ b/drivers/i2c/busses/i2c-mxs.c
> @@ -46,6 +46,10 @@
>  #define MXS_I2C_CTRL0_DIRECTION			0x00010000
>  #define MXS_I2C_CTRL0_XFER_COUNT(v)		((v) & 0x0000FFFF)
>  
> +#define MXS_I2C_TIMING0		(0x10)
> +#define MXS_I2C_TIMING1		(0x20)
> +#define MXS_I2C_TIMING2		(0x30)
> +
>  #define MXS_I2C_CTRL1		(0x40)
>  #define MXS_I2C_CTRL1_SET	(0x44)
>  #define MXS_I2C_CTRL1_CLR	(0x48)
> @@ -97,6 +101,25 @@
>  #define MXS_CMD_I2C_READ	(MXS_I2C_CTRL0_SEND_NAK_ON_LAST | \
>  				 MXS_I2C_CTRL0_MASTER_MODE)
>  
> +struct mxs_i2c_speed_config {
> +	uint32_t	timing0;
> +	uint32_t	timing1;
> +	uint32_t	timing2;
> +};
> +
> +/* Timing values for the default 24MHz clock supplied into the i2c block. */
> +static const struct mxs_i2c_speed_config mxs_i2c_95kHz_config = {

Hmm, the 100KHz vs 95KHz issue is confusing. My suggestion would be to
name this mxs_i2c_100kHz_config and write a comment that this is
technically 95Khz due to limitation of the docs (or whatever). If you
want to keep the name, then a similar comment should be placed...


> +	.timing0	= 0x00780030,
> +	.timing1	= 0x00800030,
> +	.timing2	= 0x00300030,
> +};
> +
> +static const struct mxs_i2c_speed_config mxs_i2c_400kHz_config = {
> +	.timing0	= 0x000f0007,
> +	.timing1	= 0x001f000f,
> +	.timing2	= 0x00300030,
> +};
> +
>  /**
>   * struct mxs_i2c_dev - per device, private MXS-I2C data
>   *
> @@ -112,11 +135,17 @@ struct mxs_i2c_dev {
>  	struct completion cmd_complete;
>  	u32 cmd_err;
>  	struct i2c_adapter adapter;
> +	const struct mxs_i2c_speed_config *speed;
>  };
>  
>  static void mxs_i2c_reset(struct mxs_i2c_dev *i2c)
>  {
>  	stmp_reset_block(i2c->regs);
> +
> +	writel(i2c->speed->timing0, i2c->regs + MXS_I2C_TIMING0);
> +	writel(i2c->speed->timing1, i2c->regs + MXS_I2C_TIMING1);
> +	writel(i2c->speed->timing2, i2c->regs + MXS_I2C_TIMING2);
> +
>  	writel(MXS_I2C_IRQ_MASK << 8, i2c->regs + MXS_I2C_CTRL1_SET);
>  	writel(MXS_I2C_QUEUECTRL_PIO_QUEUE_MODE,
>  			i2c->regs + MXS_I2C_QUEUECTRL_SET);
> @@ -319,6 +348,28 @@ static const struct i2c_algorithm mxs_i2c_algo = {
>  	.functionality = mxs_i2c_func,
>  };
>  
> +static int mxs_i2c_get_ofdata(struct mxs_i2c_dev *i2c)
> +{
> +	uint32_t speed;
> +	struct device *dev = i2c->dev;
> +	struct device_node *node = dev->of_node;
> +	int ret;
> +
> +	if (!node)
> +		return -EINVAL;
> +
> +	i2c->speed = &mxs_i2c_95kHz_config;

...here

> +	ret = of_property_read_u32(node, "clock-frequency", &speed);
> +	if (ret)
> +		dev_warn(dev, "No I2C speed selected, using 100kHz\n");
> +	else if (speed == 400000)
> +		i2c->speed = &mxs_i2c_400kHz_config;
> +	else if (speed != 100000)
> +		dev_warn(dev, "Invalid I2C speed selected, using 100kHz\n");

Minor: s/Invalid/Unsupported/ ?

> +
> +	return 0;
> +}
> +
>  static int __devinit mxs_i2c_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
> @@ -358,6 +409,11 @@ static int __devinit mxs_i2c_probe(struct platform_device *pdev)
>  		return err;
>  
>  	i2c->dev = dev;
> +
> +	err = mxs_i2c_get_ofdata(i2c);
> +	if (err)
> +		return err;
> +
>  	platform_set_drvdata(pdev, i2c);
>  
>  	/* Do reset to enforce correct startup after pinmuxing */
> -- 
> 1.7.10
> 

Regards,

   Wolfram

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Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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