From: Vignesh Raghavendra <vigneshr@xxxxxx> 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@xxxxxx> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx> --- drivers/dma/ti/k3-udma.c | 80 ++++++++++++++++++++++++++-------------- 1 file changed, 53 insertions(+), 27 deletions(-) diff --git a/drivers/dma/ti/k3-udma.c b/drivers/dma/ti/k3-udma.c index ea79c2df28e0..fb59c869a6a7 100644 --- a/drivers/dma/ti/k3-udma.c +++ b/drivers/dma/ti/k3-udma.c @@ -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; + 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 (uc->desc) { - residue_diff = uc->tx_drain.residue; - jiffie_diff = uc->tx_drain.jiffie; - desc_done = udma_is_desc_really_done(uc, uc->desc); - } - - if (!desc_done) { - jiffie_diff = uc->tx_drain.jiffie - jiffie_diff; - 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; - } else { - /* No progress, check again in 1 second */ - delay = HZ; + if (!desc_done) { + /* + * 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 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 */ + schedule_delayed_work(&uc->tx_drain.work, HZ); + break; + } + + usleep_range(ktime_to_us(delay), + ktime_to_us(delay) + 10); + continue; } - schedule_delayed_work(&uc->tx_drain.work, delay); - } else if (uc->desc) { - struct udma_desc *d = uc->desc; + if (uc->desc) { + struct udma_desc *d = uc->desc; + + uc->bcnt += d->residue; + udma_start(uc); + vchan_cookie_complete(&d->vd); + break; + } - uc->bcnt += d->residue; - udma_start(uc); - vchan_cookie_complete(&d->vd); + break; } } -- Peter Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki