Hi Sudhakar, On Fri, Jan 20, 2012 at 11:01 AM, Rajashekhara, Sudhakar <sudhakar....@ti.com> wrote: > Hi Christian, > > On Tue, Jan 17, 2012 at 18:23:52, Christian Riesch wrote: >> Hi Sudhakar, hi Mike, >> >> On Tue, Jan 17, 2012 at 1:43 PM, Michael Williamson >> <michael.william...@criticallink.com> wrote: >> > On 1/17/2012 12:39 AM, Rajashekhara, Sudhakar wrote: > > [...] > >> > >> > Well, that's all fine and swell, except we have OMAP-L138 platforms >> > (built using the MityDSP-L138 SOM) that use the EMIFA for other >> > devices than NAND, such as an FPGA (and no SDRAM). Dropping the default >> > 300 MHz OPP EMIFA speed from 100 MHz down to 60 MHz will directly translate >> > to a 40% reduction in potential bus bandwidth. If you are making this >> > device >> > wide, it would really be nice to have an option that is more consistent >> > with option A and let the platform designer decide what rate the EMIFA >> > clock should run at based on his hardware requirements. >> >> In my opinion hardcoding OPPs in a SoC specific file >> (arch/arm/mach-davinci/da850.c) was a bad idea. Setting EMIFA clock to >> 1/5 of CPU rate may be fine for some boards, but for others it may be >> a bad decision. How about boards with input clock frequencies other >> than 24 MHz? Currently the OPP settings are only correct if a 24 MHz >> quartz or oscillator is used. So I think the OPPs should move out of >> the SoC specific file. >> > > Using a different oscillator is a perfectly valid use case but I was > wondering why anyone would do that? The OPP settings are defined and > are valid when using a 24 MHz quartz. Have you come across a board > where a different quartz is being used with OMAP-L138?
Yes, my own board. I already had a 25MHz clock on the board so I used it to drive the SoC as well and saved a few components. However, I do not use frequency/voltage scaling, so there was no need to change the OPP configurations. I just want to point out that there are such use cases and if work on the OPP settings is done, it should be done in a way that allows other input clock frequencies than just 24 MHz. Regards, Christian _______________________________________________ Davinci-linux-open-source mailing list Davinci-linux-open-source@linux.davincidsp.com http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source
