Gah, what a thread...
On Fri, Jun 15, 2012 at 3:18 PM, Lee Jones <lee.jones@xxxxxxxxxx> wrote:
> On 15/06/12 14:05, Srinidhi Kasagar wrote:
>> On Fri, Jun 15, 2012 at 14:45:11 +0200, Lee Jones wrote:
>>> On 15/06/12 12:50, Srinidhi Kasagar wrote:
>>>>> +static struct nmk_i2c_controller u8500_i2c = {
>>>>> + /*
>>>>> + * Slave data setup time; 250ns, 100ns, and 10ns, which
>>>>> + * is 14, 6 and 2 respectively for a 48Mhz i2c clock.
>>>>> + */
>>>>> + .slsu = 0xe,
>>>>> + .tft = 1, /* Tx FIFO threshold */
>>>>> + .rft = 8, /* Rx FIFO threshold */
>>>>> + .clk_freq = 100000, /* std. mode operation */
>>>>> + .timeout = 200, /* Slave response timeout(ms) */
>>>>> + .sm = I2C_FREQ_MODE_FAST,
>>>>
>>>> How is this possible? you are setting clk_freq as 100kb/s and mode
>>>> as fast mode which is supposed to be 400kb/s.
>>>
>>> That's not how I read it:
>>
>>
>> But it is not readable. It confuses people.
>
> I understood it. :)
>
> If you think it's unclear speak to the author, Linus. He's CC'ed.
Author of what? The i2c driver was written by Srinidhi. (The
MODULE_AUTHOR() clause should be a good hint...)
But it's true that board data for the ux500 kernel use
100000 Hz and I2C_FREQ_MODE_FAST, in the board-mop500.c
file, like this:
U8500_I2C_CONTROLLER(0, 0xe, 1, 8, 100000, 200, I2C_FREQ_MODE_FAST);
U8500_I2C_CONTROLLER(1, 0xe, 1, 8, 100000, 200, I2C_FREQ_MODE_FAST);
U8500_I2C_CONTROLLER(2, 0xe, 1, 8, 100000, 200, I2C_FREQ_MODE_FAST);
U8500_I2C_CONTROLLER(3, 0xe, 1, 8, 100000, 200, I2C_FREQ_MODE_FAST);
This is indeed a bit odd. But obviously it works... But reading some
fixes in another tree it seems it should look like this:
/*
* The board uses 4 i2c controllers, initialize all of
* them with slave data setup time of 250 ns,
* Tx & Rx FIFO threshold values as 1 and standard
* mode of operation
*/
U8500_I2C_CONTROLLER(0, 0xe, 1, 8, 400000, 200, I2C_FREQ_MODE_FAST);
U8500_I2C_CONTROLLER(1, 0xe, 1, 8, 400000, 200, I2C_FREQ_MODE_FAST);
U8500_I2C_CONTROLLER(2, 0xe, 1, 8, 400000, 200, I2C_FREQ_MODE_FAST);
U8500_I2C_CONTROLLER(3, 0xe, 1, 8, 400000, 200, I2C_FREQ_MODE_FAST);
Which makes *much* more sense.
I'll cook a separate patch for this or something.
Thanks,
Linus Walleij
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