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);

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);