[U-Boot] [PATCH] sunxi: improve throughput in the sunxi_mmc driver

[Maxime Ripard]

Hi Jagan,

On Fri, Apr 06, 2018 at 11:36:59AM +0530, Jagan Teki wrote:
> On Wed, Apr 4, 2018 at 12:36 PM, Maxime Ripard
> <maxime.ripard at bootlin.com> wrote:
> > On Wed, Apr 04, 2018 at 12:13:01PM +0530, Jagan Teki wrote:
> >> On Wed, Mar 21, 2018 at 4:48 PM, Maxime Ripard
> >> <maxime.ripard at bootlin.com> wrote:
> >> > From: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
> >> >
> >> > Throughput tests have shown the sunxi_mmc driver to take over 10s to
> >> > read 10MB from a fast eMMC device due to excessive delays in polling
> >> > loops.
> >> >
> >> > This commit restructures the main polling loops to use get_timer(...)
> >> > to determine whether a (millisecond) timeout has expired.  We choose
> >> > not to use the wait_bit function, as we don't need interruptability
> >> > with ctrl-c and have at least one case where two bits (one for an
> >> > error condition and another one for completion) need to be read and
> >> > using wait_bit would have not added to the clarity.
> >> >
> >> > The observed speedup in testing on a A31 is greater than 10x (e.g. a
> >> > 10MB write decreases from 9.302s to 0.884s).
> >>
> >> Fyi: I've seen significant improvement, but not 10x on A64
> >> (bananpi-m64) with read
> >>
> >> Before this change:
> >>
> >> => mmc dev 0
> >> switch to partitions #0, OK
> >> mmc0 is current device
> >> => fatload mmc 0:1 $kernel_addr_r Image
> >> reading Image
> >> 16310784 bytes read in 821 ms (18.9 MiB/s)
> >> => mmc dev 1
> >> switch to partitions #0, OK
> >> mmc1(part 0) is current device
> >> => ext4load mmc 1:1 $kernel_addr_r Image
> >> 16310784 bytes read in 1109 ms (14 MiB/s)
> >>
> >>
> >> After this change:
> >>
> >> => mmc dev 0
> >> switch to partitions #0, OK
> >> mmc0 is current device
> >> => fatload mmc 0:1 $kernel_addr_r Image
> >> 16310784 bytes read in 784 ms (19.8 MiB/s)
> >> => mmc dev 1
> >> switch to partitions #0, OK
> >> mmc1(part 0) is current device
> >> => ext4load mmc 1:1 $kernel_addr_r Image
> >> 16310784 bytes read in 793 ms (19.6 MiB/s)
> >
> > Yeah, the smaller the file is, the bigger the gain is. Since you have
> > an almost twice bigger file, the gains are probably just noise at that
> > point and the bottleneck starts to be your MMC.
> 
> Acked-by: Jagan Teki <jagan at openedev.com>

Jaehoon doesn't seem to reply at all, can we merge this through the
sunxi tree?

Thanks!
Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com