On 7/27/22 17:08, Vaishnav Achath wrote:
> UDMA_CHAN_RT_*BCNT_REG stores the real-time channel bytecount statistics.
> These registers are 32-bit hardware counters and the driver uses these
> counters to monitor the operational progress status for a channel, when
> transferring more than 4GB of data it was observed that these counters
> overflow and completion calculation of a operation gets affected and the
> transfer hangs indefinitely.
>
> This commit adds changes to decrease the byte count for every complete
> transaction so that these registers never overflow and the proper byte
> count statistics is maintained for ongoing transaction by the RT counters.
>
> Earlier uc->bcnt used to maintain a count of the completed bytes at driver
> side, since the RT counters maintain the statistics of current transaction
> now, the maintenance of uc->bcnt is not necessary.
>
> Signed-off-by: Vaishnav Achath <vaishnav.a@xxxxxx>
> ---
> V1->V2 :
> * Update bcnt reset based on uc->desc->dir
> * change order of udma_decrement_byte_counters() to before udma_start()
> * update subsystem tag
>
> drivers/dma/ti/k3-udma.c | 25 +++++++++++++++++--------
> 1 file changed, 17 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/dma/ti/k3-udma.c b/drivers/dma/ti/k3-udma.c
> index 2f0d2c68c93c..39b330ada200 100644
> --- a/drivers/dma/ti/k3-udma.c
> +++ b/drivers/dma/ti/k3-udma.c
> @@ -300,8 +300,6 @@ struct udma_chan {
>
> struct udma_tx_drain tx_drain;
>
> - u32 bcnt; /* number of bytes completed since the start of the channel */
> -
> /* Channel configuration parameters */
> struct udma_chan_config config;
>
> @@ -757,6 +755,20 @@ static void udma_reset_rings(struct udma_chan *uc)
> }
> }
>
> +static void udma_decrement_byte_counters(struct udma_chan *uc, u32 val)
> +{
> + if (uc->desc->dir == DMA_DEV_TO_MEM && uc->rchan) {
if the dir is DMA_DEV_TO_MEM then we have rchan, no need for checking it.
> + udma_rchanrt_write(uc, UDMA_CHAN_RT_BCNT_REG, val);
> + udma_rchanrt_write(uc, UDMA_CHAN_RT_SBCNT_REG, val);
> + udma_rchanrt_write(uc, UDMA_CHAN_RT_PEER_BCNT_REG, val);
> + } else if (uc->tchan) {
in other directions (MEM_TO_DEV, MEM_TO_MEM) we have tchan.
> + udma_tchanrt_write(uc, UDMA_CHAN_RT_BCNT_REG, val);
> + udma_tchanrt_write(uc, UDMA_CHAN_RT_SBCNT_REG, val);
> + if (!uc->bchan)
> + udma_tchanrt_write(uc, UDMA_CHAN_RT_PEER_BCNT_REG, val);
> + }
> +}
Thus we only need this type of decision:
if (uc->desc->dir == DMA_DEV_TO_MEM) {
udma_rchanrt_write(uc, UDMA_CHAN_RT_BCNT_REG, val);
udma_rchanrt_write(uc, UDMA_CHAN_RT_SBCNT_REG, val);
udma_rchanrt_write(uc, UDMA_CHAN_RT_PEER_BCNT_REG, val);
} else {
udma_tchanrt_write(uc, UDMA_CHAN_RT_BCNT_REG, val);
udma_tchanrt_write(uc, UDMA_CHAN_RT_SBCNT_REG, val);
if (!uc->bchan)
udma_tchanrt_write(uc, UDMA_CHAN_RT_PEER_BCNT_REG, val);
}
> +
> static void udma_reset_counters(struct udma_chan *uc)
> {
> u32 val;
> @@ -790,8 +802,6 @@ static void udma_reset_counters(struct udma_chan *uc)
> val = udma_rchanrt_read(uc, UDMA_CHAN_RT_PEER_BCNT_REG);
> udma_rchanrt_write(uc, UDMA_CHAN_RT_PEER_BCNT_REG, val);
> }
> -
> - uc->bcnt = 0;
> }
>
> static int udma_reset_chan(struct udma_chan *uc, bool hard)
> @@ -1115,7 +1125,7 @@ static void udma_check_tx_completion(struct work_struct *work)
> if (uc->desc) {
> struct udma_desc *d = uc->desc;
>
> - uc->bcnt += d->residue;
> + udma_decrement_byte_counters(uc, d->residue);
> udma_start(uc);
> vchan_cookie_complete(&d->vd);
> break;
> @@ -1168,7 +1178,7 @@ static irqreturn_t udma_ring_irq_handler(int irq, void *data)
> vchan_cyclic_callback(&d->vd);
> } else {
> if (udma_is_desc_really_done(uc, d)) {
> - uc->bcnt += d->residue;
> + udma_decrement_byte_counters(uc, d->residue);
> udma_start(uc);
> vchan_cookie_complete(&d->vd);
> } else {
> @@ -1204,7 +1214,7 @@ static irqreturn_t udma_udma_irq_handler(int irq, void *data)
> vchan_cyclic_callback(&d->vd);
> } else {
> /* TODO: figure out the real amount of data */
> - uc->bcnt += d->residue;
> + udma_decrement_byte_counters(uc, d->residue);
> udma_start(uc);
> vchan_cookie_complete(&d->vd);
> }
> @@ -3809,7 +3819,6 @@ static enum dma_status udma_tx_status(struct dma_chan *chan,
> bcnt = udma_tchanrt_read(uc, UDMA_CHAN_RT_BCNT_REG);
> }
>
> - bcnt -= uc->bcnt;
> if (bcnt && !(bcnt % uc->desc->residue))
> residue = 0;
> else
--
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