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

[Jagan Teki]

On Mon, Oct 30, 2017 at 5:12 PM, Marek Vasut <marex at denx.de> wrote:
> On 10/30/2017 12:36 PM, Jagan Teki wrote:
>> On Mon, Oct 30, 2017 at 4:24 PM, Marek Vasut <marex at denx.de> wrote:
>>> On 10/30/2017 07:04 AM, Jagan Teki wrote:
>>>> On Sat, Oct 28, 2017 at 5:09 PM, Marek Vasut <marex at denx.de> wrote:
>>>>> On 10/27/2017 03:54 PM, Eugeniy Paltsev wrote:
>>>>>> On Tue, 2017-10-24 at 15:22 +0530, Jagan Teki wrote:
>>>>>>> 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.
>>>>>>>
>>>>>>
>>>>>> Actually I don't understand what do you mean.
>>>>>> Even if I add any #ifdefs to the clock_manager.h I still need to wrap clock_manager.h
>>>>>> include with #ifdefs as clock_manager.h is defined only for two
>>>>>> targets - SOCFPGA_GEN5 and SOCFPGA_ARRIA10.
>>>>>>
>>>>>> #if defined(CONFIG_TARGET_SOCFPGA_GEN5) || defined(CONFIG_TARGET_SOCFPGA_ARRIA10)
>>>>>> #include <asm/arch/clock_manager.h>
>>>>>> #endif
>>>>>>
>>>>>> And I think it is better to add this #ifdef in driver than create empty
>>>>>> clock_manager.h file for every new target which uses this driver.
>>>>
>>>> Check CLK in clock-manager like below, of-course cm_get_l4_noc_hz used
>>>> in other IP's as well. we need to carefully adding these check and if
>>>> require add CLK for remaining drivers as well. the reason for adding
>>>> checks in clock-manager is it may be removable code if all use CLK.
>>>
>>> I do not understand what you're trying to tell me, but the patch below
>>> makes no sense. What I would like to see is a weak function in the
>>> driver and that function be overriden in the socfpga clock manager.
>>
>> I'm trying to avoid __weak or #ifdef on driver instead make changes in
>> clock manager which will remove in future(once all moved with CLK)
>
> Well, if you do the proposed change, socfpga will break. The __weak is
> the least possible evil here and I can live with that for now.

Yes, __weak can be possible evil here but since I'm planning to apply
this in next version, I'm hoping possible change that shouldn't effect
the driver. I see some __weak's last from many releases that doesn't
resolve properly and they are still __weak functions only.

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