Re: [PATCHv4] mtd: gpio-nand: add device tree bindings

Jamie Iles
2011-08-11T09:00:22Z

On Wed, Aug 10, 2011 at 10:13:27AM -0500, Scott Wood wrote:
> On 08/09/2011 10:12 AM, Jamie Iles wrote:
> > +Optional properties:
> > +- bank-width : Width (in bytes) of the device. If not present, the width
> > + defaults to 8 bits.
>
> "in bytes" versus "defaults to 8 bits"...
>
> > +- chip-delay : chip dependent delay for transferring data from array to
> > + read registers (tR). If not present then a default of 0 is used.
>
> nand_set_defaults() will set this to 20 us if you pass in zero.
>
> > +- gpio-control-nand,io-sync-reg : A 64-bit physical address for a read
> > + location used to guard against bus reordering with regards to accesses to
> > + the GPIO's and the NAND flash data bus. If present, then after changing
> > + GPIO state, this register will be read to ensure that the accesses have
> > + completed.
>
> The driver does it before and after all cmd_ctrl byte writes, in
> addition to after changing the GPIO state.

Hmm, I haven't done a great job documenting this binding! Revised patch
below.

Thanks Scott!

8<----

From: Jamie Iles <jamie@jamieiles.com>
Subject: [PATCH] mtd: gpio-nand: add device tree bindings

Add device tree bindings so that the gpio-nand driver may be
instantiated from the device tree. This also allows the partitions
to be specified in the device tree.

v4:
- get io sync address from gpio-control-nand,io-sync-reg
property rather than a resource
- clarified a few details in the binding
v3:
- remove redundant cast and a couple of whitespace/naming
changes
v2:
- add CONFIG_OF guards for non-dt platforms
- compatible becomes gpio-control-nand
- clarify some binding details

Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Artem Bityutskiy <dedekind1@gmail.com>
Cc: Scott Wood <scottwood@freescale.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Jamie Iles <jamie@jamieiles.com>
---
.../devicetree/bindings/mtd/gpio-control-nand.txt | 44 ++++++
drivers/mtd/nand/gpio.c | 139 ++++++++++++++++++-
2 files changed, 175 insertions(+), 8 deletions(-)
create mode 100644 Documentation/devicetree/bindings/mtd/gpio-control-nand.txt

diff --git a/Documentation/devicetree/bindings/mtd/gpio-control-nand.txt b/Documentation/devicetree/bindings/mtd/gpio-control-nand.txt
new file mode 100644
index 0000000..719f4dc
--- /dev/null
+++ b/Documentation/devicetree/bindings/mtd/gpio-control-nand.txt
@@ -0,0 +1,44 @@
+GPIO assisted NAND flash
+
+The GPIO assisted NAND flash uses a memory mapped interface to
+read/write the NAND commands and data and GPIO pins for the control
+signals.
+
+Required properties:
+- compatible : "gpio-control-nand"
+- reg : should specify localbus chip select and size used for the chip. The
+ resource describes the data bus connected to the NAND flash and all accesses
+ are made in native endianness.
+- #address-cells, #size-cells : Must be present if the device has sub-nodes
+ representing partitions.
+- gpios : specifies the gpio pins to control the NAND device. nwp is an
+ optional gpio and may be set to 0 if not present.
+
+Optional properties:
+- bank-width : Width (in bytes) of the device. If not present, the width
+ defaults to 1 byte.
+- chip-delay : chip dependent delay for transferring data from array to
+ read registers (tR). If not present then a default of 20us is used.
+- gpio-control-nand,io-sync-reg : A 64-bit physical address for a read
+ location used to guard against bus reordering with regards to accesses to
+ the GPIO's and the NAND flash data bus. If present, then after changing
+ GPIO state and before and after command byte writes, this register will be
+ read to ensure that the GPIO accesses have completed.
+
+Examples:
+
+gpio-nand@1,0 {
+ compatible = "gpio-control-nand";
+ reg = <1 0x0000 0x2>;
+ #address-cells = <1>;
+ #size-cells = <1>;
+ gpios = <&banka 1 0 /* rdy */
+ &banka 2 0 /* nce */
+ &banka 3 0 /* ale */
+ &banka 4 0 /* cle */
+ 0 /* nwp */>;
+
+ partition@0 {
+ ...
+ };
+};
diff --git a/drivers/mtd/nand/gpio.c b/drivers/mtd/nand/gpio.c
index 2c2060b..89b819b 100644
--- a/drivers/mtd/nand/gpio.c
+++ b/drivers/mtd/nand/gpio.c
@@ -27,6 +27,9 @@
#include <linux/mtd/nand.h>
#include <linux/mtd/partitions.h>
#include <linux/mtd/nand-gpio.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_gpio.h>

struct gpiomtd {
void __iomem *io_sync;
@@ -171,6 +174,99 @@ static int gpio_nand_devready(struct mtd_info *mtd)
return gpio_get_value(gpiomtd->plat.gpio_rdy);
}

+#ifdef CONFIG_OF
+static const struct of_device_id gpio_nand_id_table[] = {
+ { .compatible = "gpio-control-nand" },
+ {}
+};
+MODULE_DEVICE_TABLE(of, gpio_nand_id_table);
+
+static int gpio_nand_of_get_options(struct device *dev,
+ struct gpio_nand_platdata *plat)
+{
+ u32 width;
+
+ if (!of_property_read_u32(dev->of_node, "bank-width", &width)) {
+ if (width == 2) {
+ plat->options |= NAND_BUSWIDTH_16;
+ } else if (width != 1) {
+ dev_err(dev, "invalid bank-width %u\n", width);
+ return -EINVAL;
+ }
+ }
+
+ return 0;
+}
+
+static void gpio_nand_of_get_gpio(struct device *dev,
+ struct gpio_nand_platdata *plat)
+{
+ plat->gpio_rdy = of_get_gpio(dev->of_node, 0);
+ plat->gpio_nce = of_get_gpio(dev->of_node, 1);
+ plat->gpio_ale = of_get_gpio(dev->of_node, 2);
+ plat->gpio_cle = of_get_gpio(dev->of_node, 3);
+ plat->gpio_nwp = of_get_gpio(dev->of_node, 4);
+}
+
+static void gpio_nand_of_get_chip_delay(struct device *dev,
+ struct gpio_nand_platdata *plat)
+{
+ u32 chip_delay;
+
+ if (!of_property_read_u32(dev->of_node, "chip-delay", &chip_delay))
+ plat->chip_delay = (int)chip_delay;
+}
+
+static int gpio_nand_of_get_config(struct device *dev,
+ struct gpio_nand_platdata *plat)
+{
+ int ret = gpio_nand_of_get_options(dev, plat);
+
+ if (ret < 0)
+ return ret;
+
+ gpio_nand_of_get_gpio(dev, plat);
+ gpio_nand_of_get_chip_delay(dev, plat);
+
+ return 0;
+}
+
+static struct resource *gpio_nand_of_get_io_sync(struct device *dev)
+{
+ struct resource *r = kzalloc(sizeof(*r), GFP_KERNEL);
+ u64 addr;
+
+ if (!r)
+ return NULL;
+
+ if (of_property_read_u64(dev->of_node,
+ "gpio-control-nand,io-sync-reg", &addr))
+ goto out_free;
+
+ r->start = addr;
+ r->end = r->start + 0x3;
+ r->flags = IORESOURCE_MEM;
+
+ return r;
+
+out_free:
+ kfree(r);
+
+ return NULL;
+}
+#else /* CONFIG_OF */
+#define gpio_nand_id_table NULL
+static inline int gpio_nand_of_get_config(struct device *dev,
+ struct gpio_nand_platdata *plat)
+{
+ return -ENODEV;
+}
+static inline struct resource *gpio_nand_of_get_io_sync(struct device *dev)
+{
+ return NULL;
+}
+#endif /* CONFIG_OF */
+
static int __devexit gpio_nand_remove(struct platform_device *dev)
{
struct gpiomtd *gpiomtd = platform_get_drvdata(dev);
@@ -178,10 +274,15 @@ static int __devexit gpio_nand_remove(struct platform_device *dev)

nand_release(&gpiomtd->mtd_info);

- res = platform_get_resource(dev, IORESOURCE_MEM, 1);
+ if (!dev->dev.of_node)
+ res = platform_get_resource(dev, IORESOURCE_MEM, 1);
+ else
+ res = gpio_nand_of_get_io_sync(&dev->dev);
iounmap(gpiomtd->io_sync);
if (res)
release_mem_region(res->start, resource_size(res));
+ if (!dev->dev.of_node)
+ kfree(res);

res = platform_get_resource(dev, IORESOURCE_MEM, 0);
iounmap(gpiomtd->nand_chip.IO_ADDR_R);
@@ -226,9 +327,9 @@ static int __devinit gpio_nand_probe(struct platform_device *dev)
struct gpiomtd *gpiomtd;
struct nand_chip *this;
struct resource *res0, *res1;
- int ret;
+ int ret = 0;

- if (!dev->dev.platform_data)
+ if (!dev->dev.of_node && !dev->dev.platform_data)
return -EINVAL;

res0 = platform_get_resource(dev, IORESOURCE_MEM, 0);
@@ -248,7 +349,11 @@ static int __devinit gpio_nand_probe(struct platform_device *dev)
goto err_map;
}

- res1 = platform_get_resource(dev, IORESOURCE_MEM, 1);
+ if (!dev->dev.of_node)
+ res1 = platform_get_resource(dev, IORESOURCE_MEM, 1);
+ else
+ res1 = gpio_nand_of_get_io_sync(&dev->dev);
+
if (res1) {
gpiomtd->io_sync = request_and_remap(res1, 4, "NAND sync", &ret);
if (!gpiomtd->io_sync) {
@@ -257,7 +362,16 @@ static int __devinit gpio_nand_probe(struct platform_device *dev)
}
}

- memcpy(&gpiomtd->plat, dev->dev.platform_data, sizeof(gpiomtd->plat));
+ if (dev->dev.of_node)
+ kfree(res1);
+
+ if (dev->dev.platform_data)
+ memcpy(&gpiomtd->plat, dev->dev.platform_data,
+ sizeof(gpiomtd->plat));
+ else
+ ret = gpio_nand_of_get_config(&dev->dev, &gpiomtd->plat);
+ if (ret)
+ goto err_nce;

ret = gpio_request(gpiomtd->plat.gpio_nce, "NAND NCE");
if (ret)
@@ -312,10 +426,18 @@ static int __devinit gpio_nand_probe(struct platform_device *dev)
goto err_wp;
}

- if (gpiomtd->plat.adjust_parts)
- gpiomtd->plat.adjust_parts(&gpiomtd->plat,
- gpiomtd->mtd_info.size);
+ if (dev->dev.platform_data) {
+ if (gpiomtd->plat.adjust_parts)
+ gpiomtd->plat.adjust_parts(&gpiomtd->plat,
+ gpiomtd->mtd_info.size);
+ } else {
+ ret = of_mtd_parse_partitions(&dev->dev, dev->dev.of_node,
+ &gpiomtd->plat.parts);
+ if (ret < 0)
+ goto err_wp;

+ gpiomtd->plat.num_parts = ret;
+ }
mtd_device_register(&gpiomtd->mtd_info, gpiomtd->plat.parts,
gpiomtd->plat.num_parts);
platform_set_drvdata(dev, gpiomtd);
@@ -352,6 +474,7 @@ static struct platform_driver gpio_nand_driver = {
.remove = gpio_nand_remove,
.driver = {
.name = "gpio-nand",
+ .of_match_table = gpio_nand_id_table,
},
};

--
1.7.4.1