[PATCH 0/2] Add support for PL172 memory-controller

[PATCH 0/2] Add support for PL172 memory-controller

[Joachim Eastwood]

This patch set adds support for setting up static memory devices on
a ARM PrimeCell MultiPort Memory Controller (PL172) from DT. Dynamic
memory (SDRAM) is not supported in this patch set.

DT bindings for PL172 is based on the bindings for the TI AEMIF
memory controller. PL172 can be found on a number of NXP devices
like the LPC18xx family.

Tested on Embedded Artists' LPC4357 Developer's Kit with NOR Flash
(SST39VF320) and 74LCV16374 (gpio-74x164) on MPMC.

Joachim Eastwood (2):
  memory: add ARM PL172 MultiPort Memory Controller driver
  doc: dt: add documentation for pl172 memory bindings

 .../bindings/memory-controllers/arm,pl172.txt      | 125 +++++++++
 drivers/memory/Kconfig                             |   8 +
 drivers/memory/Makefile                            |   1 +
 drivers/memory/pl172.c                             | 302 +++++++++++++++++++++
 4 files changed, 436 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/memory-controllers/arm,pl172.txt
 create mode 100644 drivers/memory/pl172.c

-- 
1.8.0

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[PATCH 1/2] memory: add ARM PL172 MultiPort Memory Controller driver

[Joachim Eastwood]

Signed-off-by: Joachim Eastwood <manabian-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 drivers/memory/Kconfig  |   8 ++
 drivers/memory/Makefile |   1 +
 drivers/memory/pl172.c  | 302 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 311 insertions(+)
 create mode 100644 drivers/memory/pl172.c

diff --git a/drivers/memory/Kconfig b/drivers/memory/Kconfig
index 868036f70f8f..f69a8842ec69 100644
--- a/drivers/memory/Kconfig
+++ b/drivers/memory/Kconfig
@@ -7,6 +7,14 @@ menuconfig MEMORY
 
 if MEMORY
 
+config ARM_PL172_MPMC
+	tristate "ARM PL172 MPMC driver"
+	depends on ARM_AMBA && OF
+	help
+	  This selects the ARM PrimeCell PL172 MultiPort Memory Controller.
+	  If you have an embedded system with an AMBA bus and a PL172
+	  controller, say Y or M here.
+
 config ATMEL_SDRAMC
 	bool "Atmel (Multi-port DDR-)SDRAM Controller"
 	default y
diff --git a/drivers/memory/Makefile b/drivers/memory/Makefile
index b670441e3cdf..1c46af501610 100644
--- a/drivers/memory/Makefile
+++ b/drivers/memory/Makefile
@@ -5,6 +5,7 @@
 ifeq ($(CONFIG_DDR),y)
 obj-$(CONFIG_OF)		+= of_memory.o
 endif
+obj-$(CONFIG_ARM_PL172_MPMC)	+= pl172.o
 obj-$(CONFIG_ATMEL_SDRAMC)	+= atmel-sdramc.o
 obj-$(CONFIG_TI_AEMIF)		+= ti-aemif.o
 obj-$(CONFIG_TI_EMIF)		+= emif.o
diff --git a/drivers/memory/pl172.c b/drivers/memory/pl172.c
new file mode 100644
index 000000000000..552f92da9369
--- /dev/null
+++ b/drivers/memory/pl172.c
@@ -0,0 +1,302 @@
+/*
+ * Memory controller driver for ARM PrimeCell PL172
+ * PrimeCell MultiPort Memory Controller (PL172)
+ *
+ * Copyright (C) 2015 Joachim Eastwood <manabian-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
+ *
+ * Based on:
+ * TI AEMIF driver, Copyright (C) 2010 - 2013 Texas Instruments Inc.
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/amba/bus.h>
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/time.h>
+
+#define MPMC_STATIC_CFG(n)		(0x200 + 0x20 * n)
+#define  MPMC_STATIC_CFG_MW_8BIT	0x0
+#define  MPMC_STATIC_CFG_MW_16BIT	0x1
+#define  MPMC_STATIC_CFG_MW_32BIT	0x2
+#define  MPMC_STATIC_CFG_PM		BIT(3)
+#define  MPMC_STATIC_CFG_PC		BIT(6)
+#define  MPMC_STATIC_CFG_PB		BIT(7)
+#define  MPMC_STATIC_CFG_EW		BIT(8)
+#define  MPMC_STATIC_CFG_B		BIT(19)
+#define  MPMC_STATIC_CFG_P		BIT(20)
+#define MPMC_STATIC_WAIT_WEN(n)		(0x204 + 0x20 * n)
+#define  MPMC_STATIC_WAIT_WEN_MAX	0x0f
+#define MPMC_STATIC_WAIT_OEN(n)		(0x208 + 0x20 * n)
+#define  MPMC_STATIC_WAIT_OEN_MAX	0x0f
+#define MPMC_STATIC_WAIT_RD(n)		(0x20c + 0x20 * n)
+#define  MPMC_STATIC_WAIT_RD_MAX	0x1f
+#define MPMC_STATIC_WAIT_PAGE(n)	(0x210 + 0x20 * n)
+#define  MPMC_STATIC_WAIT_PAGE_MAX	0x1f
+#define MPMC_STATIC_WAIT_WR(n)		(0x214 + 0x20 * n)
+#define  MPMC_STATIC_WAIT_WR_MAX	0x1f
+#define MPMC_STATIC_WAIT_TURN(n)	(0x218 + 0x20 * n)
+#define  MPMC_STATIC_WAIT_TURN_MAX	0x0f
+
+/* Maximum number of static chip selects */
+#define PL172_MAX_CS		4
+
+struct pl172_data {
+	void __iomem *base;
+	unsigned long rate;
+	struct clk *clk;
+};
+
+static int pl172_timing_prop(struct amba_device *adev,
+			     const struct device_node *np, const char *name,
+			     u32 reg_offset, u32 max, int start)
+{
+	struct pl172_data *pl172 = amba_get_drvdata(adev);
+	int cycles;
+	u32 val;
+
+	if (!of_property_read_u32(np, name, &val)) {
+		cycles = DIV_ROUND_UP(val * pl172->rate, NSEC_PER_MSEC) - start;
+		if (cycles < 0) {
+			cycles = 0;
+		} else if (cycles > max) {
+			dev_err(&adev->dev, "%s timing too tight\n", name);
+			return -EINVAL;
+		}
+
+		writel(cycles, pl172->base + reg_offset);
+	}
+
+	dev_dbg(&adev->dev, "%s: %u cycle(s)\n", name, start +
+				readl(pl172->base + reg_offset));
+
+	return 0;
+}
+
+static int pl172_setup_static(struct amba_device *adev,
+			      struct device_node *np, u32 cs)
+{
+	struct pl172_data *pl172 = amba_get_drvdata(adev);
+	u32 cfg;
+	int ret;
+
+	/* MPMC static memory configuration */
+	if (!of_property_read_u32(np, "mpmc,memory-width", &cfg)) {
+		if (cfg == 8) {
+			cfg = MPMC_STATIC_CFG_MW_8BIT;
+		} else if (cfg == 16) {
+			cfg = MPMC_STATIC_CFG_MW_16BIT;
+		} else if (cfg == 32) {
+			cfg = MPMC_STATIC_CFG_MW_32BIT;
+		} else {
+			dev_err(&adev->dev, "invalid memory width cs%u\n", cs);
+			return -EINVAL;
+		}
+	} else {
+		dev_err(&adev->dev, "memory-width property required\n");
+		return -EINVAL;
+	}
+
+	if (of_property_read_bool(np, "mpmc,async-page-mode"))
+		cfg |= MPMC_STATIC_CFG_PM;
+
+	if (of_property_read_bool(np, "mpmc,cs-active-high"))
+		cfg |= MPMC_STATIC_CFG_PC;
+
+	if (of_property_read_bool(np, "mpmc,byte-lane-low"))
+		cfg |= MPMC_STATIC_CFG_PB;
+
+	if (of_property_read_bool(np, "mpmc,extended-wait"))
+		cfg |= MPMC_STATIC_CFG_EW;
+
+	if (of_property_read_bool(np, "mpmc,buffer-enable"))
+		cfg |= MPMC_STATIC_CFG_B;
+
+	if (of_property_read_bool(np, "mpmc,write-protect"))
+		cfg |= MPMC_STATIC_CFG_P;
+
+	writel(cfg, pl172->base + MPMC_STATIC_CFG(cs));
+	dev_dbg(&adev->dev, "mpmc static config cs%u: 0x%08x\n", cs, cfg);
+
+	/* MPMC static memory timing */
+	ret = pl172_timing_prop(adev, np, "mpmc,write-enable-delay",
+				MPMC_STATIC_WAIT_WEN(cs),
+				MPMC_STATIC_WAIT_WEN_MAX, 1);
+	if (ret)
+		goto fail;
+
+	ret = pl172_timing_prop(adev, np, "mpmc,output-enable-delay",
+				MPMC_STATIC_WAIT_OEN(cs),
+				MPMC_STATIC_WAIT_OEN_MAX, 0);
+	if (ret)
+		goto fail;
+
+	ret = pl172_timing_prop(adev, np, "mpmc,read-access-delay",
+				MPMC_STATIC_WAIT_RD(cs),
+				MPMC_STATIC_WAIT_RD_MAX, 1);
+	if (ret)
+		goto fail;
+
+	ret = pl172_timing_prop(adev, np, "mpmc,page-mode-read-delay",
+				MPMC_STATIC_WAIT_PAGE(cs),
+				MPMC_STATIC_WAIT_PAGE_MAX, 1);
+	if (ret)
+		goto fail;
+
+	ret = pl172_timing_prop(adev, np, "mpmc,write-access-delay",
+				MPMC_STATIC_WAIT_WR(cs),
+				MPMC_STATIC_WAIT_WR_MAX, 2);
+	if (ret)
+		goto fail;
+
+	ret = pl172_timing_prop(adev, np, "mpmc,turn-round-delay",
+				MPMC_STATIC_WAIT_TURN(cs),
+				MPMC_STATIC_WAIT_TURN_MAX, 1);
+	if (ret)
+		goto fail;
+
+	return 0;
+fail:
+	dev_err(&adev->dev, "failed to configure cs%u\n", cs);
+	return ret;
+}
+
+static int pl172_parse_cs_config(struct amba_device *adev,
+				 struct device_node *np)
+{
+	u32 cs;
+
+	if (!of_property_read_u32(np, "mpmc,cs", &cs)) {
+		if (cs >= PL172_MAX_CS) {
+			dev_err(&adev->dev, "cs%u invalid\n", cs);
+			return -EINVAL;
+		}
+
+		return pl172_setup_static(adev, np, cs);
+	}
+
+	dev_err(&adev->dev, "cs property required\n");
+
+	return -EINVAL;
+}
+
+static const char * const pl172_revisions[] = {"r1", "r2", "r2p3", "r2p4"};
+
+static int pl172_probe(struct amba_device *adev, const struct amba_id *id)
+{
+	struct device_node *child_np, *np = adev->dev.of_node;
+	struct device *dev = &adev->dev;
+	static const char *rev = "?";
+	struct pl172_data *pl172;
+	int ret;
+
+	if (amba_part(adev) == 0x172) {
+		if (amba_rev(adev) < ARRAY_SIZE(pl172_revisions))
+			rev = pl172_revisions[amba_rev(adev)];
+	}
+
+	dev_info(dev, "ARM PL%x revision %s\n", amba_part(adev), rev);
+
+	pl172 = devm_kzalloc(dev, sizeof(*pl172), GFP_KERNEL);
+	if (!pl172)
+		return -ENOMEM;
+
+	pl172->clk = devm_clk_get(dev, "mpmcclk");
+	if (IS_ERR(pl172->clk)) {
+		dev_err(dev, "no mpmcclk provided clock\n");
+		return PTR_ERR(pl172->clk);
+	}
+
+	ret = clk_prepare_enable(pl172->clk);
+	if (ret) {
+		dev_err(dev, "unable to mpmcclk enable clock\n");
+		return ret;
+	}
+
+	pl172->rate = clk_get_rate(pl172->clk) / MSEC_PER_SEC;
+	if (!pl172->rate) {
+		dev_err(dev, "unable to get mpmcclk clock rate\n");
+		ret = -EINVAL;
+		goto err_clk_enable;
+	}
+
+	ret = amba_request_regions(adev, NULL);
+	if (ret) {
+		dev_err(dev, "unable to request AMBA regions\n");
+		goto err_clk_enable;
+	}
+
+	pl172->base = devm_ioremap(dev, adev->res.start,
+				   resource_size(&adev->res));
+	if (!pl172->base) {
+		dev_err(dev, "ioremap failed\n");
+		ret = -ENOMEM;
+		goto err_no_ioremap;
+	}
+
+	amba_set_drvdata(adev, pl172);
+
+	/*
+	 * Loop through each child node, which represent a chip select, and
+	 * configure parameters and timing. If successful; populate devices
+	 * under that node.
+	 */
+	for_each_available_child_of_node(np, child_np) {
+		ret = pl172_parse_cs_config(adev, child_np);
+		if (ret)
+			continue;
+
+		of_platform_populate(child_np, of_default_bus_match_table,
+				     NULL, dev);
+	}
+
+	return 0;
+
+err_no_ioremap:
+	amba_release_regions(adev);
+err_clk_enable:
+	clk_disable_unprepare(pl172->clk);
+	return ret;
+}
+
+static int pl172_remove(struct amba_device *adev)
+{
+	struct pl172_data *pl172 = amba_get_drvdata(adev);
+
+	clk_disable_unprepare(pl172->clk);
+	amba_release_regions(adev);
+
+	return 0;
+}
+
+static struct amba_id pl172_ids[] = {
+	{
+		.id	= 0x07341172,
+		.mask	= 0xffffffff,
+	},
+	{ 0, 0 },
+};
+MODULE_DEVICE_TABLE(amba, pl172_ids);
+
+static struct amba_driver pl172_driver = {
+	.drv = {
+		.name	= "memory-pl172",
+	},
+	.probe		= pl172_probe,
+	.remove		= pl172_remove,
+	.id_table	= pl172_ids,
+};
+module_amba_driver(pl172_driver);
+
+MODULE_AUTHOR("Joachim Eastwood <manabian-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>");
+MODULE_DESCRIPTION("PL172 Memory Controller Driver");
+MODULE_LICENSE("GPL v2");
-- 
1.8.0

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[PATCH 2/2] doc: dt: add documentation for pl172 memory bindings

[Joachim Eastwood]

Signed-off-by: Joachim Eastwood <manabian-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 .../bindings/memory-controllers/arm,pl172.txt      | 125 +++++++++++++++++++++
 1 file changed, 125 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/memory-controllers/arm,pl172.txt

diff --git a/Documentation/devicetree/bindings/memory-controllers/arm,pl172.txt b/Documentation/devicetree/bindings/memory-controllers/arm,pl172.txt
new file mode 100644
index 000000000000..e6df32f9986d
--- /dev/null
+++ b/Documentation/devicetree/bindings/memory-controllers/arm,pl172.txt
@@ -0,0 +1,125 @@
+* Device tree bindings for ARM PL172 MultiPort Memory Controller
+
+Required properties:
+
+- compatible:		"arm,pl172", "arm,primecell"
+
+- reg:			Must contains offset/length value for controller.
+
+- #address-cells:	Must be 2. The partition number has to be encoded in the
+			first address cell and it may accept values 0..N-1
+			(N - total number of partitions). The second cell is the
+			offset into the partition.
+
+- #size-cells:		Must be set to 1.
+
+- ranges:		Must contain one or more chip select memory regions.
+
+- clocks:		Must contain references to controller clocks.
+
+- clock-names:		Must contain "mpmcclk" and "apb_pclk".
+
+- clock-ranges:		Empty property indicating that child nodes can inherit
+			named clocks. Required only if clock tree data present
+			in device tree.
+			See clock-bindings.txt
+
+Child chip-select (cs) nodes contain the memory devices nodes connected to
+such as NOR (e.g. cfi-flash) and NAND.
+
+Required child cs node properties:
+
+- #address-cells:	Must be 2.
+
+- #size-cells:		Must be 1.
+
+- ranges:		Empty property indicating that child nodes can inherit
+			memory layout.
+
+- clock-ranges:		Empty property indicating that child nodes can inherit
+			named clocks. Required only if clock tree data present
+			in device tree.
+
+- mpmc,cs:		Chip select number. Indicates to the pl0172 driver
+			which chipselect is used for accessing the memory.
+
+- mpmc,memory-width:	Width of the chip select memory. Must be equal to
+			either 8, 16 or 32.
+
+Optional child cs node config properties:
+
+- mpmc,async-page-mode:	Enable asynchronous page mode.
+
+- mpmc,cs-active-high:	Set chip select polarity to active high.
+
+- mpmc,byte-lane-low:	Set byte lane state to low.
+
+- mpmc,extended-wait:	Enable extended wait.
+
+- mpmc,buffer-enable:	Enable write buffer.
+
+- mpmc,write-protect:	Enable write protect.
+
+Optional child cs node timing properties:
+
+- mpmc,write-enable-delay:	Delay from chip select assertion to write
+				enable (WE signal) in nano seconds.
+
+- mpmc,output-enable-delay:	Delay from chip select assertion to output
+				enable (OE signal) in nano seconds.
+
+- mpmc,write-access-delay:	Delay from chip select assertion to write
+				access in nano seconds.
+
+- mpmc,read-access-delay:	Delay from chip select assertion to read
+				access in nano seconds.
+
+- mpmc,page-mode-read-delay:	Delay for asynchronous page mode sequential
+				accesses in nano seconds.
+
+- mpmc,turn-round-delay:	Delay between access to memory banks in nano
+				seconds.
+
+If any of the above timing parameters are absent, current parameter value will
+be taken from the corresponding HW reg.
+
+Example for pl172 with nor flash on chip select 0 shown below.
+
+emc: memory-controller@40005000 {
+	compatible = "arm,pl172", "arm,primecell";
+	reg = <0x40005000 0x1000>;
+	clocks = <&ccu1 CLK_CPU_EMCDIV>, <&ccu1 CLK_CPU_EMC>;
+	clock-names = "mpmcclk", "apb_pclk";
+	#address-cells = <2>;
+	#size-cells = <1>;
+	ranges = <0 0 0x1c000000 0x1000000
+		  1 0 0x1d000000 0x1000000
+		  2 0 0x1e000000 0x1000000
+		  3 0 0x1f000000 0x1000000>;
+
+	cs0 {
+		#address-cells = <2>;
+		#size-cells = <1>;
+		ranges;
+
+		mpmc,cs = <0>;
+		mpmc,memory-width = <16>;
+		mpmc,byte-lane-low;
+		mpmc,write-enable-delay = <0>;
+		mpmc,output-enable-delay = <0>;
+		mpmc,read-enable-delay = <70>;
+		mpmc,page-mode-read-delay = <70>;
+
+		flash@0,0 {
+			compatible = "sst,sst39vf320", "cfi-flash";
+			reg = <0 0 0x400000>;
+			bank-width = <2>;
+			#address-cells = <1>;
+			#size-cells = <1>;
+			partition@0 {
+				label = "data";
+				reg = <0 0x400000>;
+			};
+		};
+	};
+};
-- 
1.8.0

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Re: [PATCH 0/2] Add support for PL172 memory-controller

[Will Deacon]

Hi Joachim,

On Tue, Apr 28, 2015 at 06:24:37PM +0100, Joachim Eastwood wrote:
> This patch set adds support for setting up static memory devices on
> a ARM PrimeCell MultiPort Memory Controller (PL172) from DT. Dynamic
> memory (SDRAM) is not supported in this patch set.
> 
> DT bindings for PL172 is based on the bindings for the TI AEMIF
> memory controller. PL172 can be found on a number of NXP devices
> like the LPC18xx family.
> 
> Tested on Embedded Artists' LPC4357 Developer's Kit with NOR Flash
> (SST39VF320) and 74LCV16374 (gpio-74x164) on MPMC.

Please excuse my ignorance here, but is this memory controller used to
manage the memory in use by the kernel? If so, how is it safe to reconfigure
it dynamically at runtime? If not, then it might be worth describing
some typical use-cases in the binding documentation to motivate the
existence of this driver.

Cheers,

Will
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Re: [PATCH 0/2] Add support for PL172 memory-controller

[Joachim Eastwood]

On 28 April 2015 at 19:36, Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org> wrote:
> Hi Joachim,
>
> On Tue, Apr 28, 2015 at 06:24:37PM +0100, Joachim Eastwood wrote:
>> This patch set adds support for setting up static memory devices on
>> a ARM PrimeCell MultiPort Memory Controller (PL172) from DT. Dynamic
>> memory (SDRAM) is not supported in this patch set.
>>
>> DT bindings for PL172 is based on the bindings for the TI AEMIF
>> memory controller. PL172 can be found on a number of NXP devices
>> like the LPC18xx family.
>>
>> Tested on Embedded Artists' LPC4357 Developer's Kit with NOR Flash
>> (SST39VF320) and 74LCV16374 (gpio-74x164) on MPMC.
>
> Please excuse my ignorance here, but is this memory controller used to
> manage the memory in use by the kernel? If so, how is it safe to reconfigure
> it dynamically at runtime?

The driver is used to do a one-time configuration of static chip selects on
driver probe using the parameters specified in DT. The device nodes under the
MPMC node is only populated and then driver probed after the parameters has
been setup. This how most of drivers under drivers/memory operates.

>If not, then it might be worth describing
> some typical use-cases in the binding documentation to motivate the
> existence of this driver.

The typical use case is Flash memory (NAND and NOR) configuration and
timing setup but you could configure any kind of static memory devices on
the bus. But as described above this only happens at driver probe time.

Hope this answer your question.

regards,
Joachim Eastwood
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Re: [PATCH 2/2] doc: dt: add documentation for pl172 memory bindings

[Joachim Eastwood]

Hi DT maintainers,

Do you have any comments on the bindings below?

These bindings are based on bindings for "ti,davinci-aemif" found
under memory-controllers/ti-aemif.txt

regards,
Joachim Eastwood

On 28 April 2015 at 19:24, Joachim Eastwood <manabian-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> Signed-off-by: Joachim Eastwood <manabian-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
>  .../bindings/memory-controllers/arm,pl172.txt      | 125 +++++++++++++++++++++
>  1 file changed, 125 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/memory-controllers/arm,pl172.txt
>
> diff --git a/Documentation/devicetree/bindings/memory-controllers/arm,pl172.txt b/Documentation/devicetree/bindings/memory-controllers/arm,pl172.txt
> new file mode 100644
> index 000000000000..e6df32f9986d
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/memory-controllers/arm,pl172.txt
> @@ -0,0 +1,125 @@
> +* Device tree bindings for ARM PL172 MultiPort Memory Controller
> +
> +Required properties:
> +
> +- compatible:          "arm,pl172", "arm,primecell"
> +
> +- reg:                 Must contains offset/length value for controller.
> +
> +- #address-cells:      Must be 2. The partition number has to be encoded in the
> +                       first address cell and it may accept values 0..N-1
> +                       (N - total number of partitions). The second cell is the
> +                       offset into the partition.
> +
> +- #size-cells:         Must be set to 1.
> +
> +- ranges:              Must contain one or more chip select memory regions.
> +
> +- clocks:              Must contain references to controller clocks.
> +
> +- clock-names:         Must contain "mpmcclk" and "apb_pclk".
> +
> +- clock-ranges:                Empty property indicating that child nodes can inherit
> +                       named clocks. Required only if clock tree data present
> +                       in device tree.
> +                       See clock-bindings.txt
> +
> +Child chip-select (cs) nodes contain the memory devices nodes connected to
> +such as NOR (e.g. cfi-flash) and NAND.
> +
> +Required child cs node properties:
> +
> +- #address-cells:      Must be 2.
> +
> +- #size-cells:         Must be 1.
> +
> +- ranges:              Empty property indicating that child nodes can inherit
> +                       memory layout.
> +
> +- clock-ranges:                Empty property indicating that child nodes can inherit
> +                       named clocks. Required only if clock tree data present
> +                       in device tree.
> +
> +- mpmc,cs:             Chip select number. Indicates to the pl0172 driver
> +                       which chipselect is used for accessing the memory.
> +
> +- mpmc,memory-width:   Width of the chip select memory. Must be equal to
> +                       either 8, 16 or 32.
> +
> +Optional child cs node config properties:
> +
> +- mpmc,async-page-mode:        Enable asynchronous page mode.
> +
> +- mpmc,cs-active-high: Set chip select polarity to active high.
> +
> +- mpmc,byte-lane-low:  Set byte lane state to low.
> +
> +- mpmc,extended-wait:  Enable extended wait.
> +
> +- mpmc,buffer-enable:  Enable write buffer.
> +
> +- mpmc,write-protect:  Enable write protect.
> +
> +Optional child cs node timing properties:
> +
> +- mpmc,write-enable-delay:     Delay from chip select assertion to write
> +                               enable (WE signal) in nano seconds.
> +
> +- mpmc,output-enable-delay:    Delay from chip select assertion to output
> +                               enable (OE signal) in nano seconds.
> +
> +- mpmc,write-access-delay:     Delay from chip select assertion to write
> +                               access in nano seconds.
> +
> +- mpmc,read-access-delay:      Delay from chip select assertion to read
> +                               access in nano seconds.
> +
> +- mpmc,page-mode-read-delay:   Delay for asynchronous page mode sequential
> +                               accesses in nano seconds.
> +
> +- mpmc,turn-round-delay:       Delay between access to memory banks in nano
> +                               seconds.
> +
> +If any of the above timing parameters are absent, current parameter value will
> +be taken from the corresponding HW reg.
> +
> +Example for pl172 with nor flash on chip select 0 shown below.
> +
> +emc: memory-controller@40005000 {
> +       compatible = "arm,pl172", "arm,primecell";
> +       reg = <0x40005000 0x1000>;
> +       clocks = <&ccu1 CLK_CPU_EMCDIV>, <&ccu1 CLK_CPU_EMC>;
> +       clock-names = "mpmcclk", "apb_pclk";
> +       #address-cells = <2>;
> +       #size-cells = <1>;
> +       ranges = <0 0 0x1c000000 0x1000000
> +                 1 0 0x1d000000 0x1000000
> +                 2 0 0x1e000000 0x1000000
> +                 3 0 0x1f000000 0x1000000>;
> +
> +       cs0 {
> +               #address-cells = <2>;
> +               #size-cells = <1>;
> +               ranges;
> +
> +               mpmc,cs = <0>;
> +               mpmc,memory-width = <16>;
> +               mpmc,byte-lane-low;
> +               mpmc,write-enable-delay = <0>;
> +               mpmc,output-enable-delay = <0>;
> +               mpmc,read-enable-delay = <70>;
> +               mpmc,page-mode-read-delay = <70>;
> +
> +               flash@0,0 {
> +                       compatible = "sst,sst39vf320", "cfi-flash";
> +                       reg = <0 0 0x400000>;
> +                       bank-width = <2>;
> +                       #address-cells = <1>;
> +                       #size-cells = <1>;
> +                       partition@0 {
> +                               label = "data";
> +                               reg = <0 0x400000>;
> +                       };
> +               };
> +       };
> +};
> --
> 1.8.0
>
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