[PATCH v3] mfd: syscon: Decouple syscon interface from platform devices

[...]

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   create child: /dcsr at 20000000/dcsr-atbrepl at 3a8000
   create child: /dcsr at 20000000/dcsr-tsgen-ctrl at 3a9000
   create child: /dcsr at 20000000/dcsr-tsgen-read at 3aa000
   create child: /regulators/regulator at 0
   ...

As default the Linux will create all the platform device for each DT node,

which

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Can be found from "drivers/of/platform.c".

So we can get the pdev node using the specified DT node, and feel safe to

use

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it as Pankaj's patch does.

I mean before the devices are populated from device tree.
For example, we usually call of_platform_populate in .init_machine.
Before it, we may not be able to get it's device, isn't it?

Yes, right.

For this case, we'd better create the pdev or dev manually for the first time
We use it, right ?

Thanks,

BRs
Xiubo

Regards
Dong Aisheng

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And also we must make sure that the 'syscon' DT nodes has the compatible

prop.

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Thanks,

BRs
Xiubo

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Regards
Dong Aisheng

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----
static struct syscon *of_syscon_register(struct device_node *np)
 {
+	struct platform_device *pdev;
 	struct syscon *syscon;
 	struct regmap *regmap;
 	void __iomem *base;

@@ -142,7 +144,11 @@ static struct syscon *of_syscon_register(struct

device_node *np)
 	if (!base)
 		return ERR_PTR(-ENOMEM);

-	regmap = regmap_init_mmio(NULL, base, &syscon_regmap_config);
+	pdev = of_find_device_by_node(np);
+	if (!(&pdev->dev))
+		return ERR_PTR(-ENODEV);
+
+	regmap = regmap_init_mmio(&pdev->dev, base,

&syscon_regmap_config);

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 	if (IS_ERR(regmap)) {
 		pr_err("regmap init failed\n");
 		return ERR_CAST(regmap);
-------

I have tested this in linux-next and it works well. In this way there

won't

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be any issues of
dereferencing NULL pointer in regmap.c and at the same time, if DT has
{big,little}-endian
optional property in syscon device node, it will be taken care.

So I would wait for Arnd's opinion about above mentioned changes and

then

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post a new
change after addressing Arnd's minor comment along with this fix in next
revision.


Thanks,
Pankaj Dubey

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Maybe we could consider create device structure for each syscon

compatible

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device in

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syscon driver in of_syscon_register in first time which seems to be

reasonable.

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Regards
Dong Aisheng

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--------------------------------------------
Subject: [PATCH] regmap: fix NULL pointer dereference in
regmap_get_val_endian

Recent commits for getting reg endianess causing NULL pointer
dereference if dev is passed NULL in regmap_init_mmio. This patch
fixes this issue, and allows to parse reg endianess only if dev and
dev->of_node exist.

Signed-off-by: Pankaj Dubey <redacted>
---
 drivers/base/regmap/regmap.c |   23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/base/regmap/regmap.c

b/drivers/base/regmap/regmap.c index f2281af..455a877 100644

--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c

@@ -477,7 +477,7 @@ static enum regmap_endian

regmap_get_val_endian(struct device *dev,
 					const struct regmap_bus *bus,
 					const struct regmap_config *config)

{

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-	struct device_node *np = dev->of_node;
+	struct device_node *np;
 	enum regmap_endian endian;

 	/* Retrieve the endianness specification from the regmap config

*/

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@@ -487,15 +487,20 @@ static enum regmap_endian

regmap_get_val_endian(struct device *dev,
 	if (endian != REGMAP_ENDIAN_DEFAULT)
 		return endian;

-	/* Parse the device's DT node for an endianness specification */
-	if (of_property_read_bool(np, "big-endian"))
-		endian = REGMAP_ENDIAN_BIG;
-	else if (of_property_read_bool(np, "little-endian"))
-		endian = REGMAP_ENDIAN_LITTLE;
+	/* If the dev and dev->of_node exist try to get endianness from

DT

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*/
+	if (dev && dev->of_node) {
+		np = dev->of_node;

-	/* If the endianness was specified in DT, use that */
-	if (endian != REGMAP_ENDIAN_DEFAULT)
-		return endian;
+		/* Parse the device's DT node for an endianness
specification */
+		if (of_property_read_bool(np, "big-endian"))
+			endian = REGMAP_ENDIAN_BIG;
+		else if (of_property_read_bool(np, "little-endian"))
+			endian = REGMAP_ENDIAN_LITTLE;
+
+		/* If the endianness was specified in DT, use that */
+		if (endian != REGMAP_ENDIAN_DEFAULT)
+			return endian;
+	}

 	/* Retrieve the endianness specification from the bus config */
 	if (bus && bus->val_format_endian_default)
--

Thanks,
Pankaj Dubey

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Regards
Dong Aisheng

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Thanks,
Pankaj Dubey

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Regards
Dong Aisheng

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