[U-Boot] [PATCH V4] I2C: mxc_i2c rework

[Jason Hui]

Hi, Marek,

On Sat, Jul 30, 2011 at 1:09 AM, Marek Vasut <marek.vasut at gmail.com> wrote:
> On Friday, July 29, 2011 01:24:49 PM Jason Hui wrote:
>> Hi, Marek,
>>
>> On Fri, Jul 29, 2011 at 5:32 PM, Marek Vasut <marek.vasut at gmail.com> wrote:
>> > Rewrite the mxc_i2c driver.
>> >  * This version is much closer to Linux implementation.
>> >  * Fixes IPG_PERCLK being incorrectly used as clock source
>> >  * Fixes behaviour of the driver on iMX51
>> >  * Clean up coding style a bit ;-)
>>
>> I don't think you did the right thing by chaning IPG_PERCLK to IPG_CLK
>> As I said, the IPG_CLK is for IP register clock, while IPG_PERCLK is for
>> i2c function clock.
>>
>> if you run clock command from mx51evk, you will get:
>> ...
>> ipg clock     : 66500000Hz
>> ipg per clock : 665000000Hz
>> MX51EVK U-Boot >
>>
>> It will give you that ipg per clock is 665M, which seems too big. It
>> is due to we configure
>> the pre-divider/pos-devider for perclk to zero, which leads to ipg_per
>> clock to be same as pll2 clock.
>> But I don't think this will have some issue.
>
> Yes it will, the divider will be computed to be maximum in all cases ... you
> won't be able it divide 665MHz by anything from the table 40-7 in MX51RM to
> achieve any reasonable frequency.
>
> On the contrary, 66.5MHz does give fine results.

it that, we can change the ipg_perclk to low freq, but we should not change the
i2c clock to ipg_clk, this is not correct.

>
>>
>> BTW, I have applied your patch and test on mx53evk board, it seems the
>> i2c does not work correctly.
>
> Great. The clock used by the I2C module for this task are likely the
> module_clock, which are -- like on MX51 -- 66.5MHz. What do you get when you run
> the "clock" command on MX53EVK ?

I'm not in the office for the whole next week, thus, I can't give you
the clock output for
mx53evk, but I'm sure the ipg_perclk on mx53evk is not set at 66.5Mhz.

Jason

>
> Thanks
>
>> After apply your patch:
>> MX53EVK U-Boot > pmic dump  30
>> PMIC ID: 0x0000ffff [Rev: unknown]
>>
>> 0x00: 0001ffff 00ffffff 0039ffff 0000ffff 00ffffff 0000ffff 0000ffff
>> 0000ffff 0x08: 0000ffff 0000ffff 0000ffff 0000ffff 0000ffff 0000ffff
>> 0000ffff 0040ffff 0x10: 0000ffff 0000ffff 0000ffff 0000ffff 0000ffff
>> 0001ffff 0000ffff 0000ffff 0x18: 0045ffff 0045ffff 0000ffff 0080ffff
>> 0021ffff 0000ffff 0002ffff 0000ffff 0x20: 0004ffff 0000ffff 0021ffff
>> 0000ffff 0000ffff 0000ffff 0000ffff 0000ffff 0x28: 0000ffff 0000ffff
>> 0000ffff 0000ffff 0000ffff 0004ffff 0000ffff 00aeffff
>>
>> The old:
>> MX53EVK U-Boot > pmic dump 30
>> PMIC ID: 0x000045d0 [Rev: 2.0]
>>
>> 0x00: 00015088 00ffffff 00395208 00000081 00fff7ff 0000401c 00000418
>> 000045d0 0x08: 00000000 00000000 00000001 00000000 00000000 00000040
>> 00000000 00400000 0x10: 00000000 00000000 00000000 00000000 00000011
>> 0001ffff 00000000 00007fff 0x18: 00454a52 00456739 0000631a 0080739c
>> 0021284a 00000a0a 00024fd0 000001d8 0x20: 00049208 00000000 00218000
>> 00000000 00000000 00000000 00000000 00000000 0x28: 00000000 00000000
>> 00000000 00008000 00000000 00046046 000001c0 00aeeaee
>>
>> Jason
>