memory: tegra20: Add debug statistics

Add debug statistics collection support. The statistics is available
via debugfs in '/sys/kernel/debug/mc/stats', it shows percent of memory
controller utilization for each memory client. This information is
intended to help with debugging of memory performance issues, it already
was proven to be useful by helping to improve memory bandwidth management
of the display driver.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210319130933.23261-1-digetx@gmail.com

drivers/memory/tegra/mc.c

@@ -827,6 +827,15 @@ static int tegra_mc_probe(struct platform_device *pdev)
 		return err;
 	}
 
+	mc->debugfs.root = debugfs_create_dir("mc", NULL);
+
+	if (mc->soc->init) {
+		err = mc->soc->init(mc);
+		if (err < 0)
+			dev_err(&pdev->dev, "failed to initialize SoC driver: %d\n",
+				err);
+	}
+
 	err = tegra_mc_reset_setup(mc);
 	if (err < 0)
 		dev_err(&pdev->dev, "failed to register reset controller: %d\n",

drivers/memory/tegra/mc.h

@@ -92,12 +92,12 @@ icc_provider_to_tegra_mc(struct icc_provider *provider)
 	return container_of(provider, struct tegra_mc, provider);
 }
 
-static inline u32 mc_readl(struct tegra_mc *mc, unsigned long offset)
+static inline u32 mc_readl(const struct tegra_mc *mc, unsigned long offset)
 {
 	return readl_relaxed(mc->regs + offset);
 }
 
-static inline void mc_writel(struct tegra_mc *mc, u32 value,
+static inline void mc_writel(const struct tegra_mc *mc, u32 value,
 			     unsigned long offset)
 {
 	writel_relaxed(value, mc->regs + offset);

drivers/memory/tegra/tegra20.c

@@ -3,6 +3,8 @@
  * Copyright (C) 2012 NVIDIA CORPORATION.  All rights reserved.
  */
 
+#include <linux/bitfield.h>
+#include <linux/delay.h>
 #include <linux/of_device.h>
 #include <linux/slab.h>
 #include <linux/string.h>
@@ -11,6 +13,77 @@
 
 #include "mc.h"
 
+#define MC_STAT_CONTROL				0x90
+#define MC_STAT_EMC_CLOCK_LIMIT			0xa0
+#define MC_STAT_EMC_CLOCKS			0xa4
+#define MC_STAT_EMC_CONTROL_0			0xa8
+#define MC_STAT_EMC_CONTROL_1			0xac
+#define MC_STAT_EMC_COUNT_0			0xb8
+#define MC_STAT_EMC_COUNT_1			0xbc
+
+#define MC_STAT_CONTROL_CLIENT_ID		GENMASK(13,  8)
+#define MC_STAT_CONTROL_EVENT			GENMASK(23, 16)
+#define MC_STAT_CONTROL_PRI_EVENT		GENMASK(25, 24)
+#define MC_STAT_CONTROL_FILTER_CLIENT_ENABLE	GENMASK(26, 26)
+#define MC_STAT_CONTROL_FILTER_PRI		GENMASK(29, 28)
+
+#define MC_STAT_CONTROL_PRI_EVENT_HP		0
+#define MC_STAT_CONTROL_PRI_EVENT_TM		1
+#define MC_STAT_CONTROL_PRI_EVENT_BW		2
+
+#define MC_STAT_CONTROL_FILTER_PRI_DISABLE	0
+#define MC_STAT_CONTROL_FILTER_PRI_NO		1
+#define MC_STAT_CONTROL_FILTER_PRI_YES		2
+
+#define MC_STAT_CONTROL_EVENT_QUALIFIED		0
+#define MC_STAT_CONTROL_EVENT_ANY_READ		1
+#define MC_STAT_CONTROL_EVENT_ANY_WRITE		2
+#define MC_STAT_CONTROL_EVENT_RD_WR_CHANGE	3
+#define MC_STAT_CONTROL_EVENT_SUCCESSIVE	4
+#define MC_STAT_CONTROL_EVENT_ARB_BANK_AA	5
+#define MC_STAT_CONTROL_EVENT_ARB_BANK_BB	6
+#define MC_STAT_CONTROL_EVENT_PAGE_MISS		7
+#define MC_STAT_CONTROL_EVENT_AUTO_PRECHARGE	8
+
+#define EMC_GATHER_RST				(0 << 8)
+#define EMC_GATHER_CLEAR			(1 << 8)
+#define EMC_GATHER_DISABLE			(2 << 8)
+#define EMC_GATHER_ENABLE			(3 << 8)
+
+#define MC_STAT_SAMPLE_TIME_USEC		16000
+
+/* we store collected statistics as a fixed point values */
+#define MC_FX_FRAC_SCALE			100
+
+struct tegra20_mc_stat_gather {
+	unsigned int pri_filter;
+	unsigned int pri_event;
+	unsigned int result;
+	unsigned int client;
+	unsigned int event;
+	bool client_enb;
+};
+
+struct tegra20_mc_stat {
+	struct tegra20_mc_stat_gather gather0;
+	struct tegra20_mc_stat_gather gather1;
+	unsigned int sample_time_usec;
+	const struct tegra_mc *mc;
+};
+
+struct tegra20_mc_client_stat {
+	unsigned int events;
+	unsigned int arb_high_prio;
+	unsigned int arb_timeout;
+	unsigned int arb_bandwidth;
+	unsigned int rd_wr_change;
+	unsigned int successive;
+	unsigned int page_miss;
+	unsigned int auto_precharge;
+	unsigned int arb_bank_aa;
+	unsigned int arb_bank_bb;
+};
+
 static const struct tegra_mc_client tegra20_mc_clients[] = {
 	{
 		.id = 0x00,
@@ -356,6 +429,258 @@ static const struct tegra_mc_icc_ops tegra20_mc_icc_ops = {
 	.set = tegra20_mc_icc_set,
 };
 
+static u32 tegra20_mc_stat_gather_control(const struct tegra20_mc_stat_gather *g)
+{
+	u32 control;
+
+	control  = FIELD_PREP(MC_STAT_CONTROL_EVENT, g->event);
+	control |= FIELD_PREP(MC_STAT_CONTROL_CLIENT_ID, g->client);
+	control |= FIELD_PREP(MC_STAT_CONTROL_PRI_EVENT, g->pri_event);
+	control |= FIELD_PREP(MC_STAT_CONTROL_FILTER_PRI, g->pri_filter);
+	control |= FIELD_PREP(MC_STAT_CONTROL_FILTER_CLIENT_ENABLE, g->client_enb);
+
+	return control;
+}
+
+static void tegra20_mc_stat_gather(struct tegra20_mc_stat *stat)
+{
+	u32 clocks, count0, count1, control_0, control_1;
+	const struct tegra_mc *mc = stat->mc;
+
+	control_0 = tegra20_mc_stat_gather_control(&stat->gather0);
+	control_1 = tegra20_mc_stat_gather_control(&stat->gather1);
+
+	/*
+	 * Reset statistic gathers state, select bandwidth mode for the
+	 * statistics collection mode and set clocks counter saturation
+	 * limit to maximum.
+	 */
+	mc_writel(mc, 0x00000000, MC_STAT_CONTROL);
+	mc_writel(mc,  control_0, MC_STAT_EMC_CONTROL_0);
+	mc_writel(mc,  control_1, MC_STAT_EMC_CONTROL_1);
+	mc_writel(mc, 0xffffffff, MC_STAT_EMC_CLOCK_LIMIT);
+
+	mc_writel(mc, EMC_GATHER_ENABLE, MC_STAT_CONTROL);
+	fsleep(stat->sample_time_usec);
+	mc_writel(mc, EMC_GATHER_DISABLE, MC_STAT_CONTROL);
+
+	count0 = mc_readl(mc, MC_STAT_EMC_COUNT_0);
+	count1 = mc_readl(mc, MC_STAT_EMC_COUNT_1);
+	clocks = mc_readl(mc, MC_STAT_EMC_CLOCKS);
+	clocks = max(clocks / 100 / MC_FX_FRAC_SCALE, 1u);
+
+	stat->gather0.result = DIV_ROUND_UP(count0, clocks);
+	stat->gather1.result = DIV_ROUND_UP(count1, clocks);
+}
+
+static void tegra20_mc_stat_events(const struct tegra_mc *mc,
+				   const struct tegra_mc_client *client0,
+				   const struct tegra_mc_client *client1,
+				   unsigned int pri_filter,
+				   unsigned int pri_event,
+				   unsigned int event,
+				   unsigned int *result0,
+				   unsigned int *result1)
+{
+	struct tegra20_mc_stat stat = {};
+
+	stat.gather0.client = client0 ? client0->id : 0;
+	stat.gather0.pri_filter = pri_filter;
+	stat.gather0.client_enb = !!client0;
+	stat.gather0.pri_event = pri_event;
+	stat.gather0.event = event;
+
+	stat.gather1.client = client1 ? client1->id : 0;
+	stat.gather1.pri_filter = pri_filter;
+	stat.gather1.client_enb = !!client1;
+	stat.gather1.pri_event = pri_event;
+	stat.gather1.event = event;
+
+	stat.sample_time_usec = MC_STAT_SAMPLE_TIME_USEC;
+	stat.mc = mc;
+
+	tegra20_mc_stat_gather(&stat);
+
+	*result0 = stat.gather0.result;
+	*result1 = stat.gather1.result;
+}
+
+static void tegra20_mc_collect_stats(const struct tegra_mc *mc,
+				     struct tegra20_mc_client_stat *stats)
+{
+	const struct tegra_mc_client *client0, *client1;
+	unsigned int i;
+
+	/* collect memory controller utilization percent for each client */
+	for (i = 0; i < mc->soc->num_clients; i += 2) {
+		client0 = &mc->soc->clients[i];
+		client1 = &mc->soc->clients[i + 1];
+
+		if (i + 1 == mc->soc->num_clients)
+			client1 = NULL;
+
+		tegra20_mc_stat_events(mc, client0, client1,
+				       MC_STAT_CONTROL_FILTER_PRI_DISABLE,
+				       MC_STAT_CONTROL_PRI_EVENT_HP,
+				       MC_STAT_CONTROL_EVENT_QUALIFIED,
+				       &stats[i + 0].events,
+				       &stats[i + 1].events);
+	}
+
+	/* collect more info from active clients */
+	for (i = 0; i < mc->soc->num_clients; i++) {
+		unsigned int clienta, clientb = mc->soc->num_clients;
+
+		for (client0 = NULL; i < mc->soc->num_clients; i++) {
+			if (stats[i].events) {
+				client0 = &mc->soc->clients[i];
+				clienta = i++;
+				break;
+			}
+		}
+
+		for (client1 = NULL; i < mc->soc->num_clients; i++) {
+			if (stats[i].events) {
+				client1 = &mc->soc->clients[i];
+				clientb = i;
+				break;
+			}
+		}
+
+		if (!client0 && !client1)
+			break;
+
+		tegra20_mc_stat_events(mc, client0, client1,
+				       MC_STAT_CONTROL_FILTER_PRI_YES,
+				       MC_STAT_CONTROL_PRI_EVENT_HP,
+				       MC_STAT_CONTROL_EVENT_QUALIFIED,
+				       &stats[clienta].arb_high_prio,
+				       &stats[clientb].arb_high_prio);
+
+		tegra20_mc_stat_events(mc, client0, client1,
+				       MC_STAT_CONTROL_FILTER_PRI_YES,
+				       MC_STAT_CONTROL_PRI_EVENT_TM,
+				       MC_STAT_CONTROL_EVENT_QUALIFIED,
+				       &stats[clienta].arb_timeout,
+				       &stats[clientb].arb_timeout);
+
+		tegra20_mc_stat_events(mc, client0, client1,
+				       MC_STAT_CONTROL_FILTER_PRI_YES,
+				       MC_STAT_CONTROL_PRI_EVENT_BW,
+				       MC_STAT_CONTROL_EVENT_QUALIFIED,
+				       &stats[clienta].arb_bandwidth,
+				       &stats[clientb].arb_bandwidth);
+
+		tegra20_mc_stat_events(mc, client0, client1,
+				       MC_STAT_CONTROL_FILTER_PRI_DISABLE,
+				       MC_STAT_CONTROL_PRI_EVENT_HP,
+				       MC_STAT_CONTROL_EVENT_RD_WR_CHANGE,
+				       &stats[clienta].rd_wr_change,
+				       &stats[clientb].rd_wr_change);
+
+		tegra20_mc_stat_events(mc, client0, client1,
+				       MC_STAT_CONTROL_FILTER_PRI_DISABLE,
+				       MC_STAT_CONTROL_PRI_EVENT_HP,
+				       MC_STAT_CONTROL_EVENT_SUCCESSIVE,
+				       &stats[clienta].successive,
+				       &stats[clientb].successive);
+
+		tegra20_mc_stat_events(mc, client0, client1,
+				       MC_STAT_CONTROL_FILTER_PRI_DISABLE,
+				       MC_STAT_CONTROL_PRI_EVENT_HP,
+				       MC_STAT_CONTROL_EVENT_PAGE_MISS,
+				       &stats[clienta].page_miss,
+				       &stats[clientb].page_miss);
+	}
+}
+
+static void tegra20_mc_printf_percents(struct seq_file *s,
+				       const char *fmt,
+				       unsigned int percents_fx)
+{
+	char percents_str[8];
+
+	snprintf(percents_str, ARRAY_SIZE(percents_str), "%3u.%02u%%",
+		 percents_fx / MC_FX_FRAC_SCALE, percents_fx % MC_FX_FRAC_SCALE);
+
+	seq_printf(s, fmt, percents_str);
+}
+
+static int tegra20_mc_stats_show(struct seq_file *s, void *unused)
+{
+	const struct tegra_mc *mc = dev_get_drvdata(s->private);
+	struct tegra20_mc_client_stat *stats;
+	unsigned int i;
+
+	stats = kcalloc(mc->soc->num_clients + 1, sizeof(*stats), GFP_KERNEL);
+	if (!stats)
+		return -ENOMEM;
+
+	tegra20_mc_collect_stats(mc, stats);
+
+	seq_puts(s, "Memory client   Events   Timeout   High priority   Bandwidth ARB   RW change   Successive   Page miss\n");
+	seq_puts(s, "-----------------------------------------------------------------------------------------------------\n");
+
+	for (i = 0; i < mc->soc->num_clients; i++) {
+		seq_printf(s, "%-14s  ", mc->soc->clients[i].name);
+
+		/* An event is generated when client performs R/W request. */
+		tegra20_mc_printf_percents(s,  "%-9s", stats[i].events);
+
+		/*
+		 * An event is generated based on the timeout (TM) signal
+		 * accompanying a request for arbitration.
+		 */
+		tegra20_mc_printf_percents(s, "%-10s", stats[i].arb_timeout);
+
+		/*
+		 * An event is generated based on the high-priority (HP) signal
+		 * accompanying a request for arbitration.
+		 */
+		tegra20_mc_printf_percents(s, "%-16s", stats[i].arb_high_prio);
+
+		/*
+		 * An event is generated based on the bandwidth (BW) signal
+		 * accompanying a request for arbitration.
+		 */
+		tegra20_mc_printf_percents(s, "%-16s", stats[i].arb_bandwidth);
+
+		/*
+		 * An event is generated when the memory controller switches
+		 * between making a read request to making a write request.
+		 */
+		tegra20_mc_printf_percents(s, "%-12s", stats[i].rd_wr_change);
+
+		/*
+		 * An even generated when the chosen client has wins arbitration
+		 * when it was also the winner at the previous request.  If a
+		 * client makes N requests in a row that are honored, SUCCESSIVE
+		 * will be counted (N-1) times.  Large values for this event
+		 * imply that if we were patient enough, all of those requests
+		 * could have been coalesced.
+		 */
+		tegra20_mc_printf_percents(s, "%-13s", stats[i].successive);
+
+		/*
+		 * An event is generated when the memory controller detects a
+		 * page miss for the current request.
+		 */
+		tegra20_mc_printf_percents(s, "%-12s\n", stats[i].page_miss);
+	}
+
+	kfree(stats);
+
+	return 0;
+}
+
+static int tegra20_mc_init(struct tegra_mc *mc)
+{
+	debugfs_create_devm_seqfile(mc->dev, "stats", mc->debugfs.root,
+				    tegra20_mc_stats_show);
+
+	return 0;
+}
+
 const struct tegra_mc_soc tegra20_mc_soc = {
 	.clients = tegra20_mc_clients,
 	.num_clients = ARRAY_SIZE(tegra20_mc_clients),
@@ -367,4 +692,5 @@ const struct tegra_mc_soc tegra20_mc_soc = {
 	.resets = tegra20_mc_resets,
 	.num_resets = ARRAY_SIZE(tegra20_mc_resets),
 	.icc_ops = &tegra20_mc_icc_ops,
+	.init = tegra20_mc_init,
 };

include/soc/tegra/mc.h

@@ -7,6 +7,7 @@
 #define __SOC_TEGRA_MC_H__
 
 #include <linux/bits.h>
+#include <linux/debugfs.h>
 #include <linux/err.h>
 #include <linux/interconnect-provider.h>
 #include <linux/reset-controller.h>
@@ -175,6 +176,8 @@ struct tegra_mc_soc {
 	unsigned int num_resets;
 
 	const struct tegra_mc_icc_ops *icc_ops;
+
+	int (*init)(struct tegra_mc *mc);
 };
 
 struct tegra_mc {
@@ -196,6 +199,10 @@ struct tegra_mc {
 	struct icc_provider provider;
 
 	spinlock_t lock;
+
+	struct {
+		struct dentry *root;
+	} debugfs;
 };
 
 int tegra_mc_write_emem_configuration(struct tegra_mc *mc, unsigned long rate);