On Mon, Sep 14, 2015 at 03:31:05PM +0300, Peter Ujfalusi wrote: > From: Misael Lopez Cruz <misael.lopez@xxxxxx> > > The L3 throughput can be higher than expected when packed access > is not enabled. The ratio depends on the number of bytes in a > transaction and the EMIF interface width. > > The throughput was measured for the following settings/cases: > > * Case 1: Burst size of 64 bytes, packed access disabled > * Case 2: Burst size of 64 bytes, packed access enabled > * Case 3: Burst disabled, packed access disabled > > Throughput measurements were done during McASP-based audio > playback on the Jacinto6 EVM using the omapconf tool [1]: > $ omapconf trace bw -m sdma_rd > > --------------------------------------------------------- > Throughput (MB/s) > Audio parameters Case 1 Case 2 Case 3 > --------------------------------------------------------- > 44.1kHz, 16-bits, stereo 1.41 0.18 1.41 > 44.1kHz, 32-bits, stereo 1.41 0.35 1.41 > 44.1kHz, 16-bits, 4-chan 2.82 0.35 2.82 > 44.1kHz, 16-bits, 6-chan 4.23 0.53 4.23 > 44.1kHz, 16-bits, 8-chan 5.64 0.71 5.64 > --------------------------------------------------------- > > From above measurements, case 2 is the only one that delivers > the expected throughput for the given audio parameters. For > that reason, the packed accesses are now enabled. > > It's worth to mention that packed accesses cannot be enabled > for all addressing modes. In cyclic transfers, it can be > enabled in the source for MEM_TO_DEV and in dest for DEV_TO_MEM, > as they use post-increment mode which supports packed accesses. > > Peter Ujfalusi: > From the TRM regarding to this: > "NOTE: Except in the constant addressing mode, the source or > destination must be specified as packed for burst transactions > to occur." > > So w/o the packed setting the burst on the MEM side was not > enabled, this explains the numbers. > > [1] https://github.com/omapconf/omapconf > Applied, thanks -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
