Date:   Fri, 22 Jul 2022 21:31:43 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Florian Fainelli <f.fainelli@...il.com>,
        linux-kernel@...r.kernel.org
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "moderated list:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 3/3] memory: Add Broadcom STB memory controller driver

On 22/07/2022 20:41, Florian Fainelli wrote:
> Add support for configuring the Self Refresh Power Down (SRPD)
> inactivity timeout on Broadcom STB chips. This is used to conserve power
> when the DRAM activity is reduced.
> 
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  drivers/memory/Kconfig        |   9 +
>  drivers/memory/Makefile       |   1 +
>  drivers/memory/brcmstb_memc.c | 304 ++++++++++++++++++++++++++++++++++
>  3 files changed, 314 insertions(+)
>  create mode 100644 drivers/memory/brcmstb_memc.c
> 
> diff --git a/drivers/memory/Kconfig b/drivers/memory/Kconfig
> index ac1a411648d8..fac290e48e0b 100644
> --- a/drivers/memory/Kconfig
> +++ b/drivers/memory/Kconfig
> @@ -66,6 +66,15 @@ config BRCMSTB_DPFE
>  	  for the DRAM's temperature. Slower refresh rate means cooler RAM,
>  	  higher refresh rate means hotter RAM.
>  
> +config BRCMSTB_MEMC
> +	tristate "Broadcom STB MEMC driver"
> +	default ARCH_BRCMSTB
> +	depends on ARCH_BRCMSTB || COMPILE_TEST
> +	help
> +	  This driver provides a way to configure the Broadcom STB memory
> +	  controller and specifically control the Self Refresh Power Down
> +	  (SRPD) inactivity timeout.
> +
>  config BT1_L2_CTL
>  	bool "Baikal-T1 CM2 L2-RAM Cache Control Block"
>  	depends on MIPS_BAIKAL_T1 || COMPILE_TEST
> diff --git a/drivers/memory/Makefile b/drivers/memory/Makefile
> index bc7663ed1c25..e148f636c082 100644
> --- a/drivers/memory/Makefile
> +++ b/drivers/memory/Makefile
> @@ -11,6 +11,7 @@ obj-$(CONFIG_ARM_PL172_MPMC)	+= pl172.o
>  obj-$(CONFIG_ATMEL_SDRAMC)	+= atmel-sdramc.o
>  obj-$(CONFIG_ATMEL_EBI)		+= atmel-ebi.o
>  obj-$(CONFIG_BRCMSTB_DPFE)	+= brcmstb_dpfe.o
> +obj-$(CONFIG_BRCMSTB_MEMC)	+= brcmstb_memc.o
>  obj-$(CONFIG_BT1_L2_CTL)	+= bt1-l2-ctl.o
>  obj-$(CONFIG_TI_AEMIF)		+= ti-aemif.o
>  obj-$(CONFIG_TI_EMIF)		+= emif.o
> diff --git a/drivers/memory/brcmstb_memc.c b/drivers/memory/brcmstb_memc.c
> new file mode 100644
> index 000000000000..881da958c542
> --- /dev/null
> +++ b/drivers/memory/brcmstb_memc.c
> @@ -0,0 +1,304 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * DDR Self-Refresh Power Down (SRPD) support for Broadcom STB SoCs
> + *
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/platform_device.h>
> +#include <linux/of_device.h>
> +#include <linux/io.h>

Let's order the includes by name. It reduces the chances of conflicts later.

> +
> +#define REG_MEMC_CNTRLR_CONFIG		0x00
> +#define  CNTRLR_CONFIG_LPDDR4		5

This is also a SHIFT? Later you use such suffix.

> +#define  CNTRLR_CONFIG_MASK		0xf
> +#define REG_MEMC_SRPD_CFG_21		0x20
> +#define REG_MEMC_SRPD_CFG_20		0x34
> +#define REG_MEMC_SRPD_CFG_1x		0x3c
> +#define INACT_COUNT_SHIFT		0
> +#define INACT_COUNT_MASK		0xffff
> +#define SRPD_EN_SHIFT			16
> +
> +struct brcmstb_memc_data {
> +	u32 srpd_offset;
> +};
> +
> +struct brcmstb_memc {
> +	struct device *dev;
> +	void __iomem *ddr_ctrl;
> +	unsigned int timeout_cycles;
> +	u32 frequency;
> +	u32 srpd_offset;
> +};
> +
> +static int brcmstb_memc_uses_lpddr4(struct brcmstb_memc *memc)
> +{
> +	void __iomem *config = memc->ddr_ctrl + REG_MEMC_CNTRLR_CONFIG;
> +	u32 reg;
> +
> +	reg = readl_relaxed(config) & CNTRLR_CONFIG_MASK;
> +
> +	return reg == CNTRLR_CONFIG_LPDDR4;
> +}
> +
> +static int brcmstb_memc_srpd_config(struct brcmstb_memc *memc,
> +				    unsigned int cycles)
> +{
> +	void __iomem *cfg = memc->ddr_ctrl + memc->srpd_offset;
> +	u32 val;
> +
> +	/* Max timeout supported in HW */
> +	if (cycles > INACT_COUNT_MASK)
> +		return -EINVAL;
> +
> +	memc->timeout_cycles = cycles;
> +
> +	val = (cycles << INACT_COUNT_SHIFT) & INACT_COUNT_MASK;
> +	if (cycles)
> +		val |= (1 << SRPD_EN_SHIFT);

BIT(SRPD_EN_SHIFT)

> +
> +	writel_relaxed(val, cfg);
> +	(void)readl_relaxed(cfg);

Leave a comment why do you need such read.

> +
> +	return 0;
> +}
> +
> +static ssize_t frequency_show(struct device *dev,
> +			      struct device_attribute *attr, char *buf)
> +{
> +	struct brcmstb_memc *memc = dev_get_drvdata(dev);
> +
> +	return sprintf(buf, "%d\n", memc->frequency);
> +}
> +
> +static ssize_t srpd_show(struct device *dev,
> +			 struct device_attribute *attr, char *buf)
> +{
> +	struct brcmstb_memc *memc = dev_get_drvdata(dev);
> +
> +	return sprintf(buf, "%d\n", memc->timeout_cycles);
> +}
> +
> +static ssize_t srpd_store(struct device *dev, struct device_attribute *attr,
> +			  const char *buf, size_t count)

You need to document the sysfs ABI.

> +{
> +	struct brcmstb_memc *memc = dev_get_drvdata(dev);
> +	unsigned int val;
> +	int ret;
> +

Start with /*

> +	/* Cannot change the inactivity timeout on LPDDR4 chips because the

...for this comment.

> +	 * dynamic tuning process will also get affected by the inactivity
> +	 * timeout, thus making it non functional.
> +	 */
> +	if (brcmstb_memc_uses_lpddr4(memc))
> +		return -EOPNOTSUPP;
> +
> +	ret = kstrtouint(buf, 10, &val);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = brcmstb_memc_srpd_config(memc, val);
> +	if (ret)
> +		return ret;
> +
> +	return count;
> +}
> +
> +static DEVICE_ATTR_RO(frequency);
> +static DEVICE_ATTR_RW(srpd);
> +
> +static struct attribute *dev_attrs[] = {
> +	&dev_attr_frequency.attr,
> +	&dev_attr_srpd.attr,
> +	NULL,
> +};
> +
> +static struct attribute_group dev_attr_group = {
> +	.attrs = dev_attrs,
> +};
> +
> +static const struct of_device_id brcmstb_memc_of_match[];
> +
> +static int brcmstb_memc_probe(struct platform_device *pdev)
> +{
> +	const struct brcmstb_memc_data *memc_data;> +	const struct of_device_id *of_id;
> +	struct device *dev = &pdev->dev;
> +	struct brcmstb_memc *memc;
> +	struct resource *res;
> +	int ret;
> +
> +	memc = devm_kzalloc(dev, sizeof(*memc), GFP_KERNEL);
> +	if (!memc)
> +		return -ENOMEM;
> +
> +	dev_set_drvdata(dev, memc);
> +
> +	of_id = of_match_device(brcmstb_memc_of_match, dev);
> +	if (!of_id || !of_id->data)

!of_id is not possible
!of_id->data is the same not possible (or even less...)

I would suggest to drop both or at least the latter.

> +		return -EINVAL;
> +
> +	memc_data = of_id->data;
> +	memc->srpd_offset = memc_data->srpd_offset;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	memc->ddr_ctrl = devm_ioremap_resource(dev, res);

devm_platform_ioremap_resource()

> +	if (IS_ERR(memc->ddr_ctrl))
> +		return PTR_ERR(memc->ddr_ctrl);
> +
> +	of_property_read_u32(pdev->dev.of_node, "clock-frequency",
> +			     &memc->frequency);

Undocumented property.

> +
> +	ret = sysfs_create_group(&dev->kobj, &dev_attr_group);
> +	if (ret) {
> +		dev_err(dev, "failed to create attribute group (%d)\n", ret);

I am pretty sure there was a helper to make it simpler, but canno recall
now...

> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int brcmstb_memc_remove(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +
> +	sysfs_remove_group(&dev->kobj, &dev_attr_group);
> +
> +	return 0;
> +}
> +
> +enum brcmstb_memc_hwtype {
> +	BRCMSTB_MEMC_V21,
> +	BRCMSTB_MEMC_V20,
> +	BRCMSTB_MEMC_V1X,
> +};
> +
> +static const struct brcmstb_memc_data brcmstb_memc_versions[] = {
> +	{ .srpd_offset = REG_MEMC_SRPD_CFG_21 },
> +	{ .srpd_offset = REG_MEMC_SRPD_CFG_20 },
> +	{ .srpd_offset = REG_MEMC_SRPD_CFG_1x },
> +};
> +
> +static const struct of_device_id brcmstb_memc_of_match[] = {
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-b.1.x",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V1X]
> +	},
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-b.2.0",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V20]
> +	},
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-b.2.1",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V21]
> +	},
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-b.2.2",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V21]
> +	},
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-b.2.3",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V21]
> +	},
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-b.2.5",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V21]
> +	},
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-b.2.6",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V21]
> +	},
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-b.2.7",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V21]
> +	},
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-b.2.8",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V21]
> +	},
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-b.3.0",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V21]
> +	},
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-b.3.1",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V21]
> +	},
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-c.1.0",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V21]
> +	},
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-c.1.1",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V21]
> +	},
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-c.1.2",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V21]
> +	},
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-c.1.3",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V21]
> +	},
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr-rev-c.1.4",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V21]
> +	},
> +	/* default to the original offset */
> +	{
> +		.compatible = "brcm,brcmstb-memc-ddr",
> +		.data = &brcmstb_memc_versions[BRCMSTB_MEMC_V1X]
> +	},
> +	{}
> +};
> +
> +static int __maybe_unused brcmstb_memc_suspend(struct device *dev)
> +{
> +	struct brcmstb_memc *memc = dev_get_drvdata(dev);
> +	void __iomem *cfg = memc->ddr_ctrl + memc->srpd_offset;
> +	u32 val;
> +
> +	if (memc->timeout_cycles == 0)
> +		return 0;
> +
> +	/* Disable SPRD prior to suspending the system since that can

SRPD?

Comment starts with /* alone


> +	 * cause issues with e.g: XPT_DMA trying to hash memory
> +	 */
> +	val = readl_relaxed(cfg);
> +	val &= ~(1 << SRPD_EN_SHIFT);

~(BIT(SRPD_EN_SHIFT))

> +	writel_relaxed(val, cfg);
> +	(void)readl_relaxed(cfg);
> +
> +	return 0;
> +}
> +
> +static int __maybe_unused brcmstb_memc_resume(struct device *dev)
> +{
> +	struct brcmstb_memc *memc = dev_get_drvdata(dev);
> +
> +	if (memc->timeout_cycles == 0)
> +		return 0;
> +
> +	return brcmstb_memc_srpd_config(memc, memc->timeout_cycles);
> +}
> +
> +static SIMPLE_DEV_PM_OPS(brcmstb_memc_pm_ops, brcmstb_memc_suspend,
> +			 brcmstb_memc_resume);
> +
> +static struct platform_driver brcmstb_memc_driver = {
> +	.probe = brcmstb_memc_probe,
> +	.remove = brcmstb_memc_remove,
> +	.driver = {
> +		.name		= "brcmstb_memc",
> +		.owner		= THIS_MODULE,
> +		.of_match_table	= of_match_ptr(brcmstb_memc_of_match),

This does not match brcmstb_memc_of_match - you will have unused
variable warning. Drop of_match_ptr or add maybe_unused.



Best regards,
Krzysztof

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