[PATCH 02/28] crypto: omap-sham: Don't idle/start SHA device between Encrypt operations

[Herbert Xu]

On Wed, Jun 01, 2016 at 06:03:52PM -0500, Dave Gerlach wrote:
> On 06/01/2016 04:53 AM, Grygorii Strashko wrote:
> >On 06/01/2016 11:56 AM, Tero Kristo wrote:
> >>From: Lokesh Vutla <lokeshvutla at ti.com>
> >>
> >>Calling runtime PM API for every block causes serious perf hit to
> >>crypto operations that are done on a long buffer.
> >>As crypto is performed on a page boundary, encrypting large buffers can
> >>cause a series of crypto operations divided by page. The runtime PM API
> >>is also called those many times.
> >>
> >>We call runtime_pm_get_sync only at beginning on the session (cra_init)
> >>and runtime_pm_put at the end. This result in upto a 50% speedup.
> >>This doesn't make the driver to keep the system awake as runtime get/put
> >>is only called during a crypto session which completes usually quickly.
> >>
> >>Signed-off-by: Lokesh Vutla <lokeshvutla at ti.com>
> >>Signed-off-by: Tero Kristo <t-kristo at ti.com>
> >>---
> >>  drivers/crypto/omap-sham.c | 27 +++++++++++++++++----------
> >>  1 file changed, 17 insertions(+), 10 deletions(-)
> >>
> >>diff --git a/drivers/crypto/omap-sham.c b/drivers/crypto/omap-sham.c
> >>index 6eefaa2..bd0258f 100644
> >>--- a/drivers/crypto/omap-sham.c
> >>+++ b/drivers/crypto/omap-sham.c
> >>@@ -360,14 +360,6 @@ static void omap_sham_copy_ready_hash(struct
> >>ahash_request *req)
> >>
> >>  static int omap_sham_hw_init(struct omap_sham_dev *dd)
> >>  {
> >>-    int err;
> >>-
> >>-    err = pm_runtime_get_sync(dd->dev);
> >>-    if (err < 0) {
> >>-        dev_err(dd->dev, "failed to get sync: %d\n", err);
> >>-        return err;
> >>-    }
> >>-
> 
> Would it be worth it to investigate a pm_runtime autosuspend
> approach rather than knocking runtime PM out here completely? I am
> not clear if the overhead is coming from the pm_runtime calls
> themselves or the actual idling of the IP, but if it's the idling of
> the IP causing the slowdown, with a large enough autosuspend_delay
> we don't actually sleep between each block but after a long enough
> period of idle time we would actually suspend.

Indeed, I think this patch is bogus.  cra_init is associated
with the tfm object which is usually long-lived.  So doing power
management there makes no sense.

Cheers,
-- 
Email: Herbert Xu <herbert at gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt