[PATCH v7] mfd: syscon: Decouple syscon interface from platform devices

[PATCH v7] mfd: syscon: Decouple syscon interface from platform devices

[Pankaj Dubey]

Currently a syscon entity can be only registered directly through a
platform device that binds to a dedicated syscon driver. However in
certain use cases it is desirable to make a device used with another
driver a syscon interface provider.

For example, certain SoCs (e.g. Exynos) contain system controller
blocks which perform various functions such as power domain control,
CPU power management, low power mode control, but in addition contain
certain IP integration glue, such as various signal masks,
coprocessor power control, etc. In such case, there is a need to have
a dedicated driver for such system controller but also share registers
with other drivers. The latter is where the syscon interface is helpful.

In case of DT based platforms, this patch decouples syscon object from
syscon platform driver, and allows to create syscon objects first time
when it is required by calling of syscon_regmap_lookup_by APIs and keep
a list of such syscon objects along with syscon provider device_nodes
and regmap handles.

For non-DT based platforms, this patch keeps syscon platform driver
structure so that syscon can be probed and such non-DT based drivers
can use syscon_regmap_lookup_by_pdev API and access regmap handles.
Once all users of "syscon_regmap_lookup_by_pdev" migrated to DT based,
we can completely remove platform driver of syscon, and keep only helper
functions to get regmap handles.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Suggested-by: Tomasz Figa <tomasz.figa@gmail.com>
Tested-by: Vivek Gautam <gautam.vivek@samsung.com>
Tested-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
---
Patch v6 and related discussions can be found here [1].

Change since v5:
 - Addressed review comments from "Heiko Stuebner".
 - Updated commit description.
 - Including Arnd's and Heiko's Reviewed-by.

Change since v5:
 - Dropping creation of dummy platform device in of_syscon_register.
 - As we are changing syscon to decouple from platform_device, creation of 
   dummy platform_device does not look good option, and as suggested by Arnd,
   I made another attempt so that regmap_mmio_init API should work with NULL
   dev pointer itself. Since regmap needs to know about Syscon device node
   properties so let's parse device node of syscon in syscon itself for any
   such properties and using regmap_config parameter pass all such information
   to regmap. Other concern of crashes due to NULL dev pointer in regmap already
   addressed in separate patches of regmap. Please see [2] and [3].

Changes since v4:
 - Addressed Tomasz Figa's comments for v4.
 - Added error handing in of_syscon_register function.
 - Using devm_regmap_init_mmio instead of regmap_init_mmio.

Changes since v3:
 - Addressed Arnd's comment for v2.
 - Updated of_syscon_register for adding dev pointer in regmap_init_mmio.
 - For early users created dummy platform device.

Changes since v2:
 - Added back platform device support from syscon, with one change that
   syscon will not be probed for DT based platform.
 - Added back syscon_regmap_lookup_by_pdevname API so that non-DT base
   users of syscon will not be broken.
 - Removed unwanted change in syscon.h.
 - Modified Signed-off-by list, added Suggested-by of Tomasz Figa and
   Arnd Bergmann.
 - Added Tested-by of Vivek Gautam for testing on Exynos platform.

Changes since v1:
 - Removed of_syscon_unregister function.
 - Modified of_syscon_register function and it will be used by syscon.c
   to create syscon objects whenever required.
 - Removed platform device support from syscon.
 - Removed syscon_regmap_lookup_by_pdevname API support.
 - As there are significant changes w.r.t patchset v1, I am taking over
   author for this patchset from Tomasz Figa.

[1]: https://lkml.org/lkml/2014/9/29/99
[2]: https://lkml.org/lkml/2014/9/18/130
[3]: https://lkml.org/lkml/2014/9/27/2
 drivers/mfd/syscon.c |   96 ++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 74 insertions(+), 22 deletions(-)

diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
index ca15878..72373b1 100644
--- a/drivers/mfd/syscon.c
+++ b/drivers/mfd/syscon.c
@@ -15,6 +15,7 @@
 #include <linux/err.h>
 #include <linux/io.h>
 #include <linux/module.h>
+#include <linux/list.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/of_platform.h>
@@ -22,31 +23,94 @@
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
 #include <linux/mfd/syscon.h>
+#include <linux/slab.h>
 
 static struct platform_driver syscon_driver;
 
+static DEFINE_SPINLOCK(syscon_list_slock);
+static LIST_HEAD(syscon_list);
+
 struct syscon {
+	struct device_node *np;
 	struct regmap *regmap;
+	struct list_head list;
+};
+
+static struct regmap_config syscon_regmap_config = {
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = 4,
 };
 
-static int syscon_match_node(struct device *dev, void *data)
+static struct syscon *of_syscon_register(struct device_node *np)
 {
-	struct device_node *dn = data;
+	struct syscon *syscon;
+	struct regmap *regmap;
+	void __iomem *base;
+	int ret;
+	struct regmap_config syscon_config = syscon_regmap_config;
+
+	if (!of_device_is_compatible(np, "syscon"))
+		return ERR_PTR(-EINVAL);
+
+	syscon = kzalloc(sizeof(*syscon), GFP_KERNEL);
+	if (!syscon)
+		return ERR_PTR(-ENOMEM);
+
+	base = of_iomap(np, 0);
+	if (!base) {
+		ret = -ENOMEM;
+		goto err_map;
+	}
+
+	/* Parse the device's DT node for an endianness specification */
+	if (of_property_read_bool(np, "big-endian"))
+		syscon_config.val_format_endian = REGMAP_ENDIAN_BIG;
+	 else if (of_property_read_bool(np, "little-endian"))
+		syscon_config.val_format_endian = REGMAP_ENDIAN_LITTLE;
+
+	regmap = regmap_init_mmio(NULL, base, &syscon_config);
+	if (IS_ERR(regmap)) {
+		pr_err("regmap init failed\n");
+		ret = PTR_ERR(regmap);
+		goto err_regmap;
+	}
+
+	syscon->regmap = regmap;
+	syscon->np = np;
+
+	spin_lock(&syscon_list_slock);
+	list_add_tail(&syscon->list, &syscon_list);
+	spin_unlock(&syscon_list_slock);
 
-	return (dev->of_node == dn) ? 1 : 0;
+	return syscon;
+
+err_regmap:
+	iounmap(base);
+err_map:
+	kfree(syscon);
+	return ERR_PTR(ret);
 }
 
 struct regmap *syscon_node_to_regmap(struct device_node *np)
 {
-	struct syscon *syscon;
-	struct device *dev;
+	struct syscon *entry, *syscon = NULL;
 
-	dev = driver_find_device(&syscon_driver.driver, NULL, np,
-				 syscon_match_node);
-	if (!dev)
-		return ERR_PTR(-EPROBE_DEFER);
+	spin_lock(&syscon_list_slock);
 
-	syscon = dev_get_drvdata(dev);
+	list_for_each_entry(entry, &syscon_list, list)
+		if (entry->np == np) {
+			syscon = entry;
+			break;
+		}
+
+	spin_unlock(&syscon_list_slock);
+
+	if (!syscon)
+		syscon = of_syscon_register(np);
+
+	if (IS_ERR(syscon))
+		return ERR_CAST(syscon);
 
 	return syscon->regmap;
 }
@@ -110,17 +174,6 @@ struct regmap *syscon_regmap_lookup_by_phandle(struct device_node *np,
 }
 EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_phandle);
 
-static const struct of_device_id of_syscon_match[] = {
-	{ .compatible = "syscon", },
-	{ },
-};
-
-static struct regmap_config syscon_regmap_config = {
-	.reg_bits = 32,
-	.val_bits = 32,
-	.reg_stride = 4,
-};
-
 static int syscon_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -167,7 +220,6 @@ static struct platform_driver syscon_driver = {
 	.driver = {
 		.name = "syscon",
 		.owner = THIS_MODULE,
-		.of_match_table = of_syscon_match,
 	},
 	.probe		= syscon_probe,
 	.id_table	= syscon_ids,
-- 
1.7.9.5

Re: [PATCH v7] mfd: syscon: Decouple syscon interface from platform devices

[Doug Anderson]

Pankaj,

On Tue, Sep 30, 2014 at 1:35 AM, Pankaj Dubey <pankaj.dubey@samsung.com> wrote:
> Currently a syscon entity can be only registered directly through a
> platform device that binds to a dedicated syscon driver. However in
> certain use cases it is desirable to make a device used with another
> driver a syscon interface provider.
>
> For example, certain SoCs (e.g. Exynos) contain system controller
> blocks which perform various functions such as power domain control,
> CPU power management, low power mode control, but in addition contain
> certain IP integration glue, such as various signal masks,
> coprocessor power control, etc. In such case, there is a need to have
> a dedicated driver for such system controller but also share registers
> with other drivers. The latter is where the syscon interface is helpful.
>
> In case of DT based platforms, this patch decouples syscon object from
> syscon platform driver, and allows to create syscon objects first time
> when it is required by calling of syscon_regmap_lookup_by APIs and keep
> a list of such syscon objects along with syscon provider device_nodes
> and regmap handles.
>
> For non-DT based platforms, this patch keeps syscon platform driver
> structure so that syscon can be probed and such non-DT based drivers
> can use syscon_regmap_lookup_by_pdev API and access regmap handles.
> Once all users of "syscon_regmap_lookup_by_pdev" migrated to DT based,
> we can completely remove platform driver of syscon, and keep only helper
> functions to get regmap handles.
>
> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Suggested-by: Tomasz Figa <tomasz.figa@gmail.com>
> Tested-by: Vivek Gautam <gautam.vivek@samsung.com>
> Tested-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
> Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> Tested-by: Heiko Stuebner <heiko@sntech.de>
> Reviewed-by: Heiko Stuebner <heiko@sntech.de>
> ---
> Patch v6 and related discussions can be found here [1].
>
> Change since v5:
>  - Addressed review comments from "Heiko Stuebner".
>  - Updated commit description.
>  - Including Arnd's and Heiko's Reviewed-by.
>
> Change since v5:
>  - Dropping creation of dummy platform device in of_syscon_register.
>  - As we are changing syscon to decouple from platform_device, creation of
>    dummy platform_device does not look good option, and as suggested by Arnd,
>    I made another attempt so that regmap_mmio_init API should work with NULL
>    dev pointer itself. Since regmap needs to know about Syscon device node
>    properties so let's parse device node of syscon in syscon itself for any
>    such properties and using regmap_config parameter pass all such information
>    to regmap. Other concern of crashes due to NULL dev pointer in regmap already
>    addressed in separate patches of regmap. Please see [2] and [3].
>
> Changes since v4:
>  - Addressed Tomasz Figa's comments for v4.
>  - Added error handing in of_syscon_register function.
>  - Using devm_regmap_init_mmio instead of regmap_init_mmio.
>
> Changes since v3:
>  - Addressed Arnd's comment for v2.
>  - Updated of_syscon_register for adding dev pointer in regmap_init_mmio.
>  - For early users created dummy platform device.
>
> Changes since v2:
>  - Added back platform device support from syscon, with one change that
>    syscon will not be probed for DT based platform.
>  - Added back syscon_regmap_lookup_by_pdevname API so that non-DT base
>    users of syscon will not be broken.
>  - Removed unwanted change in syscon.h.
>  - Modified Signed-off-by list, added Suggested-by of Tomasz Figa and
>    Arnd Bergmann.
>  - Added Tested-by of Vivek Gautam for testing on Exynos platform.
>
> Changes since v1:
>  - Removed of_syscon_unregister function.
>  - Modified of_syscon_register function and it will be used by syscon.c
>    to create syscon objects whenever required.
>  - Removed platform device support from syscon.
>  - Removed syscon_regmap_lookup_by_pdevname API support.
>  - As there are significant changes w.r.t patchset v1, I am taking over
>    author for this patchset from Tomasz Figa.
>
> [1]: https://lkml.org/lkml/2014/9/29/99
> [2]: https://lkml.org/lkml/2014/9/18/130
> [3]: https://lkml.org/lkml/2014/9/27/2
>  drivers/mfd/syscon.c |   96 ++++++++++++++++++++++++++++++++++++++------------
>  1 file changed, 74 insertions(+), 22 deletions(-)

You probably already have enough tags, but just in case.  ;)  On an
rk3288-based system (this patch backported to 3.14):

Tested-by: Doug Anderson <dianders@chromium.org>

RE: [PATCH v7] mfd: syscon: Decouple syscon interface from platform devices

[Pankaj Dubey]

Hi Lee,

On Tuesday, September 30, 2014 9:39 PM Doug Anderson wrote,
> Subject: Re: [PATCH v7] mfd: syscon: Decouple syscon interface from platform
> devices
> 
> Pankaj,
> 
> On Tue, Sep 30, 2014 at 1:35 AM, Pankaj Dubey <pankaj.dubey@samsung.com>
> wrote:
> > Currently a syscon entity can be only registered directly through a
> > platform device that binds to a dedicated syscon driver. However in
> > certain use cases it is desirable to make a device used with another
> > driver a syscon interface provider.
> >
> > For example, certain SoCs (e.g. Exynos) contain system controller
> > blocks which perform various functions such as power domain control,
> > CPU power management, low power mode control, but in addition contain
> > certain IP integration glue, such as various signal masks, coprocessor
> > power control, etc. In such case, there is a need to have a dedicated
> > driver for such system controller but also share registers with other
> > drivers. The latter is where the syscon interface is helpful.
> >
> > In case of DT based platforms, this patch decouples syscon object from
> > syscon platform driver, and allows to create syscon objects first time
> > when it is required by calling of syscon_regmap_lookup_by APIs and
> > keep a list of such syscon objects along with syscon provider
> > device_nodes and regmap handles.
> >
> > For non-DT based platforms, this patch keeps syscon platform driver
> > structure so that syscon can be probed and such non-DT based drivers
> > can use syscon_regmap_lookup_by_pdev API and access regmap handles.
> > Once all users of "syscon_regmap_lookup_by_pdev" migrated to DT based,
> > we can completely remove platform driver of syscon, and keep only
> > helper functions to get regmap handles.
> >
> > Suggested-by: Arnd Bergmann <arnd@arndb.de>
> > Suggested-by: Tomasz Figa <tomasz.figa@gmail.com>
> > Tested-by: Vivek Gautam <gautam.vivek@samsung.com>
> > Tested-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
> > Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> > Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> > Tested-by: Heiko Stuebner <heiko@sntech.de>
> > Reviewed-by: Heiko Stuebner <heiko@sntech.de>
> > ---
> > Patch v6 and related discussions can be found here [1].
> >
> > Change since v5:
> >  - Addressed review comments from "Heiko Stuebner".
> >  - Updated commit description.
> >  - Including Arnd's and Heiko's Reviewed-by.
> >
> > Change since v5:
> >  - Dropping creation of dummy platform device in of_syscon_register.
> >  - As we are changing syscon to decouple from platform_device, creation of
> >    dummy platform_device does not look good option, and as suggested by Arnd,
> >    I made another attempt so that regmap_mmio_init API should work with NULL
> >    dev pointer itself. Since regmap needs to know about Syscon device node
> >    properties so let's parse device node of syscon in syscon itself for any
> >    such properties and using regmap_config parameter pass all such information
> >    to regmap. Other concern of crashes due to NULL dev pointer in regmap already
> >    addressed in separate patches of regmap. Please see [2] and [3].
> >
> > Changes since v4:
> >  - Addressed Tomasz Figa's comments for v4.
> >  - Added error handing in of_syscon_register function.
> >  - Using devm_regmap_init_mmio instead of regmap_init_mmio.
> >
> > Changes since v3:
> >  - Addressed Arnd's comment for v2.
> >  - Updated of_syscon_register for adding dev pointer in regmap_init_mmio.
> >  - For early users created dummy platform device.
> >
> > Changes since v2:
> >  - Added back platform device support from syscon, with one change that
> >    syscon will not be probed for DT based platform.
> >  - Added back syscon_regmap_lookup_by_pdevname API so that non-DT base
> >    users of syscon will not be broken.
> >  - Removed unwanted change in syscon.h.
> >  - Modified Signed-off-by list, added Suggested-by of Tomasz Figa and
> >    Arnd Bergmann.
> >  - Added Tested-by of Vivek Gautam for testing on Exynos platform.
> >
> > Changes since v1:
> >  - Removed of_syscon_unregister function.
> >  - Modified of_syscon_register function and it will be used by syscon.c
> >    to create syscon objects whenever required.
> >  - Removed platform device support from syscon.
> >  - Removed syscon_regmap_lookup_by_pdevname API support.
> >  - As there are significant changes w.r.t patchset v1, I am taking over
> >    author for this patchset from Tomasz Figa.
> >
> > [1]: https://lkml.org/lkml/2014/9/29/99
> > [2]: https://lkml.org/lkml/2014/9/18/130
> > [3]: https://lkml.org/lkml/2014/9/27/2
> >  drivers/mfd/syscon.c |   96
> ++++++++++++++++++++++++++++++++++++++------------
> >  1 file changed, 74 insertions(+), 22 deletions(-)
> 
> You probably already have enough tags, but just in case.  ;)  On an rk3288-based
> system (this patch backported to 3.14):
> 
> Tested-by: Doug Anderson <dianders@chromium.org>

I think now we can take have this patch in. So will you please take this patch.

Thanks,
Pankaj Dubey

Re: [PATCH v7] mfd: syscon: Decouple syscon interface from platform devices

[Lee Jones]

On Mon, 06 Oct 2014, Pankaj Dubey wrote:

> Hi Lee,
> 
> On Tuesday, September 30, 2014 9:39 PM Doug Anderson wrote,
> > Subject: Re: [PATCH v7] mfd: syscon: Decouple syscon interface from platform
> > devices
> > 
> > Pankaj,
> > 
> > On Tue, Sep 30, 2014 at 1:35 AM, Pankaj Dubey <pankaj.dubey@samsung.com>
> > wrote:
> > > Currently a syscon entity can be only registered directly through a
> > > platform device that binds to a dedicated syscon driver. However in
> > > certain use cases it is desirable to make a device used with another
> > > driver a syscon interface provider.
> > >
> > > For example, certain SoCs (e.g. Exynos) contain system controller
> > > blocks which perform various functions such as power domain control,
> > > CPU power management, low power mode control, but in addition contain
> > > certain IP integration glue, such as various signal masks, coprocessor
> > > power control, etc. In such case, there is a need to have a dedicated
> > > driver for such system controller but also share registers with other
> > > drivers. The latter is where the syscon interface is helpful.
> > >
> > > In case of DT based platforms, this patch decouples syscon object from
> > > syscon platform driver, and allows to create syscon objects first time
> > > when it is required by calling of syscon_regmap_lookup_by APIs and
> > > keep a list of such syscon objects along with syscon provider
> > > device_nodes and regmap handles.
> > >
> > > For non-DT based platforms, this patch keeps syscon platform driver
> > > structure so that syscon can be probed and such non-DT based drivers
> > > can use syscon_regmap_lookup_by_pdev API and access regmap handles.
> > > Once all users of "syscon_regmap_lookup_by_pdev" migrated to DT based,
> > > we can completely remove platform driver of syscon, and keep only
> > > helper functions to get regmap handles.
> > >
> > > Suggested-by: Arnd Bergmann <arnd@arndb.de>
> > > Suggested-by: Tomasz Figa <tomasz.figa@gmail.com>
> > > Tested-by: Vivek Gautam <gautam.vivek@samsung.com>
> > > Tested-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
> > > Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> > > Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> > > Tested-by: Heiko Stuebner <heiko@sntech.de>
> > > Reviewed-by: Heiko Stuebner <heiko@sntech.de>
> > > ---
> > > Patch v6 and related discussions can be found here [1].
> > >
> > > Change since v5:
> > >  - Addressed review comments from "Heiko Stuebner".
> > >  - Updated commit description.
> > >  - Including Arnd's and Heiko's Reviewed-by.
> > >
> > > Change since v5:
> > >  - Dropping creation of dummy platform device in of_syscon_register.
> > >  - As we are changing syscon to decouple from platform_device, creation of
> > >    dummy platform_device does not look good option, and as suggested by Arnd,
> > >    I made another attempt so that regmap_mmio_init API should work with NULL
> > >    dev pointer itself. Since regmap needs to know about Syscon device node
> > >    properties so let's parse device node of syscon in syscon itself for any
> > >    such properties and using regmap_config parameter pass all such information
> > >    to regmap. Other concern of crashes due to NULL dev pointer in regmap already
> > >    addressed in separate patches of regmap. Please see [2] and [3].
> > >
> > > Changes since v4:
> > >  - Addressed Tomasz Figa's comments for v4.
> > >  - Added error handing in of_syscon_register function.
> > >  - Using devm_regmap_init_mmio instead of regmap_init_mmio.
> > >
> > > Changes since v3:
> > >  - Addressed Arnd's comment for v2.
> > >  - Updated of_syscon_register for adding dev pointer in regmap_init_mmio.
> > >  - For early users created dummy platform device.
> > >
> > > Changes since v2:
> > >  - Added back platform device support from syscon, with one change that
> > >    syscon will not be probed for DT based platform.
> > >  - Added back syscon_regmap_lookup_by_pdevname API so that non-DT base
> > >    users of syscon will not be broken.
> > >  - Removed unwanted change in syscon.h.
> > >  - Modified Signed-off-by list, added Suggested-by of Tomasz Figa and
> > >    Arnd Bergmann.
> > >  - Added Tested-by of Vivek Gautam for testing on Exynos platform.
> > >
> > > Changes since v1:
> > >  - Removed of_syscon_unregister function.
> > >  - Modified of_syscon_register function and it will be used by syscon.c
> > >    to create syscon objects whenever required.
> > >  - Removed platform device support from syscon.
> > >  - Removed syscon_regmap_lookup_by_pdevname API support.
> > >  - As there are significant changes w.r.t patchset v1, I am taking over
> > >    author for this patchset from Tomasz Figa.
> > >
> > > [1]: https://lkml.org/lkml/2014/9/29/99
> > > [2]: https://lkml.org/lkml/2014/9/18/130
> > > [3]: https://lkml.org/lkml/2014/9/27/2
> > >  drivers/mfd/syscon.c |   96
> > ++++++++++++++++++++++++++++++++++++++------------
> > >  1 file changed, 74 insertions(+), 22 deletions(-)
> > 
> > You probably already have enough tags, but just in case.  ;)  On an rk3288-based
> > system (this patch backported to 3.14):
> > 
> > Tested-by: Doug Anderson <dianders@chromium.org>
> 
> I think now we can take have this patch in. So will you please take this patch.

I plan to take this when the merge window has closed.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

Re: [PATCH v7] mfd: syscon: Decouple syscon interface from platform devices

[Lee Jones]

On Tue, 30 Sep 2014, Pankaj Dubey wrote:

> Currently a syscon entity can be only registered directly through a
> platform device that binds to a dedicated syscon driver. However in
> certain use cases it is desirable to make a device used with another
> driver a syscon interface provider.
> 
> For example, certain SoCs (e.g. Exynos) contain system controller
> blocks which perform various functions such as power domain control,
> CPU power management, low power mode control, but in addition contain
> certain IP integration glue, such as various signal masks,
> coprocessor power control, etc. In such case, there is a need to have
> a dedicated driver for such system controller but also share registers
> with other drivers. The latter is where the syscon interface is helpful.
> 
> In case of DT based platforms, this patch decouples syscon object from
> syscon platform driver, and allows to create syscon objects first time
> when it is required by calling of syscon_regmap_lookup_by APIs and keep
> a list of such syscon objects along with syscon provider device_nodes
> and regmap handles.
> 
> For non-DT based platforms, this patch keeps syscon platform driver
> structure so that syscon can be probed and such non-DT based drivers
> can use syscon_regmap_lookup_by_pdev API and access regmap handles.
> Once all users of "syscon_regmap_lookup_by_pdev" migrated to DT based,
> we can completely remove platform driver of syscon, and keep only helper
> functions to get regmap handles.
> 
> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Suggested-by: Tomasz Figa <tomasz.figa@gmail.com>
> Tested-by: Vivek Gautam <gautam.vivek@samsung.com>
> Tested-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
> Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> Tested-by: Heiko Stuebner <heiko@sntech.de>
> Reviewed-by: Heiko Stuebner <heiko@sntech.de>

Applied for v3.19.

> ---
> Patch v6 and related discussions can be found here [1].
> 
> Change since v5:
>  - Addressed review comments from "Heiko Stuebner".
>  - Updated commit description.
>  - Including Arnd's and Heiko's Reviewed-by.
> 
> Change since v5:
>  - Dropping creation of dummy platform device in of_syscon_register.
>  - As we are changing syscon to decouple from platform_device, creation of 
>    dummy platform_device does not look good option, and as suggested by Arnd,
>    I made another attempt so that regmap_mmio_init API should work with NULL
>    dev pointer itself. Since regmap needs to know about Syscon device node
>    properties so let's parse device node of syscon in syscon itself for any
>    such properties and using regmap_config parameter pass all such information
>    to regmap. Other concern of crashes due to NULL dev pointer in regmap already
>    addressed in separate patches of regmap. Please see [2] and [3].
> 
> Changes since v4:
>  - Addressed Tomasz Figa's comments for v4.
>  - Added error handing in of_syscon_register function.
>  - Using devm_regmap_init_mmio instead of regmap_init_mmio.
> 
> Changes since v3:
>  - Addressed Arnd's comment for v2.
>  - Updated of_syscon_register for adding dev pointer in regmap_init_mmio.
>  - For early users created dummy platform device.
> 
> Changes since v2:
>  - Added back platform device support from syscon, with one change that
>    syscon will not be probed for DT based platform.
>  - Added back syscon_regmap_lookup_by_pdevname API so that non-DT base
>    users of syscon will not be broken.
>  - Removed unwanted change in syscon.h.
>  - Modified Signed-off-by list, added Suggested-by of Tomasz Figa and
>    Arnd Bergmann.
>  - Added Tested-by of Vivek Gautam for testing on Exynos platform.
> 
> Changes since v1:
>  - Removed of_syscon_unregister function.
>  - Modified of_syscon_register function and it will be used by syscon.c
>    to create syscon objects whenever required.
>  - Removed platform device support from syscon.
>  - Removed syscon_regmap_lookup_by_pdevname API support.
>  - As there are significant changes w.r.t patchset v1, I am taking over
>    author for this patchset from Tomasz Figa.
> 
> [1]: https://lkml.org/lkml/2014/9/29/99
> [2]: https://lkml.org/lkml/2014/9/18/130
> [3]: https://lkml.org/lkml/2014/9/27/2
>  drivers/mfd/syscon.c |   96 ++++++++++++++++++++++++++++++++++++++------------
>  1 file changed, 74 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
> index ca15878..72373b1 100644
> --- a/drivers/mfd/syscon.c
> +++ b/drivers/mfd/syscon.c
> @@ -15,6 +15,7 @@
>  #include <linux/err.h>
>  #include <linux/io.h>
>  #include <linux/module.h>
> +#include <linux/list.h>
>  #include <linux/of.h>
>  #include <linux/of_address.h>
>  #include <linux/of_platform.h>
> @@ -22,31 +23,94 @@
>  #include <linux/platform_device.h>
>  #include <linux/regmap.h>
>  #include <linux/mfd/syscon.h>
> +#include <linux/slab.h>
>  
>  static struct platform_driver syscon_driver;
>  
> +static DEFINE_SPINLOCK(syscon_list_slock);
> +static LIST_HEAD(syscon_list);
> +
>  struct syscon {
> +	struct device_node *np;
>  	struct regmap *regmap;
> +	struct list_head list;
> +};
> +
> +static struct regmap_config syscon_regmap_config = {
> +	.reg_bits = 32,
> +	.val_bits = 32,
> +	.reg_stride = 4,
>  };
>  
> -static int syscon_match_node(struct device *dev, void *data)
> +static struct syscon *of_syscon_register(struct device_node *np)
>  {
> -	struct device_node *dn = data;
> +	struct syscon *syscon;
> +	struct regmap *regmap;
> +	void __iomem *base;
> +	int ret;
> +	struct regmap_config syscon_config = syscon_regmap_config;
> +
> +	if (!of_device_is_compatible(np, "syscon"))
> +		return ERR_PTR(-EINVAL);
> +
> +	syscon = kzalloc(sizeof(*syscon), GFP_KERNEL);
> +	if (!syscon)
> +		return ERR_PTR(-ENOMEM);
> +
> +	base = of_iomap(np, 0);
> +	if (!base) {
> +		ret = -ENOMEM;
> +		goto err_map;
> +	}
> +
> +	/* Parse the device's DT node for an endianness specification */
> +	if (of_property_read_bool(np, "big-endian"))
> +		syscon_config.val_format_endian = REGMAP_ENDIAN_BIG;
> +	 else if (of_property_read_bool(np, "little-endian"))
> +		syscon_config.val_format_endian = REGMAP_ENDIAN_LITTLE;
> +
> +	regmap = regmap_init_mmio(NULL, base, &syscon_config);
> +	if (IS_ERR(regmap)) {
> +		pr_err("regmap init failed\n");
> +		ret = PTR_ERR(regmap);
> +		goto err_regmap;
> +	}
> +
> +	syscon->regmap = regmap;
> +	syscon->np = np;
> +
> +	spin_lock(&syscon_list_slock);
> +	list_add_tail(&syscon->list, &syscon_list);
> +	spin_unlock(&syscon_list_slock);
>  
> -	return (dev->of_node == dn) ? 1 : 0;
> +	return syscon;
> +
> +err_regmap:
> +	iounmap(base);
> +err_map:
> +	kfree(syscon);
> +	return ERR_PTR(ret);
>  }
>  
>  struct regmap *syscon_node_to_regmap(struct device_node *np)
>  {
> -	struct syscon *syscon;
> -	struct device *dev;
> +	struct syscon *entry, *syscon = NULL;
>  
> -	dev = driver_find_device(&syscon_driver.driver, NULL, np,
> -				 syscon_match_node);
> -	if (!dev)
> -		return ERR_PTR(-EPROBE_DEFER);
> +	spin_lock(&syscon_list_slock);
>  
> -	syscon = dev_get_drvdata(dev);
> +	list_for_each_entry(entry, &syscon_list, list)
> +		if (entry->np == np) {
> +			syscon = entry;
> +			break;
> +		}
> +
> +	spin_unlock(&syscon_list_slock);
> +
> +	if (!syscon)
> +		syscon = of_syscon_register(np);
> +
> +	if (IS_ERR(syscon))
> +		return ERR_CAST(syscon);
>  
>  	return syscon->regmap;
>  }
> @@ -110,17 +174,6 @@ struct regmap *syscon_regmap_lookup_by_phandle(struct device_node *np,
>  }
>  EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_phandle);
>  
> -static const struct of_device_id of_syscon_match[] = {
> -	{ .compatible = "syscon", },
> -	{ },
> -};
> -
> -static struct regmap_config syscon_regmap_config = {
> -	.reg_bits = 32,
> -	.val_bits = 32,
> -	.reg_stride = 4,
> -};
> -
>  static int syscon_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
> @@ -167,7 +220,6 @@ static struct platform_driver syscon_driver = {
>  	.driver = {
>  		.name = "syscon",
>  		.owner = THIS_MODULE,
> -		.of_match_table = of_syscon_match,
>  	},
>  	.probe		= syscon_probe,
>  	.id_table	= syscon_ids,

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

RE: [PATCH v7] mfd: syscon: Decouple syscon interface from platform devices

[Pankaj Dubey]

Hello Lee,

On Tuesday, October 07, 2014 2:39 PM, Lee Jones wrote,
> On Tue, 30 Sep 2014, Pankaj Dubey wrote:
> 
> > Currently a syscon entity can be only registered directly through a
> > platform device that binds to a dedicated syscon driver. However in
> > certain use cases it is desirable to make a device used with another
> > driver a syscon interface provider.
> >
> > For example, certain SoCs (e.g. Exynos) contain system controller
> > blocks which perform various functions such as power domain control,
> > CPU power management, low power mode control, but in addition contain
> > certain IP integration glue, such as various signal masks, coprocessor
> > power control, etc. In such case, there is a need to have a dedicated
> > driver for such system controller but also share registers with other
> > drivers. The latter is where the syscon interface is helpful.
> >
> > In case of DT based platforms, this patch decouples syscon object from
> > syscon platform driver, and allows to create syscon objects first time
> > when it is required by calling of syscon_regmap_lookup_by APIs and
> > keep a list of such syscon objects along with syscon provider
> > device_nodes and regmap handles.
> >
> > For non-DT based platforms, this patch keeps syscon platform driver
> > structure so that syscon can be probed and such non-DT based drivers
> > can use syscon_regmap_lookup_by_pdev API and access regmap handles.
> > Once all users of "syscon_regmap_lookup_by_pdev" migrated to DT based,
> > we can completely remove platform driver of syscon, and keep only
> > helper functions to get regmap handles.
> >
> > Suggested-by: Arnd Bergmann <arnd@arndb.de>
> > Suggested-by: Tomasz Figa <tomasz.figa@gmail.com>
> > Tested-by: Vivek Gautam <gautam.vivek@samsung.com>
> > Tested-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
> > Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> > Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> > Tested-by: Heiko Stuebner <heiko@sntech.de>
> > Reviewed-by: Heiko Stuebner <heiko@sntech.de>
> 
> Applied for v3.19.

I can't see this in 3.18-rc1, as this patch is one of dependency for many of Exynos PMU related patches,
will you please queue this patch for 3.18-rc2, so that already ready to be in patches having this patch as
dependency can be taken in.

Thanks,
Pankaj Dubey
> 
> --
> Lee Jones
> Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software
> for ARM SoCs Follow Linaro: Facebook | Twitter | Blog

Re: [PATCH v7] mfd: syscon: Decouple syscon interface from platform devices

[Lee Jones]

On Wed, 22 Oct 2014, Pankaj Dubey wrote:

> Hello Lee,
> 
> On Tuesday, October 07, 2014 2:39 PM, Lee Jones wrote,
> > On Tue, 30 Sep 2014, Pankaj Dubey wrote:
> > 
> > > Currently a syscon entity can be only registered directly through a
> > > platform device that binds to a dedicated syscon driver. However in
> > > certain use cases it is desirable to make a device used with another
> > > driver a syscon interface provider.
> > >
> > > For example, certain SoCs (e.g. Exynos) contain system controller
> > > blocks which perform various functions such as power domain control,
> > > CPU power management, low power mode control, but in addition contain
> > > certain IP integration glue, such as various signal masks, coprocessor
> > > power control, etc. In such case, there is a need to have a dedicated
> > > driver for such system controller but also share registers with other
> > > drivers. The latter is where the syscon interface is helpful.
> > >
> > > In case of DT based platforms, this patch decouples syscon object from
> > > syscon platform driver, and allows to create syscon objects first time
> > > when it is required by calling of syscon_regmap_lookup_by APIs and
> > > keep a list of such syscon objects along with syscon provider
> > > device_nodes and regmap handles.
> > >
> > > For non-DT based platforms, this patch keeps syscon platform driver
> > > structure so that syscon can be probed and such non-DT based drivers
> > > can use syscon_regmap_lookup_by_pdev API and access regmap handles.
> > > Once all users of "syscon_regmap_lookup_by_pdev" migrated to DT based,
> > > we can completely remove platform driver of syscon, and keep only
> > > helper functions to get regmap handles.
> > >
> > > Suggested-by: Arnd Bergmann <arnd@arndb.de>
> > > Suggested-by: Tomasz Figa <tomasz.figa@gmail.com>
> > > Tested-by: Vivek Gautam <gautam.vivek@samsung.com>
> > > Tested-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
> > > Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
> > > Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> > > Tested-by: Heiko Stuebner <heiko@sntech.de>
> > > Reviewed-by: Heiko Stuebner <heiko@sntech.de>
> > 
> > Applied for v3.19.
> 
> I can't see this in 3.18-rc1, as this patch is one of dependency for many of Exynos PMU related patches,
> will you please queue this patch for 3.18-rc2, so that already ready to be in patches having this patch as
> dependency can be taken in.

As my message implies, this isn't going to make it into v3.18 but it
is queued for v3.19.  It was sent far too late in the cycle (rc7 of 7)
to make it into the v3.18 merge-window.

In the meantime, please give this patch through testing whilst it's in
-next, to help mitigate any issues when it's applied into v3.19.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog