Re: [PATCH] Revert "mtd: rawnand: denali: get ->setup_data_interface() working again"

[Marek Vasut <marex@xxxxxxx>]

On 2/12/20 10:00 AM, Masahiro Yamada wrote:
> Hi Marek,

Hi,

> On Wed, Feb 12, 2020 at 5:35 AM Marek Vasut <marex@xxxxxxx> wrote:
>>
>> On 2/11/20 5:07 PM, Miquel Raynal wrote:
>>> Hi Marek, Masahiro,
>>>
>>> Marek Vasut <marex@xxxxxxx> wrote on Tue, 11 Feb 2020 11:04:10 +0100:
>>>
>>>> On 2/5/20 11:08 AM, Marek Vasut wrote:
>>>>> On 2/5/20 10:50 AM, Miquel Raynal wrote:
>>>>>> Hi Marek,
>>>>>>
>>>>>> Marek Vasut <marex@xxxxxxx> wrote on Wed, 5 Feb 2020 10:41:05 +0100:
>>>>>>
>>>>>>> On 2/5/20 10:12 AM, Miquel Raynal wrote:
>>>>>>>> Hi Marek,
>>>>>>>>
>>>>>>>> Marek Vasut <marex@xxxxxxx> wrote on Wed,  5 Feb 2020 08:08:34 +0100:
>>>>>>>>
>>>>>>>>> This reverts commit d311e0c27b8fcc27f707f8cac48cd8bdc4155224, which
>>>>>>>>> completely breaks NAND access on Altera SoCFPGA (detected on ArriaV
>>>>>>>>> SoC).
>>>>>>>>>
>>>>>>>>> On SoCFPGA, denali->clk_rate = 31.25 MHz and denali->clk_x_rate = 125 MHz,
>>>>>>>>> hence the driver sets NAND_KEEP_TIMINGS flag.
> 
> 
> Interesting.
> I have never seen such clock rates before.
> 
> 
> For all known upstream platforms
> (Altera SOCFPGA, Socionext UniPhier, Intel MRST),
> the NAND controller core clock is 50 MHz,
> the NAND bus clock is 200MHz.

You can configure whatever rate you want in the QSys HPS component.

> What would happen if you hard-code:
> denali->clk_rate = 50000000;
> denali->clk_x_rate = 200000000;

It will not work, because the IP would be using incorrect clock.

> like I had already suggested to Tim Sander:
> https://lore.kernel.org/lkml/CAK7LNAQOCoJC0RzOhTEofHdR+zU5sQTxV-t4nERBExW1ddW5hw@xxxxxxxxxxxxxx/
> 
> Unfortunately, he did not want to do it, but
> I am still interested in this experiment because
> I suspect this might be a bug of drivers/clk/socfpga/.

No, this is a feature of the platform, you can configure any clock you
want pretty much.

> 4.19.10 kernel (, which Tim Sander agreed the timing was working fine)
> was hard-coding them in order to deal with the immature SOCFPGA clock driver.

The 4.19 was working fine for Tim (and me as well), because it didn't
have this bug which this patch removes.

[...]

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