coresight: tmc: Configure AXI write burst size

The current driver sets the write burst size initiated by TMC-ETR on
AXI bus to a fixed value of 16. Make this configurable by reading the
value specified in fwnode. If not specified, then default to 16.

Introduced a "max_burst_size" variable in tmc_drvdata structure to
facilitate this change.
Signed-off-by: Tanmay Jagdale <tanmay@marvell.com>
Reviewed-by: Mike Leach <mike.leach@linaro.org>
Link: https://lore.kernel.org/r/20210901131049.1365367-3-tanmay@marvell.comSigned-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

drivers/hwtracing/coresight/coresight-tmc-core.c

@@ -432,6 +432,21 @@ static u32 tmc_etr_get_default_buffer_size(struct device *dev)
 	return size;
 }
 
+static u32 tmc_etr_get_max_burst_size(struct device *dev)
+{
+	u32 burst_size;
+
+	if (fwnode_property_read_u32(dev->fwnode, "arm,max-burst-size",
+				     &burst_size))
+		return TMC_AXICTL_WR_BURST_16;
+
+	/* Only permissible values are 0 to 15 */
+	if (burst_size > 0xF)
+		burst_size = TMC_AXICTL_WR_BURST_16;
+
+	return burst_size;
+}
+
 static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
 {
 	int ret = 0;
@@ -469,10 +484,12 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
 	/* This device is not associated with a session */
 	drvdata->pid = -1;
 
-	if (drvdata->config_type == TMC_CONFIG_TYPE_ETR)
+	if (drvdata->config_type == TMC_CONFIG_TYPE_ETR) {
 		drvdata->size = tmc_etr_get_default_buffer_size(dev);
-	else
+		drvdata->max_burst_size = tmc_etr_get_max_burst_size(dev);
+	} else {
 		drvdata->size = readl_relaxed(drvdata->base + TMC_RSZ) * 4;
+	}
 
 	desc.dev = dev;
 	desc.groups = coresight_tmc_groups;

drivers/hwtracing/coresight/coresight-tmc-etr.c

@@ -982,7 +982,8 @@ static void __tmc_etr_enable_hw(struct tmc_drvdata *drvdata)
 
 	axictl = readl_relaxed(drvdata->base + TMC_AXICTL);
 	axictl &= ~TMC_AXICTL_CLEAR_MASK;
-	axictl |= (TMC_AXICTL_PROT_CTL_B1 | TMC_AXICTL_WR_BURST_16);
+	axictl |= TMC_AXICTL_PROT_CTL_B1;
+	axictl |= TMC_AXICTL_WR_BURST(drvdata->max_burst_size);
 	axictl |= TMC_AXICTL_AXCACHE_OS;
 
 	if (tmc_etr_has_cap(drvdata, TMC_ETR_AXI_ARCACHE)) {

drivers/hwtracing/coresight/coresight-tmc.h

@@ -70,7 +70,8 @@
 #define TMC_AXICTL_PROT_CTL_B0	BIT(0)
 #define TMC_AXICTL_PROT_CTL_B1	BIT(1)
 #define TMC_AXICTL_SCT_GAT_MODE	BIT(7)
-#define TMC_AXICTL_WR_BURST_16	0xF00
+#define TMC_AXICTL_WR_BURST(v)	(((v) & 0xf) << 8)
+#define TMC_AXICTL_WR_BURST_16	0xf
 /* Write-back Read and Write-allocate */
 #define TMC_AXICTL_AXCACHE_OS	(0xf << 2)
 #define TMC_AXICTL_ARCACHE_OS	(0xf << 16)
@@ -174,6 +175,8 @@ struct etr_buf {
  * @etr_buf:	details of buffer used in TMC-ETR
  * @len:	size of the available trace for ETF/ETB.
  * @size:	trace buffer size for this TMC (common for all modes).
+ * @max_burst_size: The maximum burst size that can be initiated by
+ *		TMC-ETR on AXI bus.
  * @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.
@@ -198,6 +201,7 @@ struct tmc_drvdata {
 	};
 	u32			len;
 	u32			size;
+	u32			max_burst_size;
 	u32			mode;
 	enum tmc_config_type	config_type;
 	enum tmc_mem_intf_width	memwidth;