RE: [PATCH 2/2] drivers: misc: add ripple counter driver

-----Original Message-----
From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Sent: Friday, February 26, 2021 9:14 AM
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>; Rob Herring
[off-list ref]
Cc: devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; Arnd Bergmann
[off-list ref]; linux-clk@vger.kernel.org; Rasmus Villemoes
[off-list ref]
Subject: [PATCH 2/2] drivers: misc: add ripple counter driver

The only purpose of this driver is to serve as a consumer of the input
clock, to prevent it from being disabled by clk_disable_unused().

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 drivers/misc/Kconfig      |  7 +++++++
 drivers/misc/Makefile     |  1 +
 drivers/misc/ripple-ctr.c | 31 +++++++++++++++++++++++++++++++
 3 files changed, 39 insertions(+)
 create mode 100644 drivers/misc/ripple-ctr.c

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index f532c59bb59b..44b0b6ce42df 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig

@@ -445,6 +445,13 @@ config HISI_HIKEY_USB
 	  switching between the dual-role USB-C port and the USB-A host ports
 	  using only one USB controller.

+config RIPPLE_CTR
+	tristate "Trivial ripple counter driver"
+	help
+	  This provides a stub driver for a ripple counter, whose
+	  only purpose is to request and enable the clock source
+	  driving the counter.
+
 source "drivers/misc/c2port/Kconfig"
 source "drivers/misc/eeprom/Kconfig"
 source "drivers/misc/cb710/Kconfig"

diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 99b6f15a3c70..d560163068a9 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile

@@ -56,3 +56,4 @@ obj-$(CONFIG_HABANA_AI)		+= habanalabs/
 obj-$(CONFIG_UACCE)		+= uacce/
 obj-$(CONFIG_XILINX_SDFEC)	+= xilinx_sdfec.o
 obj-$(CONFIG_HISI_HIKEY_USB)	+= hisi_hikey_usb.o
+obj-$(CONFIG_RIPPLE_CTR)	+= ripple-ctr.o

diff --git a/drivers/misc/ripple-ctr.c b/drivers/misc/ripple-ctr.c
new file mode 100644
index 000000000000..f086eaf335df
--- /dev/null
+++ b/drivers/misc/ripple-ctr.c

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+static int ripple_ctr_probe(struct platform_device *pdev)
+{
+	struct clk *clk;
+
+	clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+	return clk_prepare_enable(clk);
+}
+
+static const struct of_device_id ripple_ctr_ids[] = {
+	{ .compatible = "linux,ripple-counter", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ripple_ctr_ids);
+
+static struct platform_driver ripple_ctr_driver = {
+	.driver	= {
+		.name		= "ripple-counter",
+		.of_match_table	= ripple_ctr_ids,
+	},
+	.probe	= ripple_ctr_probe,
+};
+module_platform_driver(ripple_ctr_driver);