发件人:Scott Wood <o...@buserror.net> 发送日期:2020-01-21 13:49:59 收件人:"王文虎" <wenhu.w...@vivo.com> 抄送人:wangwenhu <wenhu....@gmail.com>,Kumar Gala <ga...@kernel.crashing.org>,Benjamin Herrenschmidt <b...@kernel.crashing.org>,Paul Mackerras <pau...@samba.org>,Michael Ellerman <m...@ellerman.id.au>,linuxppc-dev@lists.ozlabs.org,linux-ker...@vger.kernel.org,triv...@kernel.org,Rai Harninder <harninder....@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 <o...@buserror.net> >> Date: 2020-01-21 11:25:25 >> To: wangwenhu <wenhu....@gmail.com>,Kumar Gala <ga...@kernel.crashing.org>, >> Benjamin Herrenschmidt <b...@kernel.crashing.org>,Paul Mackerras < >> pau...@samba.org>,Michael Ellerman <m...@ellerman.id.au>, >> linuxppc-dev@lists.ozlabs.org,linux-ker...@vger.kernel.org >> Cc: triv...@kernel.org,wenhu.w...@vivo.com,Rai Harninder < >> harninder....@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.w...@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.w...@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. >> > Since this code was added almost ten years ago and there are still no (in- >> > tree?) users of the API, we should just remove the sram code (unless this >> > prods someone to submit such a user very soon). >> > >> >> Yes, pretty long a time. But we DO really use the API now for >> PPCE500/Freescale SoC. > >I do not see any users in the kernel tree. Are you talking about out-of-tree >code, or something that you've submitted or will submit soon? Or are you >accessing it via /dev/mem? > Both, but not submitted yet, and partly under development. >> Like sometimes we need to reset the whole RAM, then the L2-Cache would be >> used as >> SRAM for backup using. Since it is useful for us now, a re-consideration is >> recommanded. > >Where is the code that would do this? > Currently under development, and not submitted yet. >-Scott >> > Wenhu