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Message-ID: <b6301691-a9f6-64fe-dd8a-ffe51fad6799@suse.com>
Date: Wed, 4 Jul 2018 18:17:35 +0200
From: Matthias Brugger <mbrugger@...e.com>
To: Lee Jones <lee.jones@...aro.org>,
Matthias Brugger <matthias.bgg@...il.com>
Cc: matthias.bgg@...nel.org, ulrich.hecht+renesas@...il.com,
laurent.pinchart@...asonboard.com, ck.hu@...iatek.com,
p.zabel@...gutronix.de, airlied@...ux.ie, robh+dt@...nel.org,
mark.rutland@....com, mturquette@...libre.com,
sboyd@...eaurora.org, davem@...emloft.net,
gregkh@...uxfoundation.org, mchehab@...nel.org,
rdunlap@...radead.org, sean.wang@...iatek.com,
linux-clk@...r.kernel.org, linux@...linux.org.uk,
dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
linux-mediatek@...ts.infradead.org
Subject: Re: [v3 03/10] mfd: mtk-mmsys: Add mmsys driver
On 03/07/18 09:11, Lee Jones wrote:
> On Mon, 25 Jun 2018, Matthias Brugger wrote:
>> On 30/04/18 12:18, Lee Jones wrote:
>>> On Fri, 27 Apr 2018, matthias.bgg@...nel.org wrote:
>>>
>>>> From: Matthias Brugger <mbrugger@...e.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@...e.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@...il.com>
>>>> + *
>>>> + * Author: Matthias Brugger <matthias.bgg@...il.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.
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.
Regards,
Matthias
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