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

[王文虎]

发件人：Scott Wood <oss at buserror.net>
发送日期：2020-03-01 07:12:58
收件人："王文虎" <wenhu.wang at vivo.com>
抄送人：wangwenhu <wenhu.pku at gmail.com>,Kumar Gala <galak at kernel.crashing.org>,Benjamin Herrenschmidt <benh at kernel.crashing.org>,Paul Mackerras <paulus at samba.org>,Michael Ellerman <mpe at ellerman.id.au>,linuxppc-dev at lists.ozlabs.org,linux-kernel at vger.kernel.org,trivial at kernel.org,Rai Harninder <harninder.rai at nxp.com>
主题：Re: Re: [PATCH] powerpc/Kconfig: Make FSL_85XX_CACHE_SRAM configurable>On Tue, 2020-01-21 at 14:38 +0800, 王文虎 wrote:
>> 发件人：Scott Wood <oss at buserror.net>
>> 发送日期：2020-01-21 13:49:59
>> 收件人："王文虎" <wenhu.wang at vivo.com>
>> 抄送人：wangwenhu <wenhu.pku at gmail.com>,Kumar Gala <galak at kernel.crashing.org>,B
>> enjamin Herrenschmidt <benh at kernel.crashing.org>,Paul Mackerras <
>> paulus at samba.org>,Michael Ellerman <mpe at ellerman.id.au>,
>> linuxppc-dev at lists.ozlabs.org,linux-kernel at vger.kernel.org,
>> trivial at kernel.org,Rai Harninder <harninder.rai at nxp.com>
>> 主题：Re: [PATCH] powerpc/Kconfig: Make FSL_85XX_CACHE_SRAM configurable>On
>> Tue, 2020-01-21 at 13:20 +0800, 王文虎 wrote:
>> > > From: Scott Wood <oss at buserror.net>
>> > > Date: 2020-01-21 11:25:25
>> > > To:  wangwenhu <wenhu.pku at gmail.com>,Kumar Gala <
>> > > galak at kernel.crashing.org>,
>> > > Benjamin Herrenschmidt <benh at kernel.crashing.org>,Paul Mackerras <
>> > > paulus at samba.org>,Michael Ellerman <mpe at ellerman.id.au>,
>> > > linuxppc-dev at lists.ozlabs.org,linux-kernel at vger.kernel.org
>> > > Cc:  trivial at kernel.org,wenhu.wang at vivo.com,Rai Harninder <
>> > > harninder.rai at nxp.com>
>> > > 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 at vivo.com>
>> > > > > 
>> > > > > 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 at vivo.com>
>> > > > 
>> > > > 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
>
>