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Date: Sat, 16 May 2020 18:12:29 +0800
From: Baolin Wang <baolin.wang7@...il.com>
To: lee.jones@...aro.org, arnd@...db.de
Cc: broonie@...nel.org, baolin.wang7@...il.com, orsonzhai@...il.com,
zhang.lyra@...il.com, linux-kernel@...r.kernel.org
Subject: [PATCH v4 2/2] soc: sprd: Add Spreadtrum special bits updating support
The spreadtrum platform uses a special set/clear method to update
registers' bits, which can remove the race of updating the global
registers between the multiple subsystems. Thus we can register
a physical regmap bus into syscon core to support this.
Signed-off-by: Baolin Wang <baolin.wang7@...il.com>
---
drivers/soc/Kconfig | 1 +
drivers/soc/Makefile | 1 +
drivers/soc/sprd/Kconfig | 16 +++++++
drivers/soc/sprd/Makefile | 2 +
drivers/soc/sprd/sprd_syscon.c | 86 ++++++++++++++++++++++++++++++++++
5 files changed, 106 insertions(+)
create mode 100644 drivers/soc/sprd/Kconfig
create mode 100644 drivers/soc/sprd/Makefile
create mode 100644 drivers/soc/sprd/sprd_syscon.c
diff --git a/drivers/soc/Kconfig b/drivers/soc/Kconfig
index 425ab6f7e375..8cfbf2dc518d 100644
--- a/drivers/soc/Kconfig
+++ b/drivers/soc/Kconfig
@@ -23,5 +23,6 @@ source "drivers/soc/versatile/Kconfig"
source "drivers/soc/xilinx/Kconfig"
source "drivers/soc/zte/Kconfig"
source "drivers/soc/kendryte/Kconfig"
+source "drivers/soc/sprd/Kconfig"
endmenu
diff --git a/drivers/soc/Makefile b/drivers/soc/Makefile
index 36452bed86ef..7d156a6dd536 100644
--- a/drivers/soc/Makefile
+++ b/drivers/soc/Makefile
@@ -29,3 +29,4 @@ obj-$(CONFIG_PLAT_VERSATILE) += versatile/
obj-y += xilinx/
obj-$(CONFIG_ARCH_ZX) += zte/
obj-$(CONFIG_SOC_KENDRYTE) += kendryte/
+obj-$(CONFIG_ARCH_SPRD) += sprd/
diff --git a/drivers/soc/sprd/Kconfig b/drivers/soc/sprd/Kconfig
new file mode 100644
index 000000000000..38d1f5971a28
--- /dev/null
+++ b/drivers/soc/sprd/Kconfig
@@ -0,0 +1,16 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# SPRD SoC drivers
+#
+
+menu "Spreadtrum SoC drivers"
+ depends on ARCH_SPRD || COMPILE_TEST
+
+config SPRD_SYSCON
+ tristate "Spreadtrum syscon support"
+ depends on ARCH_SPRD || COMPILE_TEST
+ help
+ Say yes here to add support for the Spreadtrum syscon driver,
+ which is used to implement the atomic method of bits updating.
+
+endmenu
diff --git a/drivers/soc/sprd/Makefile b/drivers/soc/sprd/Makefile
new file mode 100644
index 000000000000..4d7715553cf6
--- /dev/null
+++ b/drivers/soc/sprd/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_SPRD_SYSCON) += sprd_syscon.o
diff --git a/drivers/soc/sprd/sprd_syscon.c b/drivers/soc/sprd/sprd_syscon.c
new file mode 100644
index 000000000000..cdc326ef94e5
--- /dev/null
+++ b/drivers/soc/sprd/sprd_syscon.c
@@ -0,0 +1,86 @@
+//SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Spreadtrum Communications Inc.
+ */
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+
+#define SPRD_REG_SET_OFFSET 0x1000
+#define SPRD_REG_CLR_OFFSET 0x2000
+
+/*
+ * The Spreadtrum platform defines a special set/clear method to update
+ * registers' bits, which means it can write values to the register's SET
+ * address (offset is 0x1000) to set bits, and write values to the register's
+ * CLEAR address (offset is 0x2000) to clear bits.
+ *
+ * This set/clear method can help to remove the race of accessing the global
+ * registers between the multiple subsystems instead of using hardware
+ * spinlocks.
+ *
+ * Note: there is a potential risk when users want to set and clear bits
+ * at the same time, since the set/clear method will always do bits setting
+ * before bits clearing, which may cause some unexpected results if the
+ * operation sequence is strict. Thus we recommend that do not set and
+ * clear bits at the same time if you are not sure about the results.
+ */
+static int sprd_syscon_update_bits(void *context, unsigned int reg,
+ unsigned int mask, unsigned int val)
+{
+ void __iomem *base = context;
+ unsigned int set, clr;
+
+ set = val & mask;
+ clr = ~set & mask;
+
+ if (set)
+ writel(set, base + reg + SPRD_REG_SET_OFFSET);
+
+ if (clr)
+ writel(clr, base + reg + SPRD_REG_CLR_OFFSET);
+
+ WARN_ONCE(set && clr, "%s: non-atomic update", __func__);
+ return 0;
+}
+
+static int sprd_syscon_read(void *context, unsigned int reg, unsigned int *val)
+{
+ void __iomem *base = context;
+
+ *val = readl(base + reg);
+ return 0;
+}
+
+static int sprd_syscon_write(void *context, unsigned int reg, unsigned int val)
+{
+ void __iomem *base = context;
+
+ writel(val, base + reg);
+ return 0;
+}
+
+static struct regmap_bus sprd_syscon_regmap = {
+ .fast_io = true,
+ .reg_write = sprd_syscon_write,
+ .reg_read = sprd_syscon_read,
+ .reg_update_bits = sprd_syscon_update_bits,
+ .val_format_endian_default = REGMAP_ENDIAN_LITTLE,
+};
+
+struct regmap *syscon_regmap_init(struct device_node *np, void __iomem *base,
+ struct regmap_config *syscon_config)
+{
+ if (of_device_is_compatible(np, "sprd,atomic-syscon"))
+ return regmap_init(NULL, &sprd_syscon_regmap, base,
+ syscon_config);
+
+ return regmap_init_mmio(NULL, base, syscon_config);
+}
+
+MODULE_DESCRIPTION("Spreadtrum syscon support");
+MODULE_AUTHOR("Baolin Wang <baolin.wang@...soc.com>");
+MODULE_LICENSE("GPL v2");
--
2.17.1
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