Hello, On Thu, Nov 12, 2015 at 7:03 PM, Julian Calaby <julian.cal...@gmail.com> wrote:
> Hi Stefan, > > On Thu, Nov 12, 2015 at 12:20 AM, Stefan Monnier > <monn...@iro.umontreal.ca> wrote: > >> When the CPU clock speed is set to 480 MHz by the U-Boot SPL, > > ^^^ > > You mean MBUS? > > > >> the performance improvement for 'sunxi-fel write' transfers > >> to DRAM is ~95 KB/s -> ~510 KB/s. > > > >> When the CPU clock speed is set to 1008 MHz by the U-Boot SPL, > >> the performance improvement for 'sunxi-fel write' transfers > >> to DRAM is ~180 KB/s -> ~510 KB/s. > > > > I don't understand the relation between the above 2 improvements. > > What change causes the speed to go from 95KB/s to 180KB/s? > > My interpretation of this was that before this change, the transfer > speed was somehow limited by the clock speed. With the MMU enabled, it > appears that the clock speed is no-longer the limiting factor. > > (I'm _guessing_ that the transfer has to bounce through the CPU and > this was slow without the MMU for some reason. I'm also guessing that > enabling the MMU has moved the bottleneck elsewhere - possibly the USB > hardware.) > On A83T board, after enabling MMU, sunxi-fel write speed is similar 510KB/s (peripheral clock is at 600MHz). If I increase the PLL6(peripheral clock), performance is improving. after changing the PLL6 to 1200MHz, transfer speed to DDR3 is : 920.2 KB/s Though, it is mentioned in datasheet that it's value should be 600. However, allwinner u-boot code make it to 1200MHz. > > Thanks, > > -- > Julian Calaby > > Email: julian.cal...@gmail.com > Profile: http://www.google.com/profiles/julian.calaby/ > > -- > You received this message because you are subscribed to the Google Groups > "linux-sunxi" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to linux-sunxi+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "linux-sunxi" group. To unsubscribe from this group and stop receiving emails from it, send an email to linux-sunxi+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
