[PATCH v3] i2c:at91: Add device tree property to set clock-frequency

[Jean-Christophe PLAGNIOL-VILLARD]

On Mar 11, 2014, at 12:25 PM, Marek Roszko <mark.roszko at gmail.com> wrote:

> This adds the ability to set "clock-frequency" in the device tree for the at91
> i2cbus following the naming of other i2c bus implementations. If the property
> is not set,the clock frequency will default to the previously used define 
> of 100KHz.
> 
> Signed-off-by: Marek Roszko <mark.roszko at gmail.com>
> ---
> v3:		
> 		-changed bus_clk_rate to u32
> v2:
>        -fixed return code usage and check to not compare agaisnt less than zero
> 
> ---
> Documentation/devicetree/bindings/i2c/i2c-at91.txt |    2 ++
> drivers/i2c/busses/i2c-at91.c                      |   10 ++++++++--
> 2 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-at91.txt b/Documentation/devicetree/bindings/i2c/i2c-at91.txt
> index 4fade84..388f0a2 100644
> --- a/Documentation/devicetree/bindings/i2c/i2c-at91.txt
> +++ b/Documentation/devicetree/bindings/i2c/i2c-at91.txt
> @@ -12,6 +12,7 @@ Required properties :
> - clocks: phandles to input clocks.
> 
> Optional properties:
> +- clock-frequency: Desired I2C bus frequency in Hz, otherwise defaults to 100000
> - Child nodes conforming to i2c bus binding
> 
> Examples :
> @@ -23,6 +24,7 @@ i2c0: i2c at fff84000 {
> 	#address-cells = <1>;
> 	#size-cells = <0>;
> 	clocks = <&twi0_clk>;
> +	clock-frequency = <400000>;
> 
The bindings is wrong it’s not the bus frequency but the max frequency

as you describe the bus not the device frequency. And this is this one that limit the bus

Best Regards,
J.
> 	24c512 at 50 {
> 		compatible = "24c512";
> diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
> index 843d012..334c851 100644
> --- a/drivers/i2c/busses/i2c-at91.c
> +++ b/drivers/i2c/busses/i2c-at91.c
> @@ -32,7 +32,7 @@
> #include <linux/slab.h>
> #include <linux/platform_data/dma-atmel.h>
> 
> -#define TWI_CLK_HZ		100000			/* max 400 Kbits/s */
> +#define DEFAULT_TWI_CLK_HZ		100000		/* max 400 Kbits/s */
> #define AT91_I2C_TIMEOUT	msecs_to_jiffies(100)	/* transfer timeout */
> #define AT91_I2C_DMA_THRESHOLD	8			/* enable DMA if transfer size is bigger than this threshold */
> 
> @@ -711,6 +711,7 @@ static int at91_twi_probe(struct platform_device *pdev)
> 	struct resource *mem;
> 	int rc;
> 	u32 phy_addr;
> +	u32 bus_clk_rate;
> 
> 	dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
> 	if (!dev)
> @@ -756,7 +757,12 @@ static int at91_twi_probe(struct platform_device *pdev)
> 			dev->use_dma = true;
> 	}
> 
> -	at91_calc_twi_clock(dev, TWI_CLK_HZ);
> +	rc = of_property_read_u32(dev->dev->of_node, "clock-frequency",
> +			&bus_clk_rate);
> +	if (rc)
> +		bus_clk_rate = DEFAULT_TWI_CLK_HZ;
> +
> +	at91_calc_twi_clock(dev, bus_clk_rate);
> 	at91_init_twi_bus(dev);
> 
> 	snprintf(dev->adapter.name, sizeof(dev->adapter.name), "AT91");
> -- 
> 1.7.10.4
> 
> 
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