Subject: [RFC v2] ARM: memory: da8xx-ddrctl: new driver

From: [email-masked] (Kevin Hilman)
Date: Tue, 25 Oct 2016 10:57:37 -0700

Bartosz Golaszewski <[email-masked]> writes:

> Create a new driver for the da8xx DDR2/mDDR controller and implement
> support for writing to the Peripheral Bus Burst Priority Register.
>
> Signed-off-by: Bartosz Golaszewski <[email-masked]>
> ---
>  .../memory-controllers/ti-da8xx-ddrctl.txt         |  20 +++
>  drivers/memory/Kconfig                             |   8 +
>  drivers/memory/Makefile                            |   1 +
>  drivers/memory/da8xx-ddrctl.c                      | 175 +++++++++++++++++++++
>  4 files changed, 204 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/memory-controllers/ti-da8xx-ddrctl.txt
>  create mode 100644 drivers/memory/da8xx-ddrctl.c
>
> diff --git a/Documentation/devicetree/bindings/memory-controllers/ti-da8xx-ddrctl.txt b/Documentation/devicetree/bindings/memory-controllers/ti-da8xx-ddrctl.txt
> new file mode 100644
> index 0000000..7e271dd
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/memory-controllers/ti-da8xx-ddrctl.txt
> @@ -0,0 +1,20 @@
> +* Device tree bindings for Texas Instruments da8xx DDR2/mDDR memory controller
> +
> +The DDR2/mDDR memory controller present on Texas Instruments da8xx SoCs features
> +a set of registers which allow to tweak the controller's behavior.
> +
> +Documentation:
> +OMAP-L138 (DA850) - http://www.ti.com/lit/ug/spruh82c/spruh82c.pdf
> +
> +Required properties:
> +
> +- compatible:		"ti,da850-ddr-controller" - for da850 SoC based boards
> +- reg:			a tuple containing the base address of the memory
> +			controller and the size of the memory area to map
> +
> +Example for da850 shown below.
> +
> +ddrctl {
> +	compatible = "ti,da850-ddr-controller";
> +	reg = <0xB0000000 0x100>;
> +};

Axel's series for the USB PHY reminded me that the PHY also has some
config registers in this same area, and his series creates a syscon for
a similar range of registers.

Could you create a syscon for the SYSCFG0 registers, which would then
be used by ths driver and your other drivers/bus driver?  Then the
binding  would just reference the sysconf via phandle, and your driver
can use syscon_regmap_lookup_by_phandle()

> diff --git a/drivers/memory/Kconfig b/drivers/memory/Kconfig
> index 4b4c0c3..ec80e35 100644
> --- a/drivers/memory/Kconfig
> +++ b/drivers/memory/Kconfig
> @@ -134,6 +134,14 @@ config MTK_SMI
>  	  mainly help enable/disable iommu and control the power domain and
>  	  clocks for each local arbiter.
>  
> +config DA8XX_DDRCTL
> +	bool "Texas Instruments da8xx DDR2/mDDR driver"
> +	depends on ARCH_DAVINCI_DA8XX
> +	help
> +	  This driver is for the DDR2/mDDR Memory Controller present on
> +	  Texas Instruments da8xx SoCs. It's used to tweak various memory
> +	  controller configuration options.
> +
>  source "drivers/memory/samsung/Kconfig"
>  source "drivers/memory/tegra/Kconfig"
>  
> diff --git a/drivers/memory/Makefile b/drivers/memory/Makefile
> index b20ae38..e88097fb 100644
> --- a/drivers/memory/Makefile
> +++ b/drivers/memory/Makefile
> @@ -17,6 +17,7 @@ obj-$(CONFIG_MVEBU_DEVBUS)	+= mvebu-devbus.o
>  obj-$(CONFIG_TEGRA20_MC)	+= tegra20-mc.o
>  obj-$(CONFIG_JZ4780_NEMC)	+= jz4780-nemc.o
>  obj-$(CONFIG_MTK_SMI)		+= mtk-smi.o
> +obj-$(CONFIG_DA8XX_DDRCTL)	+= da8xx-ddrctl.o
>  
>  obj-$(CONFIG_SAMSUNG_MC)	+= samsung/
>  obj-$(CONFIG_TEGRA_MC)		+= tegra/
> diff --git a/drivers/memory/da8xx-ddrctl.c b/drivers/memory/da8xx-ddrctl.c
> new file mode 100644
> index 0000000..66022df
> --- /dev/null
> +++ b/drivers/memory/da8xx-ddrctl.c
> @@ -0,0 +1,175 @@
> +/*
> + * TI da8xx DDR2/mDDR controller driver
> + *
> + * Copyright (C) 2016 BayLibre SAS
> + *
> + * Author:
> + *   Bartosz Golaszewski <[email-masked]>
> + *
> + * 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/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/of_fdt.h>
> +#include <linux/platform_device.h>
> +#include <linux/io.h>
> +
> +/*
> + * REVISIT: Linux doesn't have a good framework for the kind of performance
> + * knobs this driver controls. We can't use device tree properties as it deals
> + * with hardware configuration rather than description. We also don't want to
> + * commit to maintaining some random sysfs attributes.
> + *
> + * For now we just hardcode the register values for the boards that need
> + * some changes (as is the case for the LCD controller on da850-lcdk - the
> + * first board we support here). When linux gets an appropriate framework,
> + * we'll easily convert the driver to it.
> + */
> +
> +struct da8xx_ddrctl_config_knob {
> +	const char *name;
> +	u32 reg;
> +	u32 mask;
> +	u32 offset;

nit: call this shift instead, which will also map well onto the regmap
accessors (which you'll use when switching to syscon.)

> +};
> +
> +static const struct da8xx_ddrctl_config_knob da8xx_ddrctl_knobs[] = {
> +	{
> +		.name = "da850-pbbpr",
> +		.reg = 0x20,
> +		.mask = 0xffffff00,
> +		.offset = 0,
> +	},
> +};
> +
> +struct da8xx_ddrctl_setting {
> +	const char *name;
> +	u32 val;
> +};
> +
> +struct da8xx_ddrctl_board_settings {
> +	const char *board;
> +	const struct da8xx_ddrctl_setting *settings;
> +};
> +
> +static const struct da8xx_ddrctl_setting da850_lcdk_ddrctl_settings[] = {
> +	{
> +		.name = "da850-pbbpr",
> +		.val = 0x20,
> +	},
> +	{ }
> +};
> +
> +static const struct da8xx_ddrctl_board_settings da8xx_ddrctl_board_confs[] = {
> +	{
> +		.board = "ti,da850-lcdk",
> +		.settings = da850_lcdk_ddrctl_settings,
> +	},
> +};
> +
> +static const struct da8xx_ddrctl_config_knob *
> +da8xx_ddrctl_match_knob(const struct da8xx_ddrctl_setting *setting)
> +{
> +	const struct da8xx_ddrctl_config_knob *knob;
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(da8xx_ddrctl_knobs); i++) {
> +		knob = &da8xx_ddrctl_knobs[i];
> +
> +		if (strcmp(knob->name, setting->name) == 0)
> +			return knob;
> +	}
> +
> +	return NULL;
> +}
> +
> +static const struct da8xx_ddrctl_setting *da8xx_ddrctl_get_board_settings(void)
> +{
> +	const struct da8xx_ddrctl_board_settings *board_settings;
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(da8xx_ddrctl_board_confs); i++) {
> +		board_settings = &da8xx_ddrctl_board_confs[0];

Looks like that '0' should be 'i' ?

> +		if (of_machine_is_compatible(board_settings->board))
> +			return board_settings->settings;
> +	}
> +
> +	return NULL;
> +}
> +
> +static int da8xx_ddrctl_probe(struct platform_device *pdev)
> +{
> +	const struct da8xx_ddrctl_config_knob *knob;
> +	const struct da8xx_ddrctl_setting *setting;
> +	struct device_node *node;
> +	struct resource *res;
> +	void __iomem *ddrctl;
> +	struct device *dev;
> +	u32 reg;
> +
> +	dev = &pdev->dev;
> +	node = dev->of_node;
> +
> +	setting = da8xx_ddrctl_get_board_settings();
> +	if (!setting) {
> +		dev_err(dev, "no settings for board '%s'\n",
> +			of_flat_dt_get_machine_name());
> +		return -EINVAL;
> +	}
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	ddrctl = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(ddrctl)) {
> +		dev_err(dev, "unable to map memory controller registers\n");
> +		return PTR_ERR(ddrctl);
> +	}
> +
> +	for (; setting->name; setting++) {
> +		knob = da8xx_ddrctl_match_knob(setting);
> +		if (!knob) {
> +			dev_warn(dev,
> +				 "no such config option: %s\n", setting->name);
> +			continue;
> +		}
> +
> +		if (knob->reg > (res->end - res->start - sizeof(u32))) {
> +			dev_warn(dev,
> +				 "register offset of '%s' exceeds mapped memory size\n",
> +				 knob->name);
> +			continue;
> +		}
> +
> +		reg = __raw_readl(ddrctl + knob->reg);
> +		reg &= knob->mask;
> +		reg |= setting->val << knob->offset;
> +
> +		dev_dbg(dev, "writing 0x%08x to %s\n", reg, setting->name);
> +
> +		__raw_writel(reg, ddrctl + knob->reg);

nit: I don't think you need the __raw accessors here.

But in any case, moving to syscon you'll be using regmap accessors, and
this can just be converted to a single regmap_update_bits.

Kevin

> +	}
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id da8xx_ddrctl_of_match[] = {
> +	{ .compatible = "ti,da850-ddr-controller", },
> +	{ },
> +};
> +
> +static struct platform_driver da8xx_ddrctl_driver = {
> +	.probe = da8xx_ddrctl_probe,
> +	.driver = {
> +		.name = "da850-ddr-controller",
> +		.of_match_table = da8xx_ddrctl_of_match,
> +	},
> +};
> +module_platform_driver(da8xx_ddrctl_driver);
> +
> +MODULE_AUTHOR("Bartosz Golaszewski <[email-masked]>");
> +MODULE_DESCRIPTION("TI da8xx DDR2/mDDR controller driver");
> +MODULE_LICENSE("GPL v2");