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

[Eugeniy Paltsev]

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?

-- 
 Eugeniy Paltsev