Re: [PATCH v2 14/18] serial: intel: Add CCF support

[Wu, Songjun]

On 8/6/2018 3:20 PM, Geert Uytterhoeven wrote:
> Hi Songjun,
>
> On Mon, Aug 6, 2018 at 9:15 AM Wu, Songjun <songjun.wu@xxxxxxxxxxxxxxx> wrote:
> > On 8/5/2018 5:03 AM, Arnd Bergmann wrote:
> > > On Sat, Aug 4, 2018 at 2:43 PM, Greg Kroah-Hartman
> > > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> > > > On Sat, Aug 04, 2018 at 12:54:22PM +0200, Hauke Mehrtens wrote:
> > > > > On 08/03/2018 12:30 PM, Greg Kroah-Hartman wrote:
> > > > > > On Fri, Aug 03, 2018 at 03:33:38PM +0800, Wu, Songjun wrote:
> > > > > This patch makes it possible to use it with the legacy lantiq code and
> > > > > also with the common clock framework. I see multiple options to fix this
> > > > > problem.
> > > > >
> > > > > 1. The current approach to have it as a compile variant for a) legacy
> > > > > lantiq arch code without common clock framework and b) support for SoCs
> > > > > using the common clock framework.
> > > > > 2. Convert the lantiq arch code to the common clock framework. This
> > > > > would be a good approach, but it need some efforts.
> > > > > 3. Remove the arch/mips/lantiq code. There are still users of this code.
> > > > > 4. Use the old APIs also for the new xRX500 SoC, I do not like this
> > > > > approach.
> > > > > 5. Move lantiq_soc.h to somewhere in include/linux/ so it is globally
> > > > > available and provide some better wrapper code.
> > > > I don't really care what you do at this point in time, but you all
> > > > should know better than the crazy #ifdef is not allowed to try to
> > > > prevent/allow the inclusion of a .h file.  Checkpatch might have even
> > > > warned you about it, right?
> > > >
> > > > So do it correctly, odds are #5 is correct, as that makes it work like
> > > > any other device in the kernel.  You are not unique here.
> > > The best approach here would clearly be 2. We don't want platform
> > > specific header files for doing things that should be completely generic.
> > >
> > > Converting lantiq to the common-clk framework obviously requires
> > > some work, but then again the whole arch/mips/lantiq/clk.c file
> > > is fairly short and maybe not that hard to convert.
> > >
> > > >From looking at arch/mips/lantiq/xway/sysctrl.c, it appears that you
> > > already use the clkdev lookup mechanism for some devices without
> > > using COMMON_CLK, so I would assume that you can also use those
> > > for the remaining clks, which would be much simpler. It registers
> > > one anonymous clk there as
> > >
> > >           clkdev_add_pmu("1e100c00.serial", NULL, 0, 0, PMU_ASC1);
> > >
> > > so why not add replace that with two named clocks and just use
> > > the same names in the DT for the newer chip?
> > >
> > >         Arnd
> > We discussed internally and have another solution for this issue.
> > Add one lantiq.h in the serial folder, and use "#ifdef preprocessor" in
> > lantiq.h,
> > also providing no-op stub functions in the #else case, then call those
> > functions
> > unconditionally from lantiq.c to avoid #ifdef in C file.
> >
> > To support CCF in legacy product is another topic, is not included in
> > this patch.
> >
> > The implementation is as followingï
> > #ifdef CONFIG_LANTIQ
> > #include <lantiq_soc.h>
> > #else
> > #define LTQ_EARLY_ASC 0
> > #define CPHYSADDR(_val) 0
> >
> > static inline struct clk *clk_get_fpi(void)
> > {
> >       return NULL;
> > }
> > #endif
> Why not use clkdev_add(), as Arnd suggested?
> That would be a 3-line patch without introducing a new header file and an ugly
> #ifdef, which complicates compile coverage testing?
>
> Gr{oetje,eeting}s,
>
>                          Geert
The reason we add a new head file is also for two macros(LTQ_EARLY_ASC 
and CPHYSADDR)
used by legacy product. We need to provide the no-op stub for these two 
macro for new product.