From: Herbert Xu Subject: Re: [PATCH 02/28] crypto: omap-sham: Don't idle/start SHA device between Encrypt operations Date: Tue, 7 Jun 2016 18:08:37 +0800 Message-ID: <20160607100837.GA30875@gondor.apana.org.au> References: <1464771389-10640-1-git-send-email-t-kristo@ti.com> <1464771389-10640-3-git-send-email-t-kristo@ti.com> <574EB091.6040001@ti.com> <574F69D8.1010809@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Grygorii Strashko , tony@atomide.com, Tero Kristo , lokeshvutla@ti.com, linux-crypto@vger.kernel.org, linux-omap@vger.kernel.org, davem@davemloft.net, linux-arm-kernel@lists.infradead.org To: Dave Gerlach Return-path: Content-Disposition: inline In-Reply-To: <574F69D8.1010809@ti.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org List-Id: linux-crypto.vger.kernel.org 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 > >> > >>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 > >>Signed-off-by: Tero Kristo > >>--- > >> 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 Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt