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Subject[PATCH 2/2] net: macb: Optimize reading HW timestamp
Date
The seconds input from BD (6 bits) just needs to be ORed with the
upper bits from timer in this function. Avoid +/- operations every
single time. Check for seconds rollover at BIT 5 and subtract the
overhead only in that case.

Signed-off-by: Harini Katakam <harini.katakam@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
---
drivers/net/ethernet/cadence/macb_ptp.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_ptp.c b/drivers/net/ethernet/cadence/macb_ptp.c
index e6cb20aaa76a..674002661366 100644
--- a/drivers/net/ethernet/cadence/macb_ptp.c
+++ b/drivers/net/ethernet/cadence/macb_ptp.c
@@ -247,6 +247,7 @@ static int gem_hw_timestamp(struct macb *bp, u32 dma_desc_ts_1,
u32 dma_desc_ts_2, struct timespec64 *ts)
{
struct timespec64 tsu;
+ bool sec_rollover = false;

ts->tv_sec = (GEM_BFEXT(DMA_SECH, dma_desc_ts_2) << GEM_DMA_SECL_SIZE) |
GEM_BFEXT(DMA_SECL, dma_desc_ts_1);
@@ -264,9 +265,12 @@ static int gem_hw_timestamp(struct macb *bp, u32 dma_desc_ts_1,
*/
if ((ts->tv_sec & (GEM_DMA_SEC_TOP >> 1)) &&
!(tsu.tv_sec & (GEM_DMA_SEC_TOP >> 1)))
- ts->tv_sec -= GEM_DMA_SEC_TOP;
+ sec_rollover = true;
+
+ ts->tv_sec |= ((~GEM_DMA_SEC_MASK) & tsu.tv_sec);

- ts->tv_sec += ((~GEM_DMA_SEC_MASK) & tsu.tv_sec);
+ if (sec_rollover)
+ ts->tv_sec -= GEM_DMA_SEC_TOP;

return 0;
}
--
2.17.1
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