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dmaengine: ti: k3-udma: Use ktime/usleep_range based TX completion check

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In some cases (McSPI for example) the jiffie and delayed_work based
workaround can cause big throughput drop.

Switch to use ktime/usleep_range based implementation to be able
to sustain speed for PDMA based peripherals.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20200214091441.27535-2-peter.ujfalusi@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
This commit is contained in:
Vignesh Raghavendra 2020-02-14 11:14:36 +02:00 committed by Vinod Koul
parent 2227ab4216
commit 1c83767c9d
1 changed files with 53 additions and 27 deletions
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52
drivers/dma/ti/k3-udma.c
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@ -5,6 +5,7 @@
*/
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/dmapool.h>
@ -169,7 +170,7 @@ enum udma_chan_state {
struct udma_tx_drain {
struct delayed_work work;
unsigned long jiffie;
ktime_t tstamp;
u32 residue;
};
@ -946,9 +947,10 @@ static bool udma_is_desc_really_done(struct udma_chan *uc, struct udma_desc *d)
peer_bcnt = udma_tchanrt_read(uc->tchan, UDMA_TCHAN_RT_PEER_BCNT_REG);
bcnt = udma_tchanrt_read(uc->tchan, UDMA_TCHAN_RT_BCNT_REG);
/* 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();
return false;
}
@ -961,35 +963,59 @@ static void udma_check_tx_completion(struct work_struct *work)
tx_drain.work.work);
bool desc_done = true;
u32 residue_diff;
unsigned long jiffie_diff, delay;
ktime_t time_diff;
unsigned long delay;
while (1) {
if (uc->desc) {
/* Get previous residue and time stamp */
residue_diff = uc->tx_drain.residue;
jiffie_diff = uc->tx_drain.jiffie;
time_diff = uc->tx_drain.tstamp;
/*
* Get current residue and time stamp or see if
* transfer is complete
*/
desc_done = udma_is_desc_really_done(uc, uc->desc);
}
if (!desc_done) {
jiffie_diff = uc->tx_drain.jiffie - jiffie_diff;
/*
* Find the time delta and residue delta w.r.t
* previous poll
*/
time_diff = ktime_sub(uc->tx_drain.tstamp,
time_diff) + 1;
residue_diff -= uc->tx_drain.residue;
if (residue_diff) {
/* Try to guess when we should check next time */
residue_diff /= jiffie_diff;
delay = uc->tx_drain.residue / residue_diff / 3;
if (jiffies_to_msecs(delay) < 5)
delay = 0;
/*
* Try to guess when we should check
* next time by calculating rate at
* which data is being drained at the
* peer device
*/
delay = (time_diff / residue_diff) *
uc->tx_drain.residue;
} else {
/* No progress, check again in 1 second */
delay = HZ;
schedule_delayed_work(&uc->tx_drain.work, HZ);
break;
}
schedule_delayed_work(&uc->tx_drain.work, delay);
} else if (uc->desc) {
usleep_range(ktime_to_us(delay),
ktime_to_us(delay) + 10);
continue;
}
if (uc->desc) {
struct udma_desc *d = uc->desc;
uc->bcnt += d->residue;
udma_start(uc);
vchan_cookie_complete(&d->vd);
break;
}
break;
}
}