Re: [PATCH] powerpc: i2c-mpc: make speed registers configurable via FDT

["Grant Likely" <grant.likely@secretlab.ca>]

On Thu, Jul 31, 2008 at 11:22 AM, Wolfgang Grandegger <wg@grandegger.com> wrote:
> Jon Smirl wrote:
>>
>> On 7/31/08, Wolfgang Grandegger <wg@grandegger.com> wrote:
>>>
>>> Grant Likely wrote:
>>>
>>>> On Fri, Jul 25, 2008 at 11:19:41AM -0500, Timur Tabi wrote:
>>>>
>>>>> Wolfgang Grandegger wrote:
>>>>>
>>>>>
>>>>>> I know but we still need an algorithm for MPC52xx and MPC82xx as well.
>>>>>>
>>>>> That's true, but I still think hard-coding values of DFSR and FDR in
>>>>> the
>>>
>>> device
>>>>>
>>>>> tree is not a good way to do this.
>>>>>
>>>> I agree, it should encode real frequencies, not raw register values.
>>>>
>>>  Digging deeper I'm frightened by plenty of platform specific code. We
>>> would
>>> need:
>>>
>>>  - one table of divider,fdr,dfsr values for the MPC82/3/5/6xx processors
>>>  (already available from Timur's U-Boot implementation)
>>>
>>>  - one table of divider,fdr values for the MPC5200 rev A.
>>>
>>>  - one table of divider,fdr values for the MPC5200 rev B.
>>>  (the Rev. B has two more pre-scaler bits).
>>
>> Aren't the tables in the manual there just to make it easy for a human
>> to pick out the line they want? For a computer you'd program the
>> formula that was used to create the tables.
>
> I have the formulas to create the tables, also for the MPC5200 Rev. A and B.

Oh, hey, even better.

> That was not my point. I'm worried about arch specific code in i2c-mpc.c. It
> should go somewhere to arch/powerpc.

i2c-mpc *is* arch specific.  I really don't think you need to worry
about adding a block of code for each supported SoC family.  Just
change the of_match table to look something like this:

static const struct of_device_id mpc_i2c_of_match[] = {
	{.compatible = "fsl,mpc5200b-i2c", .data = fsl_i2c_mpc5200b_set_freq, },
	{.compatible = "fsl,mpc5200-i2c", .data = fsl_i2c_mpc5200_set_freq, },
	{.compatible = "fsl,mpc8260-i2c", .data = fsl_i2c_mpc8xxx_set_freq, },
	{.compatible = "fsl,mpc8349-i2c", .data = fsl_i2c_mpc8xxx_set_freq, },
	{.compatible = "fsl,mpc8540-i2c", .data = fsl_i2c_mpc8xxx_set_freq, },
	{.compatible = "fsl,mpc8543-i2c", .data = fsl_i2c_mpc8xxx_div2_set_freq, },
	{.compatible = "fsl,mpc8544-i2c", .data = fsl_i2c_mpc8xxx_div3_set_freq, },

        /* keep this only for older device trees with some support
code to figure out
           what .data should have pointed to. */
	{.compatible = "fsl-i2c", },
	{},
};
MODULE_DEVICE_TABLE(of, mpc_i2c_of_match);

g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.