Re: [RFC PATCH] mtd: nand: Add OX820 NAND Support

From: Boris Brezillon
Date: Tue Oct 18 2016 - 16:18:05 EST

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Hi Neil,

On Tue, 18 Oct 2016 11:09:27 +0200
Neil Armstrong <narmstrong@xxxxxxxxxxxx> wrote:

> Add NAND driver to support the Oxford Semiconductor OX820 NAND Controller.
> This is a simple memory mapped NAND controller with single chip select and
> software ECC.
>
> Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> ---
> .../devicetree/bindings/mtd/oxnas-nand.txt | 24 ++++
> drivers/mtd/nand/Kconfig | 5 +
> drivers/mtd/nand/Makefile | 1 +
> drivers/mtd/nand/oxnas_nand.c | 144 +++++++++++++++++++++
> 4 files changed, 174 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/mtd/oxnas-nand.txt
> create mode 100644 drivers/mtd/nand/oxnas_nand.c
>
> diff --git a/Documentation/devicetree/bindings/mtd/oxnas-nand.txt b/Documentation/devicetree/bindings/mtd/oxnas-nand.txt
> new file mode 100644
> index 0000000..83b684d
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mtd/oxnas-nand.txt
> @@ -0,0 +1,24 @@
> +* Oxford Semiconductor OXNAS NAND Controller
> +
> +Please refer to nand.txt for generic information regarding MTD NAND bindings.
> +
> +Required properties:
> + - compatible: "oxsemi,ox820-nand"
> + - reg: Base address and length for NAND mapped memory.
> +
> +Optional Properties:
> + - clocks: phandle to the NAND gate clock if needed.
> + - resets: phandle to the NAND reset control if needed.
> +
> +Example:
> +
> +nand: nand@41000000 {
> + compatible = "oxsemi,ox820-nand";
> + reg = <0x41000000 0x100000>;
> + nand-ecc-mode = "soft";
> + clocks = <&stdclk CLK_820_NAND>;
> + resets = <&reset RESET_NAND>;
> + #address-cells = <1>;
> + #size-cells = <1>;
> + status = "disabled";
> +};

Can you switch to new DT representation for NAND controllers, with one
node for the NAND controller and NAND devices connected to this NAND
controller defined as sub-nodes of this NAND controller [1]?

> diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
> index 7b7a887..c023125 100644
> --- a/drivers/mtd/nand/Kconfig
> +++ b/drivers/mtd/nand/Kconfig
> @@ -426,6 +426,11 @@ config MTD_NAND_ORION
> No board specific support is done by this driver, each board
> must advertise a platform_device for the driver to attach.
>
> +config MTD_NAND_OXNAS
> + tristate "NAND Flash support for Oxford Semiconductor SoC"
> + help
> + This enables the NAND flash controller on Oxford Semiconductor SoCs.
> +
> config MTD_NAND_FSL_ELBC
> tristate "NAND support for Freescale eLBC controllers"
> depends on FSL_SOC
> diff --git a/drivers/mtd/nand/Makefile b/drivers/mtd/nand/Makefile
> index cafde6f..05fc054 100644
> --- a/drivers/mtd/nand/Makefile
> +++ b/drivers/mtd/nand/Makefile
> @@ -35,6 +35,7 @@ obj-$(CONFIG_MTD_NAND_TMIO) += tmio_nand.o
> obj-$(CONFIG_MTD_NAND_PLATFORM) += plat_nand.o
> obj-$(CONFIG_MTD_NAND_PASEMI) += pasemi_nand.o
> obj-$(CONFIG_MTD_NAND_ORION) += orion_nand.o
> +obj-$(CONFIG_MTD_NAND_OXNAS) += oxnas_nand.o
> obj-$(CONFIG_MTD_NAND_FSL_ELBC) += fsl_elbc_nand.o
> obj-$(CONFIG_MTD_NAND_FSL_IFC) += fsl_ifc_nand.o
> obj-$(CONFIG_MTD_NAND_FSL_UPM) += fsl_upm.o
> diff --git a/drivers/mtd/nand/oxnas_nand.c b/drivers/mtd/nand/oxnas_nand.c
> new file mode 100644
> index 0000000..ee402ab
> --- /dev/null
> +++ b/drivers/mtd/nand/oxnas_nand.c
> @@ -0,0 +1,144 @@
> +/*
> + * Oxford Semiconductor OXNAS NAND driver
> + *
> + * Heavily based on plat_nand.c :
> + * Author: Vitaly Wool <vitalywool@xxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + */
> +
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/clk.h>
> +#include <linux/reset.h>
> +#include <linux/mtd/mtd.h>
> +#include <linux/mtd/nand.h>
> +#include <linux/mtd/partitions.h>
> +
> +/* nand commands */
> +#define NAND_CMD_ALE BIT(18)
> +#define NAND_CMD_CLE BIT(19)
> +#define NAND_CMD_CS 0

I guess this is zero here because you only support connecting a NAND to
CS0.
It's probably something like

OX820_NAND_CS(x) ((x) << CS_FIELD_SHIFT)

> +#define NAND_CMD_RESET 0xff

Why do you have to redefine it? it's already defined here [2].

> +#define NAND_CMD (NAND_CMD_CS | NAND_CMD_CLE)
> +#define NAND_ADDR (NAND_CMD_CS | NAND_CMD_ALE)
> +#define NAND_DATA (NAND_CMD_CS)

Please prefix those macros with OX820, has stated above, this can
conflict with generic definitions.
Also, I'm not sure you should pass the CS information here.

> +
> +struct oxnas_nand_data {
> + struct nand_chip chip;
> + void __iomem *io_base;
> + struct clk *clk;
> +};

Even if your driver does not seem to support connecting several chips
to the same controller, I'd like you to clearly separate the NAND
controller and NAND chip objects:

#define OXNAS_NAND_MAX_CHIPS 1

struct oxnas_nand_controller {
struct nand_hw_control base;
void __iomem *io_base;
struct clk *clk;
struct nand_chip *chips[OXNAS_NAND_MAX_CHIPS];
}

> +
> +static void oxnas_nand_cmd_ctrl(struct mtd_info *mtd, int cmd,
> + unsigned int ctrl)
> +{
> + struct nand_chip *this = mtd->priv;
> + unsigned long nandaddr = (unsigned long) this->IO_ADDR_W;

Please use the ->io_base field directly, and do not use ->IO_ADDR_W/R
(I'd like to get rid of them at some point).

Also, declare the nandaddr as a void __iomem *, and use the '+'
operator instead of '|'.

> +
> + if (ctrl & NAND_CTRL_CHANGE) {
> + nandaddr &= ~(NAND_CMD | NAND_ADDR);

This is not needed.

> + if (ctrl & NAND_CLE)
> + nandaddr |= NAND_CMD;
> + else if (ctrl & NAND_ALE)
> + nandaddr |= NAND_ADDR;
> + this->IO_ADDR_W = (void __iomem *) nandaddr;

This is not needed, is it?

> + }
> +
> + if (cmd != NAND_CMD_NONE)
> + writeb(cmd, (void __iomem *) nandaddr);
> +}
> +
> +/*
> + * Probe for the NAND device.
> + */
> +static int oxnas_nand_probe(struct platform_device *pdev)
> +{
> + struct oxnas_nand_data *data;
> + struct mtd_info *mtd;
> + struct resource *res;
> + int err = 0;
> +
> + /* Allocate memory for the device structure (and zero it) */
> + data = devm_kzalloc(&pdev->dev, sizeof(struct oxnas_nand_data),
> + GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + data->io_base = devm_ioremap_resource(&pdev->dev, res);
> + if (IS_ERR(data->io_base))
> + return PTR_ERR(data->io_base);
> +
> + data->clk = devm_clk_get(&pdev->dev, NULL);
> + if (IS_ERR(data->clk))
> + data->clk = NULL;
> +
> + nand_set_flash_node(&data->chip, pdev->dev.of_node);
> + mtd = nand_to_mtd(&data->chip);
> + mtd->dev.parent = &pdev->dev;
> + mtd->priv = &data->chip;
> +
> + data->chip.IO_ADDR_R = data->io_base;
> + data->chip.IO_ADDR_W = data->io_base;

As I said above, don't use these fields.

> + data->chip.cmd_ctrl = oxnas_nand_cmd_ctrl;
> + data->chip.chip_delay = 30;
> + data->chip.ecc.mode = NAND_ECC_SOFT;
> + data->chip.ecc.algo = NAND_ECC_HAMMING;

Probably a good idea to support soft ECC as well...

> +
> + platform_set_drvdata(pdev, data);
> +
> + clk_prepare_enable(data->clk);
> + device_reset_optional(&pdev->dev);
> +
> + /* Scan to find existence of the device */
> + if (nand_scan(mtd, 1)) {

Why not returning nand_scan() error code?

> + err = -ENXIO;
> + goto out;

Return directly here.

> + }
> +
> + err = mtd_device_parse_register(mtd, NULL, NULL, NULL, 0);

Use mtd_device_register() here.

> + if (!err)
> + return err;
> +
> + nand_release(mtd);

Why not

if (err)
nand_release(mtd);

> +out:

Drop this label.

> + return err;
> +}
> +
> +static int oxnas_nand_remove(struct platform_device *pdev)
> +{
> + struct oxnas_nand_data *data = platform_get_drvdata(pdev);
> +
> + nand_release(nand_to_mtd(&data->chip));
> +
> + return 0;
> +}
> +
> +static const struct of_device_id oxnas_nand_match[] = {
> + { .compatible = "oxsemi,ox820-nand" },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, oxnas_nand_match);
> +
> +static struct platform_driver oxnas_nand_driver = {
> + .probe = oxnas_nand_probe,
> + .remove = oxnas_nand_remove,
> + .driver = {
> + .name = "oxnas_nand",
> + .of_match_table = oxnas_nand_match,
> + },
> +};
> +
> +module_platform_driver(oxnas_nand_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Vitaly Wool");
> +MODULE_DESCRIPTION("Oxnas NAND driver");
> +MODULE_ALIAS("platform:oxnas_nand");

Thanks,

Boris

[1]https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/mtd/nand.txt?id=refs/tags/v4.9-rc1#n57
[2]http://lxr.free-electrons.com/source/include/linux/mtd/nand.h#L90

Next message: Richard Weinberger: "Re: [PATCH 1/1] MAINTAINERS: add a maintainer for the SPI NOR subsystem"
Previous message: Parav Pandit: "Re: [PATCHv12 1/3] rdmacg: Added rdma cgroup controller"
In reply to: Neil Armstrong: "Re: [RFC PATCH] mtd: nand: Add OX820 NAND Support"
Next in thread: Neil Armstrong: "Re: [RFC PATCH] mtd: nand: Add OX820 NAND Support"
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