linux-kernel - [PATCH V4 14/18] coresight: tmc: keep track of memory width

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Date:	Tue, 26 Apr 2016 16:10:30 -0600
From:	Mathieu Poirier <mathieu.poirier@...aro.org>
To:	linux-arm-kernel@...ts.infradead.org, Suzuki.Poulose@....com
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH V4 14/18] coresight: tmc: keep track of memory width

Accessing the HW configuration register each time the memory
width is needed simply doesn't make sense.  It is much more
efficient to read the value once and keep a reference for
later use.

Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
---
 drivers/hwtracing/coresight/coresight-tmc-etf.c | 14 +---------
 drivers/hwtracing/coresight/coresight-tmc.c     | 34 +++++++++++++++++++++++++
 drivers/hwtracing/coresight/coresight-tmc.h     | 10 +++++---
 3 files changed, 41 insertions(+), 17 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index b11c52be54a9..ba3384781f71 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -41,25 +41,13 @@ void tmc_etb_enable_hw(struct tmc_drvdata *drvdata)
 
 static void tmc_etb_dump_hw(struct tmc_drvdata *drvdata)
 {
-	enum tmc_mem_intf_width memwidth;
-	u8 memwords;
 	char *bufp;
 	u32 read_data;
 	int i;
 
-	memwidth = BMVAL(readl_relaxed(drvdata->base + CORESIGHT_DEVID), 8, 10);
-	if (memwidth == TMC_MEM_INTF_WIDTH_32BITS)
-		memwords = 1;
-	else if (memwidth == TMC_MEM_INTF_WIDTH_64BITS)
-		memwords = 2;
-	else if (memwidth == TMC_MEM_INTF_WIDTH_128BITS)
-		memwords = 4;
-	else
-		memwords = 8;
-
 	bufp = drvdata->buf;
 	while (1) {
-		for (i = 0; i < memwords; i++) {
+		for (i = 0; i < drvdata->memwidth; i++) {
 			read_data = readl_relaxed(drvdata->base + TMC_RRD);
 			if (read_data == 0xFFFFFFFF)
 				return;
diff --git a/drivers/hwtracing/coresight/coresight-tmc.c b/drivers/hwtracing/coresight/coresight-tmc.c
index ae7525a2b94a..9e02ac963cd0 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.c
+++ b/drivers/hwtracing/coresight/coresight-tmc.c
@@ -186,6 +186,39 @@ static const struct file_operations tmc_fops = {
 	.llseek		= no_llseek,
 };
 
+static enum tmc_mem_intf_width tmc_get_memwidth(u32 devid)
+{
+	enum tmc_mem_intf_width memwidth;
+
+	/*
+	 * Excerpt from the TRM:
+	 *
+	 * DEVID::MEMWIDTH[10:8]
+	 * 0x2 Memory interface databus is 32 bits wide.
+	 * 0x3 Memory interface databus is 64 bits wide.
+	 * 0x4 Memory interface databus is 128 bits wide.
+	 * 0x5 Memory interface databus is 256 bits wide.
+	 */
+	switch (BMVAL(devid, 8, 10)) {
+	case 0x2:
+		memwidth = TMC_MEM_INTF_WIDTH_32BITS;
+		break;
+	case 0x3:
+		memwidth = TMC_MEM_INTF_WIDTH_64BITS;
+		break;
+	case 0x4:
+		memwidth = TMC_MEM_INTF_WIDTH_128BITS;
+		break;
+	case 0x5:
+		memwidth = TMC_MEM_INTF_WIDTH_256BITS;
+		break;
+	default:
+		memwidth = 0;
+	}
+
+	return memwidth;
+}
+
 #define coresight_tmc_simple_func(name, offset)			\
 	coresight_simple_func(struct tmc_drvdata, name, offset)
 
@@ -299,6 +332,7 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
 
 	devid = readl_relaxed(drvdata->base + CORESIGHT_DEVID);
 	drvdata->config_type = BMVAL(devid, 6, 7);
+	drvdata->memwidth = tmc_get_memwidth(devid);
 
 	if (drvdata->config_type == TMC_CONFIG_TYPE_ETR) {
 		if (np)
diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
index 94bc034d3b98..c5d06fd57fa8 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h
@@ -81,10 +81,10 @@ enum tmc_mode {
 };
 
 enum tmc_mem_intf_width {
-	TMC_MEM_INTF_WIDTH_32BITS	= 0x2,
-	TMC_MEM_INTF_WIDTH_64BITS	= 0x3,
-	TMC_MEM_INTF_WIDTH_128BITS	= 0x4,
-	TMC_MEM_INTF_WIDTH_256BITS	= 0x5,
+	TMC_MEM_INTF_WIDTH_32BITS	= 1,
+	TMC_MEM_INTF_WIDTH_64BITS	= 2,
+	TMC_MEM_INTF_WIDTH_128BITS	= 4,
+	TMC_MEM_INTF_WIDTH_256BITS	= 8,
 };
 
 /**
@@ -100,6 +100,7 @@ enum tmc_mem_intf_width {
  * @size:	@buf size.
  * @mode:	how this TMC is being used.
  * @config_type: TMC variant, must be of type @tmc_config_type.
+ * @memwidth:	width of the memory interface databus, in bytes.
  * @trigger_cntr: amount of words to store after a trigger.
  */
 struct tmc_drvdata {
@@ -115,6 +116,7 @@ struct tmc_drvdata {
 	u32			size;
 	local_t			mode;
 	enum tmc_config_type	config_type;
+	enum tmc_mem_intf_width	memwidth;
 	u32			trigger_cntr;
 };
 
-- 
2.5.0