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

[Wu, Songjun]

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)
{
ÂÂÂ return NULL;
}
#endif