linux-kernel - Re: [PATCH 2/3] hwspinlock: brcmstb hardware semaphore support

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Message-ID: <20251001025305.GA23170@nxa18884-linux.ap.freescale.net>
Date: Wed, 1 Oct 2025 10:53:05 +0800
From: Peng Fan <peng.fan@....nxp.com>
To: Kamal Dasu <kamal.dasu@...adcom.com>
Cc: bcm-kernel-feedback-list@...adcom.com, andersson@...nel.org,
	baolin.wang@...ux.alibaba.com, robh@...nel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org, florian.fainelli@...adcom.com,
	linux-remoteproc@...r.kernel.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] hwspinlock: brcmstb hardware semaphore support

On Mon, Sep 29, 2025 at 04:06:26PM -0400, Kamal Dasu wrote:
>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@...adcom.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

Should be put above "config HWSPINLOCK_OMAP" to follow the order.

>+	tristate "Broadcom Setttop Hardware Semaphore functionality"
...
>--- 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

Put above "obj-$(CONFIG_HWSPINLOCK_OMAP)           += omap_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>

Sort the included headers.

>+#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);

I not see users of drvdata in this driver, is this needed or I miss something?

>+
>+	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);

Seems all "brcm,brcmstb-hwspinlock" compatible devices have 16 sema locks.
If this is true, it is ok. Otherwise better not fix num_locks to
BRCMSTB_MAX_SEMAPHORES. "MAX" implys that not all devices have 16 sema locks.

Thanks,
Peng