[PATCH v2] i2c:at91: Add device tree property to set clock-frequency

[Jean-Christophe PLAGNIOL-VILLARD]

I never like that

the  clock-frequency = <400000>; need to be set on each i2c device
and then the i2c subsystem need to choose the slowest

Best Regards,
J.
On Mar 6, 2014, at 9:48 PM, Mark Roszko <mark.roszko at gmail.com> wrote:

> CCing the subsystem maintainer because I left him out on the initial send.
> 
> On Fri, Feb 28, 2014 at 6:05 AM, Ludovic Desroches
> <ludovic.desroches at atmel.com> wrote:
>> On Mon, Feb 24, 2014 at 08:50:45PM -0500, Marek Roszko wrote:
>>> This adds the ability to set "clock-frequency" in the device tree for the i2c bus 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>
>> 
>> Acked-by: Ludovic Desroches <ludovic.desroches at atmel.com>
>> 
>> Thanks
>> 
>>> ---
>>> 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>;
>>> 
>>>      24c512 at 50 {
>>>              compatible = "24c512";
>>> diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
>>> index 843d012..a407050 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;
>>> +     int 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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> 
> 
> 
> -- 
> Mark
> 
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