On 30/04/18 12:18, Lee Jones wrote:

On Fri, 27 Apr 2018, matthias.bgg at kernel.org wrote:

quoted

From: Matthias Brugger <mbrugger@suse.com>

The MMSYS subsystem includes clocks and drm components.
This patch adds a MFD device to probe both drivers from the same
device tree compatible.

Signed-off-by: Matthias Brugger <mbrugger@suse.com>
---
 drivers/mfd/Kconfig     |  9 ++++++
 drivers/mfd/Makefile    |  2 ++
 drivers/mfd/mtk-mmsys.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 90 insertions(+)
 create mode 100644 drivers/mfd/mtk-mmsys.c

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index b860eb5aa194..d23a3b9a2c58 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig

@@ -378,6 +378,15 @@ config MFD_MC13XXX_I2C
 	help
 	  Select this if your MC13xxx is connected via an I2C bus.
 
+config MFD_MEDIATEK_MMSYS
+	tristate "Mediatek MMSYS interface"
+	select MFD_CORE
+	select REGMAP_MMIO
+	help
+	  Select this if you have a MMSYS subsystem in your SoC. The
+	  MMSYS subsystem has at least a clock driver part and some
+	  DRM components.
+
 config MFD_MXS_LRADC
 	tristate "Freescale i.MX23/i.MX28 LRADC"
 	depends on ARCH_MXS || COMPILE_TEST

diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index d9d2cf0d32ef..b96118bd68d9 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile

@@ -98,6 +98,8 @@ obj-$(CONFIG_MFD_MC13XXX)	+= mc13xxx-core.o
 obj-$(CONFIG_MFD_MC13XXX_SPI)	+= mc13xxx-spi.o
 obj-$(CONFIG_MFD_MC13XXX_I2C)	+= mc13xxx-i2c.o
 
+obj-$(CONFIG_MFD_MEDIATEK_MMSYS) += mtk-mmsys.o
+
 obj-$(CONFIG_MFD_CORE)		+= mfd-core.o
 
 obj-$(CONFIG_EZX_PCAP)		+= ezx-pcap.o

diff --git a/drivers/mfd/mtk-mmsys.c b/drivers/mfd/mtk-mmsys.c
new file mode 100644
index 000000000000..c802343fb1c6
--- /dev/null
+++ b/drivers/mfd/mtk-mmsys.c

@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+/*
+ * mtk-mmsys.c -- Mediatek MMSYS multi-function driver
+ *
+ * Copyright (c) 2018 Matthias Brugger <matthias.bgg@gmail.com>
+ *
+ * Author: Matthias Brugger <matthias.bgg@gmail.com>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/mfd/core.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+enum {
+	MMSYS_MT2701 = 1,
+};
+
+static const struct mfd_cell mmsys_mt2701_devs[] = {
+	{ .name = "clk-mt2701-mm", },
+	{ .name = "drm-mt2701-mm", },
+};
+
+static int mmsys_probe(struct platform_device *pdev)
+{
+	const struct mfd_cell *mmsys_cells;
+	int nr_cells;
+	long id;
+	int ret;
+
+	id = (long) of_device_get_match_data(&pdev->dev);
+	if (!id) {
+		dev_err(&pdev->dev, "of_device_get match_data() failed\n");
+		return -EINVAL;
+	}
+
+	switch (id) {
+	case MMSYS_MT2701:
+		mmsys_cells = mmsys_mt2701_devs;
+		nr_cells = ARRAY_SIZE(mmsys_mt2701_devs);
+		break;
+	default:
+		return -ENODEV;
+	}
+
+	ret = devm_mfd_add_devices(&pdev->dev, 0, mmsys_cells, nr_cells,
+					NULL, 0, NULL);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to add MFD devices %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+};

This driver is pretty pointless.  It doesn't actually do anything.

I think you just want to use "simple-mfd" instead.

I think the problem is, that right now we have two drivers which use the same
devicetree binding, which are clk and drm driver. With a simple-mfd we would
need two compatibles, and this would break backwards compatibility.

Regards,
Matthias