From: Vinod Koul <vkoul@kernel.org>
To: Vignesh Raghavendra <vigneshr@ti.com>
Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>,
dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org,
dan.j.williams@intel.com, grygorii.strashko@ti.com
Subject: Re: [PATCH for-next 1/4] dmaengine: ti: k3-udma: Use ktime/usleep_range based TX completion check
Date: Tue, 28 Jan 2020 18:14:03 +0530 [thread overview]
Message-ID: <20200128124403.GV2841@vkoul-mobl> (raw)
In-Reply-To: <d968f32d-dc5f-0567-5aa4-faf318025c23@ti.com>
On 28-01-20, 17:35, Vignesh Raghavendra wrote:
> >> + /* Transfer is incomplete, store current residue and time stamp */
> >> if (peer_bcnt < bcnt) {
> >> uc->tx_drain.residue = bcnt - peer_bcnt;
> >> - uc->tx_drain.jiffie = jiffies;
> >> + uc->tx_drain.tstamp = ktime_get();
> >
> > Any reason why ktime_get() is better than jiffies..?
>
> Resolution of jiffies is 4ms. ktime_t is has better resolution (upto ns
> scale). With jiffies, I observed that code was either always polling DMA
> progress counters (which affects HW data transfer speed) or sleeping too
> long, both causing performance loss. Switching to ktime_t provides
> better prediction of how long transfer takes to complete.
Thanks for explanation, i think it is good info to add in changelog.
--
~Vinod
next prev parent reply other threads:[~2020-01-28 12:44 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-27 13:21 [PATCH for-next 0/4] dmaengine: ti: k3-udma: Updates for next Peter Ujfalusi
2020-01-27 13:21 ` [PATCH for-next 1/4] dmaengine: ti: k3-udma: Use ktime/usleep_range based TX completion check Peter Ujfalusi
2020-01-28 11:48 ` Vinod Koul
2020-01-28 12:05 ` Vignesh Raghavendra
2020-01-28 12:44 ` Vinod Koul [this message]
2020-02-11 10:13 ` Peter Ujfalusi
2020-01-27 13:21 ` [PATCH for-next 2/4] dmaengine: ti: k3-udma: Workaround for RX teardown with stale data in peer Peter Ujfalusi
2020-01-27 13:21 ` [PATCH for-next 3/4] dmaengine: ti: k3-udma: Move the TR counter calculation to helper function Peter Ujfalusi
2020-01-27 13:21 ` [PATCH for-next 4/4] dmaengine: ti: k3-udma: Use the TR counter helper for slave_sg and cyclic Peter Ujfalusi
2020-01-28 10:15 ` [PATCH for-next 0/4] dmaengine: ti: k3-udma: Updates for next Peter Ujfalusi
2020-01-28 11:50 ` Vinod Koul
2020-01-28 12:37 ` Peter Ujfalusi
2020-01-30 13:19 ` Peter Ujfalusi
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