linux-kernel - [PATCH v2 2/6] soc/fsl/qe: qe.c: reduce static memory footprint by 1.7K

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Message-ID: <20190501092841.9026-3-rasmus.villemoes@prevas.dk>
Date:   Wed, 1 May 2019 09:29:05 +0000
From:   Rasmus Villemoes <rasmus.villemoes@...vas.dk>
To:     "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Qiang Zhao <qiang.zhao@....com>, Li Yang <leoyang.li@....com>
CC:     "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Scott Wood <oss@...error.net>,
        Christophe Leroy <christophe.leroy@....fr>,
        Mark Rutland <mark.rutland@....com>,
        Rasmus Villemoes <Rasmus.Villemoes@...vas.se>
Subject: [PATCH v2 2/6] soc/fsl/qe: qe.c: reduce static memory footprint by
 1.7K

The current array of struct qe_snum use 256*4 bytes for just keeping
track of the free/used state of each index, and the struct layout
means there's another 768 bytes of padding. If we just unzip that
structure, the array of snum values just use 256 bytes, while the
free/inuse state can be tracked in a 32 byte bitmap.

So this reduces the .data footprint by 1760 bytes. It also serves as
preparation for introducing another DT binding for specifying the snum
values.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@...vas.dk>
---
 drivers/soc/fsl/qe/qe.c | 43 ++++++++++++-----------------------------
 1 file changed, 12 insertions(+), 31 deletions(-)

diff --git a/drivers/soc/fsl/qe/qe.c b/drivers/soc/fsl/qe/qe.c
index 855373deb746..303aa29cb27d 100644
--- a/drivers/soc/fsl/qe/qe.c
+++ b/drivers/soc/fsl/qe/qe.c
@@ -14,6 +14,7 @@
  * Free Software Foundation;  either version 2 of the  License, or (at your
  * option) any later version.
  */
+#include <linux/bitmap.h>
 #include <linux/errno.h>
 #include <linux/sched.h>
 #include <linux/kernel.h>
@@ -43,25 +44,14 @@ static DEFINE_SPINLOCK(qe_lock);
 DEFINE_SPINLOCK(cmxgcr_lock);
 EXPORT_SYMBOL(cmxgcr_lock);
 
-/* QE snum state */
-enum qe_snum_state {
-	QE_SNUM_STATE_USED,
-	QE_SNUM_STATE_FREE
-};
-
-/* QE snum */
-struct qe_snum {
-	u8 num;
-	enum qe_snum_state state;
-};
-
 /* We allocate this here because it is used almost exclusively for
  * the communication processor devices.
  */
 struct qe_immap __iomem *qe_immr;
 EXPORT_SYMBOL(qe_immr);
 
-static struct qe_snum snums[QE_NUM_OF_SNUM];	/* Dynamically allocated SNUMs */
+static u8 snums[QE_NUM_OF_SNUM];	/* Dynamically allocated SNUMs */
+static DECLARE_BITMAP(snum_state, QE_NUM_OF_SNUM);
 static unsigned int qe_num_of_snum;
 
 static phys_addr_t qebase = -1;
@@ -315,10 +305,8 @@ static void qe_snums_init(void)
 	else
 		snum_init = snum_init_46;
 
-	for (i = 0; i < qe_num_of_snum; i++) {
-		snums[i].num = snum_init[i];
-		snums[i].state = QE_SNUM_STATE_FREE;
-	}
+	bitmap_zero(snum_state, QE_NUM_OF_SNUM);
+	memcpy(snums, snum_init, qe_num_of_snum);
 }
 
 int qe_get_snum(void)
@@ -328,12 +316,10 @@ int qe_get_snum(void)
 	int i;
 
 	spin_lock_irqsave(&qe_lock, flags);
-	for (i = 0; i < qe_num_of_snum; i++) {
-		if (snums[i].state == QE_SNUM_STATE_FREE) {
-			snums[i].state = QE_SNUM_STATE_USED;
-			snum = snums[i].num;
-			break;
-		}
+	i = find_first_zero_bit(snum_state, qe_num_of_snum);
+	if (i < qe_num_of_snum) {
+		set_bit(i, snum_state);
+		snum = snums[i];
 	}
 	spin_unlock_irqrestore(&qe_lock, flags);
 
@@ -343,14 +329,9 @@ EXPORT_SYMBOL(qe_get_snum);
 
 void qe_put_snum(u8 snum)
 {
-	int i;
-
-	for (i = 0; i < qe_num_of_snum; i++) {
-		if (snums[i].num == snum) {
-			snums[i].state = QE_SNUM_STATE_FREE;
-			break;
-		}
-	}
+	const u8 *p = memchr(snums, snum, qe_num_of_snum);
+	if (p)
+		clear_bit(p - snums, snum_state);
 }
 EXPORT_SYMBOL(qe_put_snum);
 
-- 
2.20.1