Re: Re: [PATCH] powerpc/Kconfig: Make FSL_85XX_CACHE_SRAM configurable

[Scott Wood]

On Tue, 2020-01-21 at 14:38 +0800, çæè wrote:
> åääïScott Wood <oss@xxxxxxxxxxxx>
> åéææï2020-01-21 13:49:59
> æääï"çæè" <wenhu.wang@xxxxxxxx>
> æéäïwangwenhu <wenhu.pku@xxxxxxxxx>,Kumar Gala <galak@xxxxxxxxxxxxxxxxxxx>,B
> enjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>,Paul Mackerras <
> paulus@xxxxxxxxx>,Michael Ellerman <mpe@xxxxxxxxxxxxxx>,
> linuxppc-dev@xxxxxxxxxxxxxxxx,linux-kernel@xxxxxxxxxxxxxxx,
> trivial@xxxxxxxxxx,Rai Harninder <harninder.rai@xxxxxxx>
> äéïRe: [PATCH] powerpc/Kconfig: Make FSL_85XX_CACHE_SRAM configurable>On
> Tue, 2020-01-21 at 13:20 +0800, çæè wrote:
> > > From: Scott Wood <oss@xxxxxxxxxxxx>
> > > Date: 2020-01-21 11:25:25
> > > To:  wangwenhu <wenhu.pku@xxxxxxxxx>,Kumar Gala <
> > > galak@xxxxxxxxxxxxxxxxxxx>,
> > > Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>,Paul Mackerras <
> > > paulus@xxxxxxxxx>,Michael Ellerman <mpe@xxxxxxxxxxxxxx>,
> > > linuxppc-dev@xxxxxxxxxxxxxxxx,linux-kernel@xxxxxxxxxxxxxxx
> > > Cc:  trivial@xxxxxxxxxx,wenhu.wang@xxxxxxxx,Rai Harninder <
> > > harninder.rai@xxxxxxx>
> > > Subject: Re: [PATCH] powerpc/Kconfig: Make FSL_85XX_CACHE_SRAM
> > > configurable>On Mon, 2020-01-20 at 06:43 -0800, wangwenhu wrote:
> > > > > From: wangwenhu <wenhu.wang@xxxxxxxx>
> > > > > 
> > > > > When generating .config file with menuconfig on Freescale BOOKE
> > > > > SOC, FSL_85XX_CACHE_SRAM is not configurable for the lack of
> > > > > description in the Kconfig field, which makes it impossible
> > > > > to support L2Cache-Sram driver. Add a description to make it
> > > > > configurable.
> > > > > 
> > > > > Signed-off-by: wangwenhu <wenhu.wang@xxxxxxxx>
> > > > 
> > > > The intent was that drivers using the SRAM API would select the
> > > > symbol.  What
> > > > is the use case for selecting it manually?
> > > > 
> > > 
> > > With a repository of multiple products(meaning different defconfigs) and
> > > multiple
> > > developers, the Kconfigs of the Kernel Source Tree change frequently. So
> > > the
> > > "make menuconfig"
> > > process is needed for defconfigs' re-generating or updating for the
> > > complexity of dependencies
> > > between different features defined in the Kconfigs.
> > 
> > That doesn't answer my question of how the SRAM code would be useful other
> > than to some other driver that uses the API (which would use
> > "select").  There
> > is no userspace API.  You could use the kernel command line to configure
> > the
> > SRAM but you need to get the address of it for it to be useful.
> > 
> 
> Like you've asked below, via /dev/mem or direct calling within the Kernel.
> And they are not submitted yes, under development.

If they are calling within the kernel, then whatever driver that is should
select FSL_85XX_CACHE_SRAM.  Directly accessing /dev/mem without any way for
the kernel to advertise where it is or which parts of SRAM are available for
use sounds like a bad idea.

-Scott