Subject: Re: [PATCH V3 6/6] bus: Add support for Tegra Generic Memory
 Interface
To: Mirza Krak <mirza.krak@gmail.com>, <swarren@wwwdotorg.org>,
        <thierry.reding@gmail.com>
References: <1477576872-2665-1-git-send-email-mirza.krak@gmail.com>
 <1477576872-2665-7-git-send-email-mirza.krak@gmail.com>
CC: <gnurou@gmail.com>, <linux@armlinux.org.uk>, <pdeschrijver@nvidia.com>,
        <pgaikwad@nvidia.com>, <mturquette@baylibre.com>,
        <sboyd@codeaurora.org>, <robh+dt@kernel.org>, <mark.rutland@arm.com>,
        <devicetree@vger.kernel.org>, <linux-tegra@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-arm-kernel@lists.infradead.org>,
        <linux-clk@vger.kernel.org>
From: Jon Hunter <jonathanh@nvidia.com>
Message-ID: <3cdf7281-840f-1aa0-5a57-fe58501165f4@nvidia.com>
Date: Thu, 3 Nov 2016 10:51:19 +0000
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On 27/10/16 15:01, Mirza Krak wrote:
> From: Mirza Krak <mirza.krak@gmail.com>
>
> The Generic Memory Interface bus can be used to connect high-speed
> devices such as NOR flash, FPGAs, DSPs...
>
> Signed-off-by: Mirza Krak <mirza.krak@gmail.com>
> Tested-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
> Tested-on: Colibri T20/T30 on EvalBoard V3.x and GMI-Memory Board
> ---
>
> Changes in v2:
>  - Fixed some checkpatch errors
>  - Re-ordered probe to get rid of local variables
>  - Moved of_platform_default_populate call to the end of probe
>  - Use the timing and configuration properties from the child device
>  - Added warning if more then 1 child device exist
>
> Changes in v3:
>  - added helper function to disable the controller which is used in remove and
>  on error.
>  - Added logic to parse CS# from "ranges" property with fallback to "reg"
>  property
>
>  drivers/bus/Kconfig     |   8 ++
>  drivers/bus/Makefile    |   1 +
>  drivers/bus/tegra-gmi.c | 267 ++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 276 insertions(+)
>  create mode 100644 drivers/bus/tegra-gmi.c
>
> diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
> index 4ed7d26..2e75a7f 100644
> --- a/drivers/bus/Kconfig
> +++ b/drivers/bus/Kconfig
> @@ -141,6 +141,14 @@ 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_GMI
> +	tristate "Tegra Generic Memory Interface bus driver"
> +	depends on ARCH_TEGRA
> +	help
> +	  Driver for the Tegra Generic Memory Interface bus which can be used
> +	  to attach devices such as NOR, UART, FPGA and more.
> +
> +

Nit-pick ... only one additional line above is needed to be consistent 
with the rest of the file.

>  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..34e2bab 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-$(CONFIG_TEGRA_GMI)		+= tegra-gmi.o
>  obj-$(CONFIG_UNIPHIER_SYSTEM_BUS)	+= uniphier-system-bus.o
>  obj-$(CONFIG_VEXPRESS_CONFIG)	+= vexpress-config.o
> diff --git a/drivers/bus/tegra-gmi.c b/drivers/bus/tegra-gmi.c
> new file mode 100644
> index 0000000..dd9623e
> --- /dev/null
> +++ b/drivers/bus/tegra-gmi.c
> @@ -0,0 +1,267 @@
> +/*
> + * Driver for NVIDIA Generic Memory Interface
> + *
> + * 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/delay.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/reset.h>
> +
> +#define TEGRA_GMI_CONFIG		0x00
> +#define TEGRA_GMI_CONFIG_GO		BIT(31)
> +#define TEGRA_GMI_BUS_WIDTH_32BIT	BIT(30)
> +#define TEGRA_GMI_MUX_MODE		BIT(28)
> +#define TEGRA_GMI_RDY_BEFORE_DATA	BIT(24)
> +#define TEGRA_GMI_RDY_ACTIVE_HIGH	BIT(23)
> +#define TEGRA_GMI_ADV_ACTIVE_HIGH	BIT(22)
> +#define TEGRA_GMI_OE_ACTIVE_HIGH	BIT(21)
> +#define TEGRA_GMI_CS_ACTIVE_HIGH	BIT(20)
> +#define TEGRA_GMI_CS_SELECT(x)		((x & 0x7) << 4)
> +
> +#define TEGRA_GMI_TIMING0		0x10
> +#define TEGRA_GMI_MUXED_WIDTH(x)	((x & 0xf) << 12)
> +#define TEGRA_GMI_HOLD_WIDTH(x)		((x & 0xf) << 8)
> +#define TEGRA_GMI_ADV_WIDTH(x)		((x & 0xf) << 4)
> +#define TEGRA_GMI_CE_WIDTH(x)		(x & 0xf)
> +
> +#define TEGRA_GMI_TIMING1		0x14
> +#define TEGRA_GMI_WE_WIDTH(x)		((x & 0xff) << 16)
> +#define TEGRA_GMI_OE_WIDTH(x)		((x & 0xff) << 8)
> +#define TEGRA_GMI_WAIT_WIDTH(x)		(x & 0xff)
> +
> +struct tegra_gmi_priv {
> +	void __iomem *base;
> +	struct reset_control *rst;
> +	struct clk *clk;
> +
> +	u32 snor_config;
> +	u32 snor_timing0;
> +	u32 snor_timing1;
> +};
> +
> +static void tegra_gmi_disable(struct tegra_gmi_priv *priv)
> +{
> +	u32 config;
> +
> +	/* stop GMI operation */
> +	config = readl(priv->base + TEGRA_GMI_CONFIG);
> +	config &= ~TEGRA_GMI_CONFIG_GO;
> +	writel(config, priv->base + TEGRA_GMI_CONFIG);
> +
> +	reset_control_assert(priv->rst);
> +	clk_disable_unprepare(priv->clk);
> +}
> +
> +static void tegra_gmi_init(struct device *dev, struct tegra_gmi_priv *priv)
> +{
> +	writel(priv->snor_timing0, priv->base + TEGRA_GMI_TIMING0);
> +	writel(priv->snor_timing1, priv->base + TEGRA_GMI_TIMING1);
> +
> +	priv->snor_config |= TEGRA_GMI_CONFIG_GO;
> +	writel(priv->snor_config, priv->base + TEGRA_GMI_CONFIG);
> +}
> +
> +static int tegra_gmi_parse_dt(struct device *dev, struct tegra_gmi_priv *priv)
> +{
> +	struct device_node *child = of_get_next_available_child(dev->of_node,
> +		NULL);
> +	u32 property, ranges[4];
> +	int ret;
> +
> +	if (!child) {
> +		dev_warn(dev, "no child nodes found\n");
> +		return 0;

Don't we want to return an error here? Otherwise, we will call 
tegra_gmi_init() with an invalid configuration.

> +	}
> +
> +	/*
> +	 * We currently only support one child device due to lack of
> +	 * chip-select address decoding. Which means that we only have one
> +	 * chip-select line from the GMI controller.
> +	 */
> +	if (of_get_child_count(dev->of_node) > 1)
> +		dev_warn(dev, "only one child device is supported.");
> +
> +	if (of_property_read_bool(child, "nvidia,snor-data-width-32bit"))
> +		priv->snor_config |= TEGRA_GMI_BUS_WIDTH_32BIT;
> +
> +	if (of_property_read_bool(child, "nvidia,snor-mux-mode"))
> +		priv->snor_config |= TEGRA_GMI_MUX_MODE;
> +
> +	if (of_property_read_bool(child, "nvidia,snor-rdy-active-before-data"))
> +		priv->snor_config |= TEGRA_GMI_RDY_BEFORE_DATA;
> +
> +	if (of_property_read_bool(child, "nvidia,snor-rdy-inv"))
> +		priv->snor_config |= TEGRA_GMI_RDY_ACTIVE_HIGH;
> +
> +	if (of_property_read_bool(child, "nvidia,snor-adv-inv"))
> +		priv->snor_config |= TEGRA_GMI_ADV_ACTIVE_HIGH;
> +
> +	if (of_property_read_bool(child, "nvidia,snor-oe-inv"))
> +		priv->snor_config |= TEGRA_GMI_OE_ACTIVE_HIGH;
> +
> +	if (of_property_read_bool(child, "nvidia,snor-cs-inv"))
> +		priv->snor_config |= TEGRA_GMI_CS_ACTIVE_HIGH;
> +
> +	/* Decode the CS# */
> +	ret = of_property_read_u32_array(child, "ranges", ranges, 4);
> +	if (ret < 0) {
> +		/* Invalid binding */
> +		if (ret == -EOVERFLOW) {
> +			dev_err(dev, "invalid ranges length\n");
> +			goto error_cs_decode;
> +		}
> +
> +		/*
> +		 * If we reach here it means that the child node has an empty
> +		 * ranges or it does not exist at all. Attempt to decode the
> +		 * CS# from the reg property instead.
> +		 */
> +		ret = of_property_read_u32(child, "reg", &property);
> +		if (ret < 0) {
> +			dev_err(dev, "no reg property found\n");
> +			goto error_cs_decode;
> +		}
> +	} else {
> +		property = ranges[1];
> +	}
> +
> +	priv->snor_config |= TEGRA_GMI_CS_SELECT(property);

Should we make sure the CS is a valid value before setting?

> +
> +	/* The default values that are provided below are reset values */
> +	if (!of_property_read_u32(child, "nvidia,snor-muxed-width", &property))
> +		priv->snor_timing0 |= TEGRA_GMI_MUXED_WIDTH(property);
> +	else
> +		priv->snor_timing0 |= TEGRA_GMI_MUXED_WIDTH(1);
> +
> +	if (!of_property_read_u32(child, "nvidia,snor-hold-width", &property))
> +		priv->snor_timing0 |= TEGRA_GMI_HOLD_WIDTH(property);
> +	else
> +		priv->snor_timing0 |= TEGRA_GMI_HOLD_WIDTH(1);
> +
> +	if (!of_property_read_u32(child, "nvidia,snor-adv-width", &property))
> +		priv->snor_timing0 |= TEGRA_GMI_ADV_WIDTH(property);
> +	else
> +		priv->snor_timing0 |= TEGRA_GMI_ADV_WIDTH(1);
> +
> +	if (!of_property_read_u32(child, "nvidia,snor-ce-width", &property))
> +		priv->snor_timing0 |= TEGRA_GMI_CE_WIDTH(property);
> +	else
> +		priv->snor_timing0 |= TEGRA_GMI_CE_WIDTH(4);
> +
> +	if (!of_property_read_u32(child, "nvidia,snor-we-width", &property))
> +		priv->snor_timing1 |= TEGRA_GMI_WE_WIDTH(property);
> +	else
> +		priv->snor_timing1 |= TEGRA_GMI_WE_WIDTH(1);
> +
> +	if (!of_property_read_u32(child, "nvidia,snor-oe-width", &property))
> +		priv->snor_timing1 |= TEGRA_GMI_OE_WIDTH(property);
> +	else
> +		priv->snor_timing1 |= TEGRA_GMI_OE_WIDTH(1);
> +
> +	if (!of_property_read_u32(child, "nvidia,snor-wait-width", &property))
> +		priv->snor_timing1 |= TEGRA_GMI_WAIT_WIDTH(property);
> +	else
> +		priv->snor_timing1 |= TEGRA_GMI_WAIT_WIDTH(3);
> +
> +error_cs_decode:
> +	if (ret < 0)
> +		dev_err(dev, "failed to decode chip-select number\n");

Nit do we need another error message here? Can we add the "failed to 
decode CS" part the earlier message?

> +
> +	of_node_put(child);
> +	return ret;
> +}
> +
> +static int tegra_gmi_probe(struct platform_device *pdev)
> +{
> +	struct resource *res;
> +	struct device *dev = &pdev->dev;
> +	struct tegra_gmi_priv *priv;
> +	int ret;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	priv->base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(priv->base))
> +		return PTR_ERR(priv->base);
> +
> +	priv->clk = devm_clk_get(dev, "gmi");
> +	if (IS_ERR(priv->clk)) {
> +		dev_err(dev, "can not get clock\n");
> +		return PTR_ERR(priv->clk);
> +	}
> +
> +	priv->rst = devm_reset_control_get(dev, "gmi");
> +	if (IS_ERR(priv->rst)) {
> +		dev_err(dev, "can not get reset\n");
> +		return PTR_ERR(priv->rst);
> +	}
> +
> +	ret = tegra_gmi_parse_dt(dev, priv);
> +	if (ret)
> +		return ret;
> +
> +	ret = clk_prepare_enable(priv->clk);
> +	if (ret) {
> +		dev_err(dev, "fail to enable clock.\n");
> +		return ret;
> +	}
> +
> +	reset_control_assert(priv->rst);
> +	udelay(2);
> +	reset_control_deassert(priv->rst);
> +
> +	tegra_gmi_init(dev, priv);
> +
> +	ret = of_platform_default_populate(dev->of_node, NULL, dev);
> +	if (ret < 0) {
> +		dev_err(dev, "fail to create devices.\n");
> +		tegra_gmi_disable(priv);
> +		return ret;
> +	}
> +
> +	dev_set_drvdata(dev, priv);
> +
> +	return 0;
> +}
> +
> +static int tegra_gmi_remove(struct platform_device *pdev)
> +{
> +	struct tegra_gmi_priv *priv = dev_get_drvdata(&pdev->dev);
> +
> +	of_platform_depopulate(&pdev->dev);
> +
> +	tegra_gmi_disable(priv);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id tegra_gmi_id_table[] = {
> +	{ .compatible = "nvidia,tegra20-gmi", },
> +	{ .compatible = "nvidia,tegra30-gmi", },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, tegra_gmi_id_table);
> +
> +static struct platform_driver tegra_gmi_driver = {
> +	.probe = tegra_gmi_probe,
> +	.remove = tegra_gmi_remove,
> +	.driver = {
> +		.name		= "tegra-gmi",
> +		.of_match_table	= tegra_gmi_id_table,
> +	},
> +};
> +module_platform_driver(tegra_gmi_driver);
> +
> +MODULE_AUTHOR("Mirza Krak <mirza.krak@gmail.com");
> +MODULE_DESCRIPTION("NVIDIA Tegra GMI Bus Driver");
> +MODULE_LICENSE("GPL v2");
> --
> 2.1.4
>

Cheers
Jon

-- 
nvpublic