On Wed, 04 Jul 2018, Matthias Brugger wrote:

On 03/07/18 09:11, Lee Jones wrote:

quoted

On Mon, 25 Jun 2018, Matthias Brugger wrote:

quoted

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

quoted

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.

So what functionality does this driver provide you with that you do
not have currently?

I'm not sure if I get your question. Point is, that the MMSYS implementation for
mt8173 is broken, as it assumes that we can probe two drivers with the
mediatek,mt8173-mmsys compatible. Somehow it used to work, but from what I
understand it was a bug. So older devicetrees use just on mt8173-mmsys
compatible in ther DTB.

Okay, that is what I was getting at.  Thanks for the explanation.

Do you have a datasheet I can look at?

I would like to keep backwards compatibility for the device tree, that's why I
was searching for a solution where we can probe two drivers and came up with
this mfd solution.

So no new functionality, the clk driver provides the clock the drm components need.

-- 
Lee Jones [???]
Linaro Services Technical Lead
Linaro.org ? Open source software for ARM SoCs
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