memory: dfl-emif: add the DFL EMIF private feature driver

This driver is for the EMIF private feature implemented under FPGA
Device Feature List (DFL) framework. It is used to expose memory
interface status information as well as memory clearing control.

The purpose of memory clearing block is to zero out all private memory
when FPGA is to be reprogrammed. This gives users a reliable method to
prevent potential data leakage.

[mdf@kernel.org: Fixed up ABI doc]

Reviewed-by: Tom Rix <trix@redhat.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Xu Yilun <yilun.xu@intel.com>
Signed-off-by: Russ Weight <russell.h.weight@intel.com>
Link: https://lore.kernel.org/r/20210107043714.991646-9-mdf@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-bus-dfl-devices-emif

@@ -0,0 +1,25 @@
+What:		/sys/bus/dfl/devices/dfl_dev.X/infX_cal_fail
+Date:		Oct 2020
+KernelVersion:	5.12
+Contact:	Xu Yilun <yilun.xu@intel.com>
+Description:	Read-only. It indicates if the calibration failed on this
+		memory interface. "1" for calibration failure, "0" for OK.
+		Format: %u
+
+What:		/sys/bus/dfl/devices/dfl_dev.X/infX_init_done
+Date:		Oct 2020
+KernelVersion:	5.12
+Contact:	Xu Yilun <yilun.xu@intel.com>
+Description:	Read-only. It indicates if the initialization completed on
+		this memory interface. "1" for initialization complete, "0"
+		for not yet.
+		Format: %u
+
+What:		/sys/bus/dfl/devices/dfl_dev.X/infX_clear
+Date:		Oct 2020
+KernelVersion:	5.12
+Contact:	Xu Yilun <yilun.xu@intel.com>
+Description:	Write-only. Writing "1" to this file will zero out all memory
+		data in this memory interface. Writing of other values is
+		invalid.
+		Format: %u

drivers/memory/Kconfig

@@ -137,6 +137,15 @@ config TI_EMIF_SRAM
 	  sequence so this driver provides several relocatable PM functions
 	  for the SoC PM code to use.
 
+config FPGA_DFL_EMIF
+	tristate "FPGA DFL EMIF Driver"
+	depends on FPGA_DFL && HAS_IOMEM
+	help
+	  This driver is for the EMIF private feature implemented under
+	  FPGA Device Feature List (DFL) framework. It is used to expose
+	  memory interface status information as well as memory clearing
+	  control.
+
 config MVEBU_DEVBUS
 	bool "Marvell EBU Device Bus Controller"
 	default y if PLAT_ORION

drivers/memory/Makefile

@@ -28,6 +28,8 @@ obj-$(CONFIG_STM32_FMC2_EBI)	+= stm32-fmc2-ebi.o
 obj-$(CONFIG_SAMSUNG_MC)	+= samsung/
 obj-$(CONFIG_TEGRA_MC)		+= tegra/
 obj-$(CONFIG_TI_EMIF_SRAM)	+= ti-emif-sram.o
+obj-$(CONFIG_FPGA_DFL_EMIF)	+= dfl-emif.o
+
 ti-emif-sram-objs		:= ti-emif-pm.o ti-emif-sram-pm.o
 
 AFLAGS_ti-emif-sram-pm.o	:=-Wa,-march=armv7-a

drivers/memory/dfl-emif.c

@@ -0,0 +1,207 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DFL device driver for EMIF private feature
+ *
+ * Copyright (C) 2020 Intel Corporation, Inc.
+ *
+ */
+#include <linux/bitfield.h>
+#include <linux/dfl.h>
+#include <linux/errno.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/io-64-nonatomic-lo-hi.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+
+#define FME_FEATURE_ID_EMIF		0x9
+
+#define EMIF_STAT			0x8
+#define EMIF_STAT_INIT_DONE_SFT		0
+#define EMIF_STAT_CALC_FAIL_SFT		8
+#define EMIF_STAT_CLEAR_BUSY_SFT	16
+#define EMIF_CTRL			0x10
+#define EMIF_CTRL_CLEAR_EN_SFT		0
+#define EMIF_CTRL_CLEAR_EN_MSK		GENMASK_ULL(3, 0)
+
+#define EMIF_POLL_INVL			10000 /* us */
+#define EMIF_POLL_TIMEOUT		5000000 /* us */
+
+struct dfl_emif {
+	struct device *dev;
+	void __iomem *base;
+	spinlock_t lock;	/* Serialises access to EMIF_CTRL reg */
+};
+
+struct emif_attr {
+	struct device_attribute attr;
+	u32 shift;
+	u32 index;
+};
+
+#define to_emif_attr(dev_attr) \
+	container_of(dev_attr, struct emif_attr, attr)
+
+static ssize_t emif_state_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct emif_attr *eattr = to_emif_attr(attr);
+	struct dfl_emif *de = dev_get_drvdata(dev);
+	u64 val;
+
+	val = readq(de->base + EMIF_STAT);
+
+	return sysfs_emit(buf, "%u\n",
+			  !!(val & BIT_ULL(eattr->shift + eattr->index)));
+}
+
+static ssize_t emif_clear_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	struct emif_attr *eattr = to_emif_attr(attr);
+	struct dfl_emif *de = dev_get_drvdata(dev);
+	u64 clear_busy_msk, clear_en_msk, val;
+	void __iomem *base = de->base;
+
+	if (!sysfs_streq(buf, "1"))
+		return -EINVAL;
+
+	clear_busy_msk = BIT_ULL(EMIF_STAT_CLEAR_BUSY_SFT + eattr->index);
+	clear_en_msk = BIT_ULL(EMIF_CTRL_CLEAR_EN_SFT + eattr->index);
+
+	spin_lock(&de->lock);
+	/* The CLEAR_EN field is WO, but other fields are RW */
+	val = readq(base + EMIF_CTRL);
+	val &= ~EMIF_CTRL_CLEAR_EN_MSK;
+	val |= clear_en_msk;
+	writeq(val, base + EMIF_CTRL);
+	spin_unlock(&de->lock);
+
+	if (readq_poll_timeout(base + EMIF_STAT, val,
+			       !(val & clear_busy_msk),
+			       EMIF_POLL_INVL, EMIF_POLL_TIMEOUT)) {
+		dev_err(de->dev, "timeout, fail to clear\n");
+		return -ETIMEDOUT;
+	}
+
+	return count;
+}
+
+#define emif_state_attr(_name, _shift, _index)				\
+	static struct emif_attr emif_attr_##inf##_index##_##_name =	\
+		{ .attr = __ATTR(inf##_index##_##_name, 0444,		\
+				 emif_state_show, NULL),		\
+		  .shift = (_shift), .index = (_index) }
+
+#define emif_clear_attr(_index)						\
+	static struct emif_attr emif_attr_##inf##_index##_clear =	\
+		{ .attr = __ATTR(inf##_index##_clear, 0200,		\
+				 NULL, emif_clear_store),		\
+		  .index = (_index) }
+
+emif_state_attr(init_done, EMIF_STAT_INIT_DONE_SFT, 0);
+emif_state_attr(init_done, EMIF_STAT_INIT_DONE_SFT, 1);
+emif_state_attr(init_done, EMIF_STAT_INIT_DONE_SFT, 2);
+emif_state_attr(init_done, EMIF_STAT_INIT_DONE_SFT, 3);
+
+emif_state_attr(cal_fail, EMIF_STAT_CALC_FAIL_SFT, 0);
+emif_state_attr(cal_fail, EMIF_STAT_CALC_FAIL_SFT, 1);
+emif_state_attr(cal_fail, EMIF_STAT_CALC_FAIL_SFT, 2);
+emif_state_attr(cal_fail, EMIF_STAT_CALC_FAIL_SFT, 3);
+
+emif_clear_attr(0);
+emif_clear_attr(1);
+emif_clear_attr(2);
+emif_clear_attr(3);
+
+static struct attribute *dfl_emif_attrs[] = {
+	&emif_attr_inf0_init_done.attr.attr,
+	&emif_attr_inf0_cal_fail.attr.attr,
+	&emif_attr_inf0_clear.attr.attr,
+
+	&emif_attr_inf1_init_done.attr.attr,
+	&emif_attr_inf1_cal_fail.attr.attr,
+	&emif_attr_inf1_clear.attr.attr,
+
+	&emif_attr_inf2_init_done.attr.attr,
+	&emif_attr_inf2_cal_fail.attr.attr,
+	&emif_attr_inf2_clear.attr.attr,
+
+	&emif_attr_inf3_init_done.attr.attr,
+	&emif_attr_inf3_cal_fail.attr.attr,
+	&emif_attr_inf3_clear.attr.attr,
+
+	NULL,
+};
+
+static umode_t dfl_emif_visible(struct kobject *kobj,
+				struct attribute *attr, int n)
+{
+	struct dfl_emif *de = dev_get_drvdata(kobj_to_dev(kobj));
+	struct emif_attr *eattr = container_of(attr, struct emif_attr,
+					       attr.attr);
+	u64 val;
+
+	/*
+	 * This device supports upto 4 memory interfaces, but not all
+	 * interfaces are used on different platforms. The read out value of
+	 * CLEAN_EN field (which is a bitmap) could tell how many interfaces
+	 * are available.
+	 */
+	val = FIELD_GET(EMIF_CTRL_CLEAR_EN_MSK, readq(de->base + EMIF_CTRL));
+
+	return (val & BIT_ULL(eattr->index)) ? attr->mode : 0;
+}
+
+static const struct attribute_group dfl_emif_group = {
+	.is_visible = dfl_emif_visible,
+	.attrs = dfl_emif_attrs,
+};
+
+static const struct attribute_group *dfl_emif_groups[] = {
+	&dfl_emif_group,
+	NULL,
+};
+
+static int dfl_emif_probe(struct dfl_device *ddev)
+{
+	struct device *dev = &ddev->dev;
+	struct dfl_emif *de;
+
+	de = devm_kzalloc(dev, sizeof(*de), GFP_KERNEL);
+	if (!de)
+		return -ENOMEM;
+
+	de->base = devm_ioremap_resource(dev, &ddev->mmio_res);
+	if (IS_ERR(de->base))
+		return PTR_ERR(de->base);
+
+	de->dev = dev;
+	spin_lock_init(&de->lock);
+	dev_set_drvdata(dev, de);
+
+	return 0;
+}
+
+static const struct dfl_device_id dfl_emif_ids[] = {
+	{ FME_ID, FME_FEATURE_ID_EMIF },
+	{ }
+};
+MODULE_DEVICE_TABLE(dfl, dfl_emif_ids);
+
+static struct dfl_driver dfl_emif_driver = {
+	.drv	= {
+		.name       = "dfl-emif",
+		.dev_groups = dfl_emif_groups,
+	},
+	.id_table = dfl_emif_ids,
+	.probe   = dfl_emif_probe,
+};
+module_dfl_driver(dfl_emif_driver);
+
+MODULE_DESCRIPTION("DFL EMIF driver");
+MODULE_AUTHOR("Intel Corporation");
+MODULE_LICENSE("GPL v2");