[U-Boot] [PATCH v2] DW SPI: Get clock value from Device Tree

[Jagan Teki]

On Tue, Oct 24, 2017 at 11:38 AM, Marek Vasut <marex at denx.de> wrote:
> On 10/23/2017 01:43 PM, Eugeniy Paltsev wrote:
>> On Thu, 2017-10-19 at 13:20 -0500, Dinh Nguyen wrote:
>>>
>>> On 10/19/2017 10:51 AM, Marek Vasut wrote:
>>>> On 10/19/2017 05:36 PM, Eugeniy Paltsev wrote:
>>>>> On Tue, 2017-10-17 at 20:32 +0530, Jagan Teki wrote:
>>>>>> On Tue, Oct 17, 2017 at 8:27 PM, Alexey Brodkin
>>>>>> <Alexey.Brodkin at synopsys.com> wrote:
>>>>>>> Hi Jagan,
>>>>>>>
>>>>>>>> -----Original Message-----
>>>>>>>> From: Eugeniy Paltsev [mailto:paltsev at synopsys.com]
>>>>>>>> Sent: Tuesday, October 17, 2017 4:33 PM
>>>>>>>> To: jagannadh.teki at gmail.com
>>>>>>>> Cc: u-boot at lists.denx.de; uboot-snps-arc at synopsys.com
>>>>>>>> Subject: [uboot-snps-arc] Re: [PATCH v2] DW SPI: Get clock value from Device Tree
>>>>>>>>>
>>>>>>>>> How hard it is to make others to use clock manager? do you have any list?
>>>>>>>>
>>>>>>>> clock_manager.h is an old (and non-generic) way to deal with different clocks.
>>>>>>>> For example in SOCFPGA_GEN5 and SOCFPGA_ARRIA10 clock_manager.h provides
>>>>>>>> cm_get_spi_controller_clk_hz function to deal with spi controller clock.
>>>>>>>>
>>>>>>>> But today we have another, linux-like alternative: to bind clocks via device tree
>>>>>>>> and manipulate with clocks via generic functions provided by clk.h
>>>>>>>>
>>>>>>>> In this patch I added option to get clock via device tree using standard bindings
>>>>>>>> and restrict clock_manager.h functions usage only to targets which still use it,
>>>>>>>> so new targets can simply bind clock via device tree and they do not need to
>>>>>>>> implement/define something in clock_manager.h
>>>>>>>>
>>>>>>>> So we don't need to make others to use clock manager :)
>>>>>>>
>>>>>>> Maybe it worth trying the other way around and think about switching SOCFPGA platforms to
>>>>>>> generic clk framework?
>>>>>>
>>>>>> Yes, ie what exactly I thought of, thanks!
>>>>>
>>>>> I checked cm_get_spi_controller_clk_hz implementation in SOCFPGA_GEN5 and
>>>>> SOCFPGA_ARRIA10: we can't simply replace it with "fixed-clock" driver as it
>>>>> manipulate with real hardware.
>>>>> The only way to do it is to replace SOCFPGA* clock manager functions by real
>>>>> clock driver.
>>>>>
>>>>> And given I don't have mentioned hardware so I barely can help with
>>>>> those improvements on SOCFPGA. That said if there're no short-term plans to
>>>>> switch SOCFPGA to clk framework maybe we'll be OK with my workaround with #ifdefs?
>>>>
>>>> Wait for Dinh's reply ...
>>>>
>>>
>>> Honestly, I don't have too much time to work on this right now. So I
>>> really don't when it can get done. But it'll go on my to-do list.
>>>
>>> Dinh
>>
>> Yep, thanks for your comments.
>>
>> So, Jagan,
>> given Dinh's reply, could you please apply this patch?
>
> I'd really hate it to start seeing soc-specific ifdefs in drivers,
> that's IMO not acceptable. A __weak override might be a temporary
> solution I'd be willing to live with though.

I would rather like to see some check on clock manager itself whether
CONFIG_IS_ENABLED(CLK) is using or not? this can tends not to use
__weak as well soc #ifdefs in driver.

thanks!
-- 
Jagan Teki
Free Software Engineer | www.openedev.com
U-Boot, Linux | Upstream Maintainer
Hyderabad, India.