memory: tegra: Add EMC scaling support code for Tegra210

This is the initial patch for Tegra210 EMC frequency scaling. It has the
code to program various aspects of the EMC that are standardized, but it
does not yet include the specific programming sequence needed for clock
scaling.

The driver is designed to support LPDDR4 SDRAM. Devices that use LPDDR4
need to perform training of the RAM before it can be used. Firmware will
perform this training during early boot and pass a table of supported
frequencies to the kernel via device tree.

For the frequencies above 800 MHz, periodic retraining is needed to
compensate for changes in timing. This periodic training will have to be
performed until the frequency drops back to or below 800 MHz.

This driver provides helpers used during this runtime retraining that
will be used by the sequence specific code in a follow-up patch.

Based on work by Peter De Schrijver <pdeschrijver@nvidia.com>.

Signed-off-by: Joseph Lo <josephl@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/drivers/memory/tegra/tegra210-emc-table.c b/drivers/memory/tegra/tegra210-emc-table.c
new file mode 100644
index 000000000000..a5ab6e9e743a
--- /dev/null
+++ b/drivers/memory/tegra/tegra210-emc-table.c
@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2020, NVIDIA CORPORATION.  All rights reserved.
+ */
+
+#include <linux/of_reserved_mem.h>
+
+#include "tegra210-emc.h"
+
+#define TEGRA_EMC_MAX_FREQS		16
+
+static int tegra210_emc_table_device_init(struct reserved_mem *rmem,
+					  struct device *dev)
+{
+	struct tegra210_emc *emc = dev_get_drvdata(dev);
+	unsigned int i;
+
+	emc->timings = memremap(rmem->base, rmem->size, MEMREMAP_WB);
+	if (!emc->timings) {
+		dev_err(dev, "failed to map EMC table\n");
+		return -ENOMEM;
+	}
+
+	emc->num_timings = 0;
+
+	for (i = 0; i < TEGRA_EMC_MAX_FREQS; i++) {
+		if (emc->timings[i].revision == 0)
+			break;
+
+		emc->num_timings++;
+	}
+
+	return 0;
+}
+
+static void tegra210_emc_table_device_release(struct reserved_mem *rmem,
+					      struct device *dev)
+{
+	struct tegra210_emc *emc = dev_get_drvdata(dev);
+
+	memunmap(emc->timings);
+}
+
+static const struct reserved_mem_ops tegra210_emc_table_ops = {
+	.device_init = tegra210_emc_table_device_init,
+	.device_release = tegra210_emc_table_device_release,
+};
+
+static int tegra210_emc_table_init(struct reserved_mem *rmem)
+{
+	pr_debug("Tegra210 EMC table at %pa, size %lu bytes\n", &rmem->base,
+		 (unsigned long)rmem->size);
+
+	rmem->ops = &tegra210_emc_table_ops;
+
+	return 0;
+}
+RESERVEDMEM_OF_DECLARE(tegra210_emc_table, "nvidia,tegra210-emc-table",
+		       tegra210_emc_table_init);