Re: [RESEND RFC 3/3] nvmem: Add 'nvmem-composite' driver

[Srinivas Kandagatla <srinivas.kandagatla@linaro.org>]

On 01/03/16 16:59, Andrey Smirnov wrote:
> Add 'nvmem-composite' driver which allows to combine multiple chunks of
> various NVMEM cells into a single continuous NVMEM device.

My plan on this feature was add support inside the nvmem_cell_get 
itself, this makes the nvmem bindings more inline with bindings like 
pinctrl.
Also I still want to keep nvmem simple as it can.

DT would look something like this.

nvmem-provider-a {
	cell_a {
		reg = <0 2>;
	};
};

nvmem-provider-b {
	cell_b: cell_c {
		reg = <0 1>;
	};
};

nvmem-provider-c {
	cell_c: cell_c {
		reg = <3 2>;
	}
};

a-node {
	nvmem-cells = <&cell_a &cell_b &cell_c>
	nvmem-cell-names = "some-data";
};


thanks,
srini

>
> Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
> ---
>   .../devicetree/bindings/nvmem/composite.txt        |  44 ++++
>   drivers/nvmem/Makefile                             |   1 +
>   drivers/nvmem/composite.c                          | 225 +++++++++++++++++++++
>   3 files changed, 270 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/nvmem/composite.txt
>   create mode 100644 drivers/nvmem/composite.c
>
> diff --git a/Documentation/devicetree/bindings/nvmem/composite.txt b/Documentation/devicetree/bindings/nvmem/composite.txt
> new file mode 100644
> index 0000000..e24cf4b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/nvmem/composite.txt
> @@ -0,0 +1,44 @@
> += NVMEM cell compositor =
> +
> +This binding is designed to provide a way for a developer to combine
> +portions of other NVMEM cell and acces that data as a signle NVMEM
> +cell using NVMEM consumer API.
> +
> +Required properties:
> +- compatible: should be "nvmem-composite"
> +- layout: specifies which sources comprise data in nvmem device
> +  	  format is "<nvmem-cell-phandle offset size>"
> +
> += Data cells =
> +Are child nodes of nvmem-composite, bindings of which as described in
> +bindings/nvmem/nvmem.txt
> +
> +Example:
> +
> +	composite-nvmem {
> +		compatible = "nvmem-composite";
> +		layout = <&another_cell_a 0 2
> + 			  &another_cell_b 0 1
> +			  &another_cell_c 3 2>;
> +
> +		cell1: cell@0 {
> +			reg = <0 5>;
> +		};
> +	}
> +
> +the result of reading variable cell1 would be:
> +
> +[a[0] a[1] b[0] c[3] c[4]],
> +
> +where a[i], b[i], c[i], represnet i-th bytes of NVMEM cells
> +another_cell_a, another_cell_b and another_cell_c respectively
> +
> += Data consumers =
> +Are device nodes which consume nvmem data cells.
> +
> +Example:
> +
> +	a-node {
> +		nvmem-cells = <&cell1>;
> +		nvmem-cell-names = "some-data";
> +	};
> diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
> index 1a1adba..49c0eca 100644
> --- a/drivers/nvmem/Makefile
> +++ b/drivers/nvmem/Makefile
> @@ -19,3 +19,4 @@ nvmem_sunxi_sid-y		:= sunxi_sid.o
>   obj-$(CONFIG_NVMEM_VF610_OCOTP)	+= nvmem-vf610-ocotp.o
>   nvmem-vf610-ocotp-y		:= vf610-ocotp.o
>   obj-y += blob.o
> +obj-y += composite.o
> diff --git a/drivers/nvmem/composite.c b/drivers/nvmem/composite.c
> new file mode 100644
> index 0000000..cf01590
> --- /dev/null
> +++ b/drivers/nvmem/composite.c
> @@ -0,0 +1,225 @@
> +#define DEBUG 1
> +
> +#include <linux/device.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/nvmem-provider.h>
> +#include <linux/nvmem-consumer.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/slab.h>
> +
> +struct nvmem_composite {
> +	struct device *dev;
> +	struct list_head layout;
> +	size_t layout_size;
> +};
> +
> +struct nvmem_composite_item {
> +	struct nvmem_cell *cell;
> +	unsigned int idx, start, end, size;
> +	struct list_head node;
> +};
> +
> +static struct nvmem_composite_item *
> +nvmem_composite_find_first(struct nvmem_composite *ncomp,
> +			   unsigned int offset)
> +{
> +	struct nvmem_composite_item *first;
> +	list_for_each_entry(first, &ncomp->layout, node) {
> +		/*
> +		 * Skip all of the irrelevant items that end before our offset
> +		 */
> +		if (first->end > offset)
> +			return first;
> +	}
> +
> +	return NULL;
> +}
> +
> +static int nvmem_composite_read(void *context,
> +				const void *reg, size_t reg_size,
> +				void *val, size_t val_size)
> +{
> +	struct nvmem_composite *ncomp = context;
> +	const unsigned int offset = *(u32 *)reg;
> +	void *dst = val;
> +	size_t residue = val_size;
> +	struct nvmem_composite_item *item, *first;
> +	uint8_t *data;
> +	unsigned int size, chunk, ii;
> +
> +
> +	first = item = nvmem_composite_find_first(ncomp, offset);
> +	if (!first) {
> +		dev_dbg(ncomp->dev, "Invalid offset\n");
> +		return -EINVAL;
> +	}
> +
> +	list_for_each_entry_from(item, &ncomp->layout, node) {
> +		/*
> +		 * If our first read is not located on item boundary
> +		 * we have to introduce artificial offset
> +		 */
> +		ii = (item == first) ? offset - first->start : 0;
> +
> +		data = nvmem_cell_read(item->cell, &size);
> +		if (IS_ERR(data)) {
> +			dev_dbg(ncomp->dev, "Failed to read nvmem cell\n");
> +			return PTR_ERR(data);
> +		}
> +
> +		chunk = min(residue, item->size - ii);
> +		memcpy(dst, &data[item->idx + ii], chunk);
> +		kfree(data);
> +
> +		dst += chunk;
> +		residue -= chunk;
> +	}
> +
> +	return (residue) ? -EINVAL : 0;
> +}
> +
> +static int nvmem_composite_write(void *context, const void *data,
> +				 size_t count)
> +{
> +	return -ENOTSUPP;
> +}
> +
> +static const struct regmap_bus nvmem_composite_regmap_bus = {
> +	.write = nvmem_composite_write,
> +	.read  = nvmem_composite_read,
> +};
> +
> +static int nvmem_composite_validate_dt(struct device_node *np)
> +{
> +	/* FIXME */
> +	return 0;
> +}
> +
> +static int nvmem_composite_probe(struct platform_device *pdev)
> +{
> +	int i, ret;
> +	unsigned int start = 0;
> +	unsigned int len;
> +	struct device *dev = &pdev->dev;
> +	struct device_node *np = dev->of_node;
> +	struct nvmem_device *nvmem;
> +	struct nvmem_composite *ncomp;
> +	struct regmap *map;
> +	struct nvmem_composite_item *item;
> +	struct nvmem_config  nv_cnf = {0};
> +	struct regmap_config rm_cnf = {0};
> +	const __be32 *addr;
> +	unsigned int item_count;
> +
> +	ret = nvmem_composite_validate_dt(np);
> +	if (ret < 0) {
> +		dev_dbg(dev, "Device validation failed\n");
> +		return ret;
> +	}
> +
> +	ncomp = devm_kzalloc(dev, sizeof(*ncomp), GFP_KERNEL);
> +	INIT_LIST_HEAD(&ncomp->layout);
> +	ncomp->dev = dev;
> +	
> +	addr = of_get_property(np, "layout", &len);
> +	item_count = len / (3 * sizeof(__be32));
> +
> +	for (i = 0; i < item_count; i++) {
> +		struct device_node *cell_np;
> +		uint32_t phandle;
> +
> +		item = devm_kzalloc(dev, sizeof(*item), GFP_KERNEL);
> +
> +		phandle = be32_to_cpup(addr++);
> +		cell_np = of_find_node_by_phandle(phandle);
> +		if (!cell_np) {
> +			dev_dbg(dev,
> +				"Couldn't find nvmem cell by its phandle\n");
> +			return -ENOENT;
> +		}
> +
> +		item->cell = of_nvmem_cell_from_device_node(cell_np);
> +		if (IS_ERR(item->cell)) {
> +			dev_dbg(dev,
> +				"Failed to instantiate nvmem cell from "
> +				"a device tree node\n");
> +			ret = PTR_ERR(item->cell);
> +			goto unwind;
> +		}
> +
> +		item->start = start;
> +		item->idx = be32_to_cpup(addr++);
> +		item->size = be32_to_cpup(addr++);
> +		item->end  = item->size - 1;
> +		ncomp->layout_size += item->size;
> +		start += item->size;
> +
> +		list_add_tail(&item->node, &ncomp->layout);
> +	}
> +
> +	rm_cnf.reg_bits = 32;
> +	rm_cnf.val_bits = 8;
> +	rm_cnf.reg_stride = 1;
> +	rm_cnf.name = "nvmem-composite";
> +	rm_cnf.max_register = ncomp->layout_size - 1;
> +
> +	map = devm_regmap_init(dev,
> +			       &nvmem_composite_regmap_bus,
> +			       ncomp,
> +			       &rm_cnf);
> +	if (IS_ERR(map)) {
> +		dev_dbg(dev, "Failed to initilize regmap\n");
> +		return PTR_ERR(map);
> +	}
> +
> +	nv_cnf.name = "nvmem-composite";
> +	nv_cnf.read_only = true;
> +	nv_cnf.dev = dev;
> +
> +	nvmem = nvmem_register(&nv_cnf);
> +	if (IS_ERR(nvmem)) {
> +		dev_dbg(dev, "Failed to register 'nvmem' device\n");
> +		return PTR_ERR(nvmem);
> +	}
> +
> +	platform_set_drvdata(pdev, nvmem);
> +	return 0;
> +unwind:
> +	/* FIXME  */
> +	return ret;
> +}
> +
> +static int nvmem_composite_remove(struct platform_device *pdev)
> +{
> +	struct nvmem_device *nvmem = platform_get_drvdata(pdev);
> +
> +	/*
> +	   FIXME free allocated nvmem cells
> +	 */
> +	return nvmem_unregister(nvmem);
> +}
> +
> +
> +static const struct of_device_id nvmem_composite_dt_ids[] = {
> +	{ .compatible = "nvmem-composite", },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, nvmem_composite_dt_ids);
> +
> +static struct platform_driver nvmem_composite_driver = {
> +	.probe	= nvmem_composite_probe,
> +	.remove	= nvmem_composite_remove,
> +	.driver = {
> +		.name	= "nvmem-composite",
> +		.of_match_table = nvmem_composite_dt_ids,
> +	},
> +};
> +module_platform_driver(nvmem_composite_driver);
> +
> +MODULE_AUTHOR("Andrey Smirnov <andrew.smirnov@gmail.com>");
> +MODULE_DESCRIPTION("FIXME");
> +MODULE_LICENSE("GPL v2");
>