[RFC 6/6] bus: Add support for Tegra NOR controller

[jonathanh@nvidia.com (Jon Hunter)]

On 19/07/16 14:36, Mirza Krak wrote:
> From: Mirza Krak <mirza.krak@gmail.com>
> 
> The NOR bus can be used to connect high-speed devices such as NOR flash,
> FPGAs, DSPs, CAN chips, Wi-Fi chips etc.
> 
> Signed-off-by: Mirza Krak <mirza.krak@gmail.com>
> ---
>  drivers/bus/Kconfig     |   7 +++
>  drivers/bus/Makefile    |   1 +
>  drivers/bus/tegra-nor.c | 118 ++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 126 insertions(+)
>  create mode 100644 drivers/bus/tegra-nor.c
> 
> diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
> index 3b205e2..b74be7d8 100644
> --- a/drivers/bus/Kconfig
> +++ b/drivers/bus/Kconfig
> @@ -145,6 +145,13 @@ config TEGRA_ACONNECT
>  	  Driver for the Tegra ACONNECT bus which is used to interface with
>  	  the devices inside the Audio Processing Engine (APE) for Tegra210.
> 
> +config TEGRA_NOR
> +	tristate "Nvidia Tegra NOR flash bus driver a.k.a GMI/SNOR"
> +		depends on ARCH_TEGRA_2x_SOC || ARCH_TEGRA_3x_SOC
> +		depends on OF
> +		help
> +			Driver for NOR flash bus found on Tegra30/20 SOC`s.

It is actually present on all Tegra's and so I would drop the 30/20.

> +
>  config UNIPHIER_SYSTEM_BUS
>  	tristate "UniPhier System Bus driver"
>  	depends on ARCH_UNIPHIER && OF
> diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
> index ac84cc4..46d0129 100644
> --- a/drivers/bus/Makefile
> +++ b/drivers/bus/Makefile
> @@ -18,5 +18,6 @@ obj-$(CONFIG_OMAP_OCP2SCP)	+= omap-ocp2scp.o
>  obj-$(CONFIG_SUNXI_RSB)		+= sunxi-rsb.o
>  obj-$(CONFIG_SIMPLE_PM_BUS)	+= simple-pm-bus.o
>  obj-$(CONFIG_TEGRA_ACONNECT)	+= tegra-aconnect.o
> +obj-$(CONFIG_TEGRA_NOR)		+= tegra-nor.o
>  obj-$(CONFIG_UNIPHIER_SYSTEM_BUS)	+= uniphier-system-bus.o
>  obj-$(CONFIG_VEXPRESS_CONFIG)	+= vexpress-config.o
> diff --git a/drivers/bus/tegra-nor.c b/drivers/bus/tegra-nor.c
> new file mode 100644
> index 0000000..1e48113
> --- /dev/null
> +++ b/drivers/bus/tegra-nor.c
> @@ -0,0 +1,118 @@
> +/*
> + * Driver for Nvidia NOR Flash bus a.k.a SNOR/GMI.
> + *
> + * Copyright (C) 2016 Host Mobility AB. All rights reserved.
> + *
> + * 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/clk.h>
> +#include <linux/io.h>
> +#include <linux/mfd/syscon.h>

Is this needed?

> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/regmap.h>

Or this?

> +
> +#define TEGRA_NOR_TIMING_REG_COUNT	2
> +
> +#define TEGRA_NOR_CONFIG			0x00
> +#define TEGRA_NOR_STATUS			0x04
> +#define TEGRA_NOR_ADDR_PTR			0x08
> +#define TEGRA_NOR_AHB_ADDR_PTR		0x0c
> +#define TEGRA_NOR_TIMING0			0x10
> +#define TEGRA_NOR_TIMING1			0x14
> +#define TEGRA_NOR_MIO_CONFIG		0x18
> +#define TEGRA_NOR_MIO_TIMING		0x1c
> +#define TEGRA_NOR_DMA_CONFIG		0x20
> +#define TEGRA_NOR_CS_MUX_CONFIG		0x24

Not all of these are used. It is good to define them and I wonder if we
should add support for MIO while are at it :-)

> +
> +#define TEGRA_NOR_CONFIG_GO				BIT(31)
> +
> +static const struct of_device_id nor_id_table[] = {
> +	/* Tegra30 */

I don't think this comment is needed.

> +	{ .compatible = "nvidia,tegra30-nor", .data = NULL, },

You don't need to set data to NULL.

> +	/* Tegra20 */
> +	{ .compatible = "nvidia,tegra20-nor", .data = NULL, },

Same here.

> +
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, nor_id_table);
> +
> +
> +static int __init nor_parse_dt(struct platform_device *pdev,
> +				void __iomem *base)
> +{
> +	struct device_node *of_node = pdev->dev.of_node;
> +	u32 config, timing[TEGRA_NOR_TIMING_REG_COUNT];
> +	int ret;
> +
> +	ret = of_property_read_u32_array(of_node, "nvidia,cs-timing",
> +					 timing, TEGRA_NOR_TIMING_REG_COUNT);
> +	if (!ret) {
> +		writel(timing[0], base + TEGRA_NOR_TIMING0);
> +		writel(timing[1], base + TEGRA_NOR_TIMING1);
> +	}
> +
> +	ret = of_property_read_u32(of_node, "nvidia,config", &config);
> +	if (ret)
> +		return ret;
> +
> +	config |= TEGRA_NOR_CONFIG_GO;
> +	writel(config, base + TEGRA_NOR_CONFIG);
> +
> +	if (of_get_child_count(of_node))
> +		ret = of_platform_populate(of_node,
> +				   of_default_bus_match_table,
> +				   NULL, &pdev->dev);
> +
> +	return ret;
> +}
> +
> +static int __init nor_probe(struct platform_device *pdev)
> +{

I would drop the __init.

> +	struct resource *res;
> +	struct clk *clk;
> +	void __iomem *base;
> +	int ret;
> +
> +	/* get the resource */
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(base))
> +		return PTR_ERR(base);
> +
> +	/* get the clock */
> +	clk = devm_clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(clk))
> +		return PTR_ERR(clk);
> +
> +	ret = clk_prepare_enable(clk);
> +	if (ret)
> +		return ret;
> +
> +	/* parse the device node */
> +	ret = nor_parse_dt(pdev, base);
> +	if (ret) {
> +		dev_err(&pdev->dev, "%s fail to create devices.\n",
> +			pdev->dev.of_node->full_name);
> +		clk_disable_unprepare(clk);
> +		return ret;
> +	}
> +
> +	dev_info(&pdev->dev, "Driver registered.\n");
> +	return 0;
> +}
> +
> +static struct platform_driver nor_driver = {
> +	.driver = {
> +		.name		= "tegra-nor",
> +		.of_match_table	= nor_id_table,
> +	},
> +};

The driver should have a remove function given that we can build as a
module.

> +module_platform_driver_probe(nor_driver, nor_probe);

I would use "tegra_nor" namespace for all the structs, functions, etc.
However, we may prefer to go with GMI and in which case tegra_gmi_probe,
etc.

Cheers
Jon

-- 
nvpublic