linux-kernel - [PATCH 2/2] dmaengine: pl330: don't emit code for one iteration loop

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Message-Id: <1492180531-1780-3-git-send-email-al.kochet@gmail.com>
Date:   Fri, 14 Apr 2017 17:35:30 +0300
From:   Alexander Kochetkov <al.kochet@...il.com>
To:     Dan Williams <dan.j.williams@...el.com>,
        Vinod Koul <vinod.koul@...el.com>, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        hhb@...k-chips.com, shawn.lin@...k-chips.com,
        caesar.wang@...k-chips.com, sugar.zhang@...k-chips.com,
        ulysses.huang@...k-chips.com
Cc:     Alexander Kochetkov <al.kochet@...il.com>
Subject: [PATCH 2/2] dmaengine: pl330: don't emit code for one iteration loop

The patch remove one iteration outer loop in the _loop().
Removing loop saves 4 bytes of MicroCode buffer. This
savings make sense for free-running cyclic transfer
implementation.

    DMALP_0 0
    ...
    DMALPENDA_0 bjmpto_9

Signed-off-by: Alexander Kochetkov <al.kochet@...il.com>
---
 drivers/dma/pl330.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index 56a2377..6126dde 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -1268,7 +1268,7 @@ static inline int _loop(struct pl330_dmac *pl330, unsigned dry_run, u8 buf[],
 	lpend.bjump = 0;
 	szlpend = _emit_LPEND(1, buf, &lpend);
 
-	if (lcnt0) {
+	if (lcnt0 > 1) {
 		szlp *= 2;
 		szlpend *= 2;
 	}
@@ -1284,7 +1284,7 @@ static inline int _loop(struct pl330_dmac *pl330, unsigned dry_run, u8 buf[],
 
 	off = 0;
 
-	if (lcnt0) {
+	if (lcnt0 > 1) {
 		off += _emit_LP(dry_run, &buf[off], 0, lcnt0);
 		ljmp0 = off;
 	}
@@ -1300,7 +1300,7 @@ static inline int _loop(struct pl330_dmac *pl330, unsigned dry_run, u8 buf[],
 	lpend.bjump = off - ljmp1;
 	off += _emit_LPEND(dry_run, &buf[off], &lpend);
 
-	if (lcnt0) {
+	if (lcnt0 > 1) {
 		lpend.cond = ALWAYS;
 		lpend.forever = false;
 		lpend.loop = 0;
@@ -1309,7 +1309,7 @@ static inline int _loop(struct pl330_dmac *pl330, unsigned dry_run, u8 buf[],
 	}
 
 	*bursts = lcnt1 * cyc;
-	if (lcnt0)
+	if (lcnt0 > 1)
 		*bursts *= lcnt0;
 
 	return off;
-- 
1.7.9.5