[PATCH 2/3] hwspinlock: brcmstb hardware semaphore support

Kamal Dasu
2025-09-29T20:07:24Z

Added support for brmstb_hwspinlock driver that makes use of
the hwspinlock framework. Driver uses SUN_TOP_CTRL_SEMAPHORE_[1:15]
registers to implement the hardware semaphore. With this change
other brcmstb drivers can use hwspin_trylock() and hwspin_unlock()
apis and make use of this hwspinlock framework. Other driver dt nodes
just need to use a reference to the &hwspinlock and the lock id
they want to use.
e.g. hwlocks = <&hwspinlock0 0>;

Signed-off-by: Kamal Dasu <kamal.dasu@broadcom.com>
---
drivers/hwspinlock/Kconfig | 9 +++
drivers/hwspinlock/Makefile | 1 +
drivers/hwspinlock/brcmstb_hwspinlock.c | 98 +++++++++++++++++++++++++
3 files changed, 108 insertions(+)
create mode 100644 drivers/hwspinlock/brcmstb_hwspinlock.c

diff --git a/drivers/hwspinlock/Kconfig b/drivers/hwspinlock/Kconfig
index 3874d15b0e9b..551afa8df2d0 100644
--- a/drivers/hwspinlock/Kconfig
+++ b/drivers/hwspinlock/Kconfig
@@ -63,4 +63,13 @@ config HSEM_U8500

If unsure, say N.

+config HWSPINLOCK_BRCMSTB
+ tristate "Broadcom Setttop Hardware Semaphore functionality"
+ depends on ARCH_BRCMSTB || COMPILE_TEST
+ help
+ Broadcom settop hwspinlock driver.
+ Say y here to support the Broadcom Hardware Semaphore functionality, which
+ provides a synchronisation mechanism on the SoC.
+
+ If unsure, say N.
endif # HWSPINLOCK
diff --git a/drivers/hwspinlock/Makefile b/drivers/hwspinlock/Makefile
index a0f16c9aaa82..4f5c05403209 100644
--- a/drivers/hwspinlock/Makefile
+++ b/drivers/hwspinlock/Makefile
@@ -10,3 +10,4 @@ obj-$(CONFIG_HWSPINLOCK_SPRD) += sprd_hwspinlock.o
obj-$(CONFIG_HWSPINLOCK_STM32) += stm32_hwspinlock.o
obj-$(CONFIG_HWSPINLOCK_SUN6I) += sun6i_hwspinlock.o
obj-$(CONFIG_HSEM_U8500) += u8500_hsem.o
+obj-$(CONFIG_HWSPINLOCK_BRCMSTB) += brcmstb_hwspinlock.o
diff --git a/drivers/hwspinlock/brcmstb_hwspinlock.c b/drivers/hwspinlock/brcmstb_hwspinlock.c
new file mode 100644
index 000000000000..56206431a94c
--- /dev/null
+++ b/drivers/hwspinlock/brcmstb_hwspinlock.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * brcmstb HWSEM driver
+ *
+ * Copyright (C) 2025 Broadcom
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/hwspinlock.h>
+#include <linux/platform_device.h>
+#include <linux/mod_devicetable.h>
+#include "hwspinlock_internal.h"
+
+#define BRCMSTB_MAX_SEMAPHORES 16
+#define RESET_SEMAPHORE 0
+
+#define HWSPINLOCK_VAL 'L'
+
+static int brcmstb_hwspinlock_trylock(struct hwspinlock *lock)
+{
+ void __iomem *lock_addr = (void __iomem *)lock->priv;
+
+ writel(HWSPINLOCK_VAL, lock_addr);
+
+ return (readl(lock_addr) == HWSPINLOCK_VAL);
+}
+
+static void brcmstb_hwspinlock_unlock(struct hwspinlock *lock)
+{
+ void __iomem *lock_addr = (void __iomem *)lock->priv;
+
+ /* release the lock by writing 0 to it */
+ writel(RESET_SEMAPHORE, lock_addr);
+}
+
+static void brcmstb_hwspinlock_relax(struct hwspinlock *lock)
+{
+ ndelay(50);
+}
+
+static const struct hwspinlock_ops brcmstb_hwspinlock_ops = {
+ .trylock = brcmstb_hwspinlock_trylock,
+ .unlock = brcmstb_hwspinlock_unlock,
+ .relax = brcmstb_hwspinlock_relax,
+};
+
+static int brcmstb_hwspinlock_probe(struct platform_device *pdev)
+{
+ struct hwspinlock_device *bank;
+ struct hwspinlock *hwlock;
+ void __iomem *io_base;
+ int i, num_locks = BRCMSTB_MAX_SEMAPHORES;
+
+ io_base = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(io_base)) {
+ dev_err(&pdev->dev, "semaphore iobase mapping error\n");
+ return PTR_ERR(io_base);
+ }
+
+ bank = devm_kzalloc(&pdev->dev, struct_size(bank, lock, num_locks),
+ GFP_KERNEL);
+ if (!bank)
+ return -ENOMEM;
+
+ platform_set_drvdata(pdev, bank);
+
+ for (i = 0, hwlock = &bank->lock[0]; i < num_locks; i++, hwlock++)
+ hwlock->priv = (void __iomem *)(io_base + sizeof(u32) * i);
+
+ return devm_hwspin_lock_register(&pdev->dev, bank,
+ &brcmstb_hwspinlock_ops,
+ 0, num_locks);
+}
+
+static const struct of_device_id brcmstb_hwspinlock_ids[] = {
+ { .compatible = "brcm,brcmstb-hwspinlock", },
+ { /* end */ },
+};
+MODULE_DEVICE_TABLE(of, brcmstb_hwspinlock_ids);
+
+static struct platform_driver brcmstb_hwspinlock_driver = {
+ .probe = brcmstb_hwspinlock_probe,
+ .driver = {
+ .name = "brcmstb_hwspinlock",
+ .of_match_table = brcmstb_hwspinlock_ids,
+ },
+};
+
+module_platform_driver(brcmstb_hwspinlock_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Hardware Spinlock driver for brcmstb");
+MODULE_AUTHOR("Kamal Dasu <kdasu.dasu@broadcom.com>");
--
2.34.1