mtd: Add support for HyperBus memory devices

Cypress' HyperBus is Low Signal Count, High Performance Double Data Rate
Bus interface between a host system master and one or more slave
interfaces. HyperBus is used to connect microprocessor, microcontroller,
or ASIC devices with random access NOR flash memory (called HyperFlash)
or self refresh DRAM (called HyperRAM).

Its a 8-bit data bus (DQ[7:0]) with  Read-Write Data Strobe (RWDS)
signal and either Single-ended clock(3.0V parts) or Differential clock
(1.8V parts). It uses ChipSelect lines to select b/w multiple slaves.
At bus level, it follows a separate protocol described in HyperBus
specification[1].

HyperFlash follows CFI AMD/Fujitsu Extended Command Set (0x0002) similar
to that of existing parallel NORs. Since HyperBus is x8 DDR bus,
its equivalent to x16 parallel NOR flash with respect to bits per clock
cycle. But HyperBus operates at >166MHz frequencies.
HyperRAM provides direct random read/write access to flash memory
array.

But, HyperBus memory controllers seem to abstract implementation details
and expose a simple MMIO interface to access connected flash.

Add support for registering HyperFlash devices with MTD framework. MTD
maps framework along with CFI chip support framework are used to support
communicating with flash.

Framework is modelled along the lines of spi-nor framework. HyperBus
memory controller (HBMC) drivers calls hyperbus_register_device() to
register a single HyperFlash device. HyperFlash core parses MMIO access
information from DT, sets up the map_info struct, probes CFI flash and
registers it with MTD framework.

Some HBMC masters need calibration/training sequence[3] to be carried
out, in order for DLL inside the controller to lock, by reading a known
string/pattern. This is done by repeatedly reading CFI Query
Identification String. Calibration needs to be done before trying to detect
flash as part of CFI flash probe.

HyperRAM is not supported at the moment.

HyperBus specification can be found at[1]
HyperFlash datasheet can be found at[2]

[1] https://www.cypress.com/file/213356/download
[2] https://www.cypress.com/file/213346/download
[3] http://www.ti.com/lit/ug/spruid7b/spruid7b.pdf
    Table 12-5741. HyperFlash Access Sequence

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

3 files changed, 167 insertions, 0 deletions

diff --git a/drivers/mtd/hyperbus/Kconfig b/drivers/mtd/hyperbus/Kconfig
new file mode 100644
index 000000000000..98147e28caa0
--- /dev/null
+++ b/drivers/mtd/hyperbus/Kconfig
@@ -0,0 +1,11 @@
+menuconfig MTD_HYPERBUS
+	tristate "HyperBus support"
+	select MTD_CFI
+	select MTD_MAP_BANK_WIDTH_2
+	select MTD_CFI_AMDSTD
+	select MTD_COMPLEX_MAPPINGS
+	help
+	  This is the framework for the HyperBus which can be used by
+	  the HyperBus Controller driver to communicate with
+	  HyperFlash. See Cypress HyperBus specification for more
+	  details
diff --git a/drivers/mtd/hyperbus/Makefile b/drivers/mtd/hyperbus/Makefile
new file mode 100644
index 000000000000..ca61dedd730d
--- /dev/null
+++ b/drivers/mtd/hyperbus/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_MTD_HYPERBUS)	+= hyperbus-core.o
diff --git a/drivers/mtd/hyperbus/hyperbus-core.c b/drivers/mtd/hyperbus/hyperbus-core.c
new file mode 100644
index 000000000000..6af9ea34117d
--- /dev/null
+++ b/drivers/mtd/hyperbus/hyperbus-core.c
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Copyright (C) 2019 Texas Instruments Incorporated - http://www.ti.com/
+// Author: Vignesh Raghavendra <vigneshr@ti.com>
+
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mtd/hyperbus.h>
+#include <linux/mtd/map.h>
+#include <linux/mtd/mtd.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/types.h>
+
+static struct hyperbus_device *map_to_hbdev(struct map_info *map)
+{
+	return container_of(map, struct hyperbus_device, map);
+}
+
+static map_word hyperbus_read16(struct map_info *map, unsigned long addr)
+{
+	struct hyperbus_device *hbdev = map_to_hbdev(map);
+	struct hyperbus_ctlr *ctlr = hbdev->ctlr;
+	map_word read_data;
+
+	read_data.x[0] = ctlr->ops->read16(hbdev, addr);
+
+	return read_data;
+}
+
+static void hyperbus_write16(struct map_info *map, map_word d,
+			     unsigned long addr)
+{
+	struct hyperbus_device *hbdev = map_to_hbdev(map);
+	struct hyperbus_ctlr *ctlr = hbdev->ctlr;
+
+	ctlr->ops->write16(hbdev, addr, d.x[0]);
+}
+
+static void hyperbus_copy_from(struct map_info *map, void *to,
+			       unsigned long from, ssize_t len)
+{
+	struct hyperbus_device *hbdev = map_to_hbdev(map);
+	struct hyperbus_ctlr *ctlr = hbdev->ctlr;
+
+	ctlr->ops->copy_from(hbdev, to, from, len);
+}
+
+static void hyperbus_copy_to(struct map_info *map, unsigned long to,
+			     const void *from, ssize_t len)
+{
+	struct hyperbus_device *hbdev = map_to_hbdev(map);
+	struct hyperbus_ctlr *ctlr = hbdev->ctlr;
+
+	ctlr->ops->copy_to(hbdev, to, from, len);
+}
+
+int hyperbus_register_device(struct hyperbus_device *hbdev)
+{
+	const struct hyperbus_ops *ops;
+	struct hyperbus_ctlr *ctlr;
+	struct device_node *np;
+	struct map_info *map;
+	struct resource res;
+	struct device *dev;
+	int ret;
+
+	if (!hbdev || !hbdev->np || !hbdev->ctlr || !hbdev->ctlr->dev) {
+		pr_err("hyperbus: please fill all the necessary fields!\n");
+		return -EINVAL;
+	}
+
+	np = hbdev->np;
+	ctlr = hbdev->ctlr;
+	if (!of_device_is_compatible(np, "cypress,hyperflash"))
+		return -ENODEV;
+
+	hbdev->memtype = HYPERFLASH;
+
+	ret = of_address_to_resource(np, 0, &res);
+	if (ret)
+		return ret;
+
+	dev = ctlr->dev;
+	map = &hbdev->map;
+	map->size = resource_size(&res);
+	map->virt = devm_ioremap_resource(dev, &res);
+	if (IS_ERR(map->virt))
+		return PTR_ERR(map->virt);
+
+	map->name = dev_name(dev);
+	map->bankwidth = 2;
+	map->device_node = np;
+
+	simple_map_init(map);
+	ops = ctlr->ops;
+	if (ops) {
+		if (ops->read16)
+			map->read = hyperbus_read16;
+		if (ops->write16)
+			map->write = hyperbus_write16;
+		if (ops->copy_to)
+			map->copy_to = hyperbus_copy_to;
+		if (ops->copy_from)
+			map->copy_from = hyperbus_copy_from;
+
+		if (ops->calibrate && !ctlr->calibrated) {
+			ret = ops->calibrate(hbdev);
+			if (!ret) {
+				dev_err(dev, "Calibration failed\n");
+				return -ENODEV;
+			}
+			ctlr->calibrated = true;
+		}
+	}
+
+	hbdev->mtd = do_map_probe("cfi_probe", map);
+	if (!hbdev->mtd) {
+		dev_err(dev, "probing of hyperbus device failed\n");
+		return -ENODEV;
+	}
+
+	hbdev->mtd->dev.parent = dev;
+	mtd_set_of_node(hbdev->mtd, np);
+
+	ret = mtd_device_register(hbdev->mtd, NULL, 0);
+	if (ret) {
+		dev_err(dev, "failed to register mtd device\n");
+		map_destroy(hbdev->mtd);
+		return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hyperbus_register_device);
+
+int hyperbus_unregister_device(struct hyperbus_device *hbdev)
+{
+	int ret = 0;
+
+	if (hbdev && hbdev->mtd) {
+		ret = mtd_device_unregister(hbdev->mtd);
+		map_destroy(hbdev->mtd);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(hyperbus_unregister_device);
+
+MODULE_DESCRIPTION("HyperBus Framework");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Vignesh Raghavendra <vigneshr@ti.com>");