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

[çæè]

åääïScott Wood <oss@xxxxxxxxxxxx>
åéææï2020-03-01 07:12:58
æääï"çæè" <wenhu.wang@xxxxxxxx>
æéäïwangwenhu <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,trivial@xxxxxxxxxx,Rai Harninder <harninder.rai@xxxxxxx>
äéïRe: Re: [PATCH] powerpc/Kconfig: Make FSL_85XX_CACHE_SRAM configurable>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.

>
Yes, definitely. So like we enable the moulde which should selet 
FSL_85XX_CACHE_SRAM to build vmlinux, FSL_85XX_CACHE_SRAM 
could not be seleted because of the Kconfig definition problem 
which I am trying to fix now.  So would you please merge the patch 
for the convenience of later works depending on the driver.

Wenhu

>-Scott
>
>