> From: [email protected] [mailto:linux-omap- > [email protected]] On Behalf Of Grazvydas Ignotas > Sent: Tuesday, April 10, 2012 7:30 PM
> What I think is going on here is that omap_sram_idle() is taking too > much time because it's overhead is too large. I've added a counter > there and it seems to be called ~530 times per megabyte (DMA operates > in ~2K chunks so it makes sense), that's over 2000 calls per second. > Some quick measurement code shows ~243us spent for setting up in > omap_sram_idle() (before and after omap34xx_do_sram_idle()). 243uS is really a long time for C1. For some reason has grown a lot since last time I captured path in ETM. Your analysis correlates well to reports from a couple years back. N900 folks did report that the non-clock gated C1 was needed (as exists in code today). IIRC the NAND stack did have small-uS spins on NAND status or something which having higher clock stop penalty resulted in big performance dip. You needed like <10uS for C1 or bit hit. Regards, Richard W. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
