[PATCH 1/2] soc: imx: gpcv2: Do not pass static memory as platform data

[PATCH 1/2] soc: imx: gpcv2: Do not pass static memory as platform data

[Andrey Smirnov]

Platform device core assumes the ownership of dev.platform_data as
well as that it is dynamically allocated and it will try to kfree it
as a part of platform_device_release(). Change the code to pass
kzalloc'ed chunk of memory instead of a pointer to a static memory to
avoid causing a BUG() when calling platform_device_put().

The problem can be reproduced by artificially enabling the error path
of platform_device_add() call (around line 357).

Note that this change also allows us to constify imx7_pgc_domains,
since we no longer need to be able to modify it.

Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
---

This patch is a follow up to fix one of the bugs discussed in
lkml.kernel.org/r/3f836677c6e98aaf01bc1ac8c3410083@agner.ch

 drivers/soc/imx/gpcv2.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/soc/imx/gpcv2.c b/drivers/soc/imx/gpcv2.c
index afc7ecc3c187..001b64afa5c1 100644
--- a/drivers/soc/imx/gpcv2.c
+++ b/drivers/soc/imx/gpcv2.c
@@ -18,6 +18,7 @@
 #include <linux/pm_domain.h>
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
+#include <linux/slab.h>
 #include <dt-bindings/power/imx7-power.h>
 
 #define GPC_LPCR_A7_BSC			0x000
@@ -155,7 +156,7 @@ static int imx7_gpc_pu_pgc_sw_pdn_req(struct generic_pm_domain *genpd)
 	return imx7_gpc_pu_pgc_sw_pxx_req(genpd, false);
 }
 
-static struct imx7_pgc_domain imx7_pgc_domains[] = {
+static const struct imx7_pgc_domain imx7_pgc_domains[] = {
 	[IMX7_POWER_DOMAIN_MIPI_PHY] = {
 		.genpd = {
 			.name      = "mipi-phy",
@@ -321,7 +322,14 @@ static int imx_gpcv2_probe(struct platform_device *pdev)
 			continue;
 		}
 
-		domain = &imx7_pgc_domains[domain_index];
+		domain = kzalloc(sizeof(*domain), GFP_KERNEL);
+		if (!domain) {
+			of_node_put(np);
+			return -ENOMEM;
+		}
+		memcpy(domain, &imx7_pgc_domains[domain_index],
+		       sizeof(*domain));
+
 		domain->regmap = regmap;
 		domain->genpd.power_on  = imx7_gpc_pu_pgc_sw_pup_req;
 		domain->genpd.power_off = imx7_gpc_pu_pgc_sw_pdn_req;
@@ -330,6 +338,7 @@ static int imx_gpcv2_probe(struct platform_device *pdev)
 						domain_index);
 		if (!pd_pdev) {
 			dev_err(dev, "Failed to allocate platform device\n");
+			kfree(domain);
 			of_node_put(np);
 			return -ENOMEM;
 		}
-- 
2.14.3

[PATCH 1/2] soc: imx: gpcv2: Do not pass static memory as platform data

[Andrey Smirnov]

Platform device core assumes the ownership of dev.platform_data as
well as that it is dynamically allocated and it will try to kfree it
as a part of platform_device_release(). Change the code to pass
kzalloc'ed chunk of memory instead of a pointer to a static memory to
avoid causing a BUG() when calling platform_device_put().

The problem can be reproduced by artificially enabling the error path
of platform_device_add() call (around line 357).

Note that this change also allows us to constify imx7_pgc_domains,
since we no longer need to be able to modify it.

Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-kernel at vger.kernel.org
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
---

This patch is a follow up to fix one of the bugs discussed in
lkml.kernel.org/r/3f836677c6e98aaf01bc1ac8c3410083 at agner.ch

 drivers/soc/imx/gpcv2.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/soc/imx/gpcv2.c b/drivers/soc/imx/gpcv2.c
index afc7ecc3c187..001b64afa5c1 100644
--- a/drivers/soc/imx/gpcv2.c
+++ b/drivers/soc/imx/gpcv2.c
@@ -18,6 +18,7 @@
 #include <linux/pm_domain.h>
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
+#include <linux/slab.h>
 #include <dt-bindings/power/imx7-power.h>
 
 #define GPC_LPCR_A7_BSC			0x000
@@ -155,7 +156,7 @@ static int imx7_gpc_pu_pgc_sw_pdn_req(struct generic_pm_domain *genpd)
 	return imx7_gpc_pu_pgc_sw_pxx_req(genpd, false);
 }
 
-static struct imx7_pgc_domain imx7_pgc_domains[] = {
+static const struct imx7_pgc_domain imx7_pgc_domains[] = {
 	[IMX7_POWER_DOMAIN_MIPI_PHY] = {
 		.genpd = {
 			.name      = "mipi-phy",
@@ -321,7 +322,14 @@ static int imx_gpcv2_probe(struct platform_device *pdev)
 			continue;
 		}
 
-		domain = &imx7_pgc_domains[domain_index];
+		domain = kzalloc(sizeof(*domain), GFP_KERNEL);
+		if (!domain) {
+			of_node_put(np);
+			return -ENOMEM;
+		}
+		memcpy(domain, &imx7_pgc_domains[domain_index],
+		       sizeof(*domain));
+
 		domain->regmap = regmap;
 		domain->genpd.power_on  = imx7_gpc_pu_pgc_sw_pup_req;
 		domain->genpd.power_off = imx7_gpc_pu_pgc_sw_pdn_req;
@@ -330,6 +338,7 @@ static int imx_gpcv2_probe(struct platform_device *pdev)
 						domain_index);
 		if (!pd_pdev) {
 			dev_err(dev, "Failed to allocate platform device\n");
+			kfree(domain);
 			of_node_put(np);
 			return -ENOMEM;
 		}
-- 
2.14.3

[PATCH 2/2] soc: imx: gpc: Do not pass static memory as platform data

[Andrey Smirnov]

Platform device core assumes the ownership of dev.platform_data as
well as that it is dynamically allocated and it will try to kfree it
as a part of platform_device_release(). Change the code to pass
kzalloc'ed chunk of memory instead of a pointer to a static memory to
avoid causing a BUG() when calling platform_device_put().

The problem can be reproduced by artificially enabling the error path
of platform_device_add() call (around line 452).

Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
---

This patch is a follow up to fix one of the bugs discussed in
lkml.kernel.org/r/3f836677c6e98aaf01bc1ac8c3410083@agner.ch

 drivers/soc/imx/gpc.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/soc/imx/gpc.c b/drivers/soc/imx/gpc.c
index 47e7aa963dbb..ec8b79abebac 100644
--- a/drivers/soc/imx/gpc.c
+++ b/drivers/soc/imx/gpc.c
@@ -18,6 +18,7 @@
 #include <linux/pm_domain.h>
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
+#include <linux/slab.h>
 
 #define GPC_CNTR		0x000
 
@@ -428,13 +429,19 @@ static int imx_gpc_probe(struct platform_device *pdev)
 			if (domain_index >= of_id_data->num_domains)
 				continue;
 
-			domain = &imx_gpc_domains[domain_index];
+			domain = kzalloc(sizeof(*domain), GFP_KERNEL);
+			if (!domain) {
+				of_node_put(np);
+				return -ENOMEM;
+			}
+			memcpy(domain, &imx_gpc_domains[domain_index], sizeof(*domain));
 			domain->regmap = regmap;
 			domain->ipg_rate_mhz = ipg_rate_mhz;
 
 			pd_pdev = platform_device_alloc("imx-pgc-power-domain",
 							domain_index);
 			if (!pd_pdev) {
+				kfree(domain);
 				of_node_put(np);
 				return -ENOMEM;
 			}
-- 
2.14.3

[PATCH 2/2] soc: imx: gpc: Do not pass static memory as platform data

[Andrey Smirnov]

Platform device core assumes the ownership of dev.platform_data as
well as that it is dynamically allocated and it will try to kfree it
as a part of platform_device_release(). Change the code to pass
kzalloc'ed chunk of memory instead of a pointer to a static memory to
avoid causing a BUG() when calling platform_device_put().

The problem can be reproduced by artificially enabling the error path
of platform_device_add() call (around line 452).

Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-kernel at vger.kernel.org
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
---

This patch is a follow up to fix one of the bugs discussed in
lkml.kernel.org/r/3f836677c6e98aaf01bc1ac8c3410083 at agner.ch

 drivers/soc/imx/gpc.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/soc/imx/gpc.c b/drivers/soc/imx/gpc.c
index 47e7aa963dbb..ec8b79abebac 100644
--- a/drivers/soc/imx/gpc.c
+++ b/drivers/soc/imx/gpc.c
@@ -18,6 +18,7 @@
 #include <linux/pm_domain.h>
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
+#include <linux/slab.h>
 
 #define GPC_CNTR		0x000
 
@@ -428,13 +429,19 @@ static int imx_gpc_probe(struct platform_device *pdev)
 			if (domain_index >= of_id_data->num_domains)
 				continue;
 
-			domain = &imx_gpc_domains[domain_index];
+			domain = kzalloc(sizeof(*domain), GFP_KERNEL);
+			if (!domain) {
+				of_node_put(np);
+				return -ENOMEM;
+			}
+			memcpy(domain, &imx_gpc_domains[domain_index], sizeof(*domain));
 			domain->regmap = regmap;
 			domain->ipg_rate_mhz = ipg_rate_mhz;
 
 			pd_pdev = platform_device_alloc("imx-pgc-power-domain",
 							domain_index);
 			if (!pd_pdev) {
+				kfree(domain);
 				of_node_put(np);
 				return -ENOMEM;
 			}
-- 
2.14.3

Re: [PATCH 2/2] soc: imx: gpc: Do not pass static memory as platform data

[Stefan Agner]

On 2018-01-10 17:16, Andrey Smirnov wrote:
> Platform device core assumes the ownership of dev.platform_data as
> well as that it is dynamically allocated and it will try to kfree it
> as a part of platform_device_release(). Change the code to pass
> kzalloc'ed chunk of memory instead of a pointer to a static memory to
> avoid causing a BUG() when calling platform_device_put().

I tried to get around that by setting platform_data to null before
unregistring the device, see:
https://marc.info/?l=linux-arm-kernel&m=151553216030129&w=2


This solutions still seems to miss unregistering the platform devices,
which shows when binding the driver again:

root@colibri-imx6:~# echo 20dc000.gpc >
/sys/bus/platform/drivers/imx-gpc/unbind 
[   80.702627] imx-pgc-pd imx-pgc-power-domain.0: Dropping the link to
20dc000.gpc
[   80.710808] genpd_remove: unable to remove PU
[   80.716408] imx-pgc-pd imx-pgc-power-domain.1: Dropping the link to
20dc000.gpc
root@colibri-imx6:~# find /sys -name *pgc-power*
/sys/devices/soc0/soc/2000000.aips-bus/20dc000.gpc/imx-pgc-power-domain.0
/sys/devices/soc0/soc/2000000.aips-bus/20dc000.gpc/imx-pgc-power-domain.1
/sys/bus/platform/devices/imx-pgc-power-domain.0
/sys/bus/platform/devices/imx-pgc-power-domain.1
root@colibri-imx6:~# echo 20dc000.gpc >
/sys/bus/platform/drivers/imx-gpc/bind 
[   89.002754] ------------[ cut here ]------------
[   89.007411] WARNING: CPU: 0 PID: 516 at fs/sysfs/dir.c:31
sysfs_warn_dup+0x64/0x74
[   89.015057] sysfs: cannot create duplicate filename
'/devices/soc0/soc/2000000.aips-bus/20dc000.gpc/imx-pgc-power-domain.0'


> 
> The problem can be reproduced by artificially enabling the error path
> of platform_device_add() call (around line 452).
> 
> Cc: Shawn Guo <shawnguo@kernel.org>
> Cc: Stefan Agner <stefan@agner.ch>
> Cc: Lucas Stach <l.stach@pengutronix.de>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
> ---
> 
> This patch is a follow up to fix one of the bugs discussed in
> lkml.kernel.org/r/3f836677c6e98aaf01bc1ac8c3410083@agner.ch
> 
>  drivers/soc/imx/gpc.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/soc/imx/gpc.c b/drivers/soc/imx/gpc.c
> index 47e7aa963dbb..ec8b79abebac 100644
> --- a/drivers/soc/imx/gpc.c
> +++ b/drivers/soc/imx/gpc.c
> @@ -18,6 +18,7 @@
>  #include <linux/pm_domain.h>
>  #include <linux/regmap.h>
>  #include <linux/regulator/consumer.h>
> +#include <linux/slab.h>
>  
>  #define GPC_CNTR		0x000
>  
> @@ -428,13 +429,19 @@ static int imx_gpc_probe(struct platform_device *pdev)
>  			if (domain_index >= of_id_data->num_domains)
>  				continue;
>  
> -			domain = &imx_gpc_domains[domain_index];
> +			domain = kzalloc(sizeof(*domain), GFP_KERNEL);

I guess you could use just kalloc here since you memcpy below.

--
Stefan

> +			if (!domain) {
> +				of_node_put(np);
> +				return -ENOMEM;
> +			}
> +			memcpy(domain, &imx_gpc_domains[domain_index], sizeof(*domain));
>  			domain->regmap = regmap;
>  			domain->ipg_rate_mhz = ipg_rate_mhz;
>  
>  			pd_pdev = platform_device_alloc("imx-pgc-power-domain",
>  							domain_index);
>  			if (!pd_pdev) {
> +				kfree(domain);
>  				of_node_put(np);
>  				return -ENOMEM;
>  			}

[PATCH 2/2] soc: imx: gpc: Do not pass static memory as platform data

[Stefan Agner]

On 2018-01-10 17:16, Andrey Smirnov wrote:
> Platform device core assumes the ownership of dev.platform_data as
> well as that it is dynamically allocated and it will try to kfree it
> as a part of platform_device_release(). Change the code to pass
> kzalloc'ed chunk of memory instead of a pointer to a static memory to
> avoid causing a BUG() when calling platform_device_put().

I tried to get around that by setting platform_data to null before
unregistring the device, see:
https://marc.info/?l=linux-arm-kernel&m=151553216030129&w=2


This solutions still seems to miss unregistering the platform devices,
which shows when binding the driver again:

root at colibri-imx6:~# echo 20dc000.gpc >
/sys/bus/platform/drivers/imx-gpc/unbind 
[   80.702627] imx-pgc-pd imx-pgc-power-domain.0: Dropping the link to
20dc000.gpc
[   80.710808] genpd_remove: unable to remove PU
[   80.716408] imx-pgc-pd imx-pgc-power-domain.1: Dropping the link to
20dc000.gpc
root at colibri-imx6:~# find /sys -name *pgc-power*
/sys/devices/soc0/soc/2000000.aips-bus/20dc000.gpc/imx-pgc-power-domain.0
/sys/devices/soc0/soc/2000000.aips-bus/20dc000.gpc/imx-pgc-power-domain.1
/sys/bus/platform/devices/imx-pgc-power-domain.0
/sys/bus/platform/devices/imx-pgc-power-domain.1
root at colibri-imx6:~# echo 20dc000.gpc >
/sys/bus/platform/drivers/imx-gpc/bind 
[   89.002754] ------------[ cut here ]------------
[   89.007411] WARNING: CPU: 0 PID: 516 at fs/sysfs/dir.c:31
sysfs_warn_dup+0x64/0x74
[   89.015057] sysfs: cannot create duplicate filename
'/devices/soc0/soc/2000000.aips-bus/20dc000.gpc/imx-pgc-power-domain.0'


> 
> The problem can be reproduced by artificially enabling the error path
> of platform_device_add() call (around line 452).
> 
> Cc: Shawn Guo <shawnguo@kernel.org>
> Cc: Stefan Agner <stefan@agner.ch>
> Cc: Lucas Stach <l.stach@pengutronix.de>
> Cc: linux-arm-kernel at lists.infradead.org
> Cc: linux-kernel at vger.kernel.org
> Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
> ---
> 
> This patch is a follow up to fix one of the bugs discussed in
> lkml.kernel.org/r/3f836677c6e98aaf01bc1ac8c3410083 at agner.ch
> 
>  drivers/soc/imx/gpc.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/soc/imx/gpc.c b/drivers/soc/imx/gpc.c
> index 47e7aa963dbb..ec8b79abebac 100644
> --- a/drivers/soc/imx/gpc.c
> +++ b/drivers/soc/imx/gpc.c
> @@ -18,6 +18,7 @@
>  #include <linux/pm_domain.h>
>  #include <linux/regmap.h>
>  #include <linux/regulator/consumer.h>
> +#include <linux/slab.h>
>  
>  #define GPC_CNTR		0x000
>  
> @@ -428,13 +429,19 @@ static int imx_gpc_probe(struct platform_device *pdev)
>  			if (domain_index >= of_id_data->num_domains)
>  				continue;
>  
> -			domain = &imx_gpc_domains[domain_index];
> +			domain = kzalloc(sizeof(*domain), GFP_KERNEL);

I guess you could use just kalloc here since you memcpy below.

--
Stefan

> +			if (!domain) {
> +				of_node_put(np);
> +				return -ENOMEM;
> +			}
> +			memcpy(domain, &imx_gpc_domains[domain_index], sizeof(*domain));
>  			domain->regmap = regmap;
>  			domain->ipg_rate_mhz = ipg_rate_mhz;
>  
>  			pd_pdev = platform_device_alloc("imx-pgc-power-domain",
>  							domain_index);
>  			if (!pd_pdev) {
> +				kfree(domain);
>  				of_node_put(np);
>  				return -ENOMEM;
>  			}

Re: [PATCH 2/2] soc: imx: gpc: Do not pass static memory as platform data

[Andrey Smirnov]

On Wed, Jan 10, 2018 at 12:49 PM, Stefan Agner <stefan@agner.ch> wrote:
> On 2018-01-10 17:16, Andrey Smirnov wrote:
>> Platform device core assumes the ownership of dev.platform_data as
>> well as that it is dynamically allocated and it will try to kfree it
>> as a part of platform_device_release(). Change the code to pass
>> kzalloc'ed chunk of memory instead of a pointer to a static memory to
>> avoid causing a BUG() when calling platform_device_put().
>
> I tried to get around that by setting platform_data to null before
> unregistring the device, see:
> https://marc.info/?l=linux-arm-kernel&m=151553216030129&w=2
>

Sorry should've commented in that thread: I saw that in your code, but
it felt to me like playing with fire a bit. IMHO calling
platform_device_put() should just work and not depend on certain field
being set to NULL prior.

>
> This solutions still seems to miss unregistering the platform devices,
> which shows when binding the driver again:
>

Absolutely, this patch solves a problem, not the problem :-) I think
solving the problem is orthogonal to this and warrants a separate
patch.

> root@colibri-imx6:~# echo 20dc000.gpc >
> /sys/bus/platform/drivers/imx-gpc/unbind
> [   80.702627] imx-pgc-pd imx-pgc-power-domain.0: Dropping the link to
> 20dc000.gpc
> [   80.710808] genpd_remove: unable to remove PU
> [   80.716408] imx-pgc-pd imx-pgc-power-domain.1: Dropping the link to
> 20dc000.gpc
> root@colibri-imx6:~# find /sys -name *pgc-power*
> /sys/devices/soc0/soc/2000000.aips-bus/20dc000.gpc/imx-pgc-power-domain.0
> /sys/devices/soc0/soc/2000000.aips-bus/20dc000.gpc/imx-pgc-power-domain.1
> /sys/bus/platform/devices/imx-pgc-power-domain.0
> /sys/bus/platform/devices/imx-pgc-power-domain.1
> root@colibri-imx6:~# echo 20dc000.gpc >
> /sys/bus/platform/drivers/imx-gpc/bind
> [   89.002754] ------------[ cut here ]------------
> [   89.007411] WARNING: CPU: 0 PID: 516 at fs/sysfs/dir.c:31
> sysfs_warn_dup+0x64/0x74
> [   89.015057] sysfs: cannot create duplicate filename
> '/devices/soc0/soc/2000000.aips-bus/20dc000.gpc/imx-pgc-power-domain.0'
>
>
>>
>> The problem can be reproduced by artificially enabling the error path
>> of platform_device_add() call (around line 452).
>>
>> Cc: Shawn Guo <shawnguo@kernel.org>
>> Cc: Stefan Agner <stefan@agner.ch>
>> Cc: Lucas Stach <l.stach@pengutronix.de>
>> Cc: linux-arm-kernel@lists.infradead.org
>> Cc: linux-kernel@vger.kernel.org
>> Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
>> ---
>>
>> This patch is a follow up to fix one of the bugs discussed in
>> lkml.kernel.org/r/3f836677c6e98aaf01bc1ac8c3410083@agner.ch
>>
>>  drivers/soc/imx/gpc.c | 9 ++++++++-
>>  1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/soc/imx/gpc.c b/drivers/soc/imx/gpc.c
>> index 47e7aa963dbb..ec8b79abebac 100644
>> --- a/drivers/soc/imx/gpc.c
>> +++ b/drivers/soc/imx/gpc.c
>> @@ -18,6 +18,7 @@
>>  #include <linux/pm_domain.h>
>>  #include <linux/regmap.h>
>>  #include <linux/regulator/consumer.h>
>> +#include <linux/slab.h>
>>
>>  #define GPC_CNTR             0x000
>>
>> @@ -428,13 +429,19 @@ static int imx_gpc_probe(struct platform_device *pdev)
>>                       if (domain_index >= of_id_data->num_domains)
>>                               continue;
>>
>> -                     domain = &imx_gpc_domains[domain_index];
>> +                     domain = kzalloc(sizeof(*domain), GFP_KERNEL);
>
> I guess you could use just kalloc here since you memcpy below.
>

Good point. Will change in v2.

Thanks,
Andrey Smirnov

[PATCH 2/2] soc: imx: gpc: Do not pass static memory as platform data

[Andrey Smirnov]

On Wed, Jan 10, 2018 at 12:49 PM, Stefan Agner <stefan@agner.ch> wrote:
> On 2018-01-10 17:16, Andrey Smirnov wrote:
>> Platform device core assumes the ownership of dev.platform_data as
>> well as that it is dynamically allocated and it will try to kfree it
>> as a part of platform_device_release(). Change the code to pass
>> kzalloc'ed chunk of memory instead of a pointer to a static memory to
>> avoid causing a BUG() when calling platform_device_put().
>
> I tried to get around that by setting platform_data to null before
> unregistring the device, see:
> https://marc.info/?l=linux-arm-kernel&m=151553216030129&w=2
>

Sorry should've commented in that thread: I saw that in your code, but
it felt to me like playing with fire a bit. IMHO calling
platform_device_put() should just work and not depend on certain field
being set to NULL prior.

>
> This solutions still seems to miss unregistering the platform devices,
> which shows when binding the driver again:
>

Absolutely, this patch solves a problem, not the problem :-) I think
solving the problem is orthogonal to this and warrants a separate
patch.

> root at colibri-imx6:~# echo 20dc000.gpc >
> /sys/bus/platform/drivers/imx-gpc/unbind
> [   80.702627] imx-pgc-pd imx-pgc-power-domain.0: Dropping the link to
> 20dc000.gpc
> [   80.710808] genpd_remove: unable to remove PU
> [   80.716408] imx-pgc-pd imx-pgc-power-domain.1: Dropping the link to
> 20dc000.gpc
> root at colibri-imx6:~# find /sys -name *pgc-power*
> /sys/devices/soc0/soc/2000000.aips-bus/20dc000.gpc/imx-pgc-power-domain.0
> /sys/devices/soc0/soc/2000000.aips-bus/20dc000.gpc/imx-pgc-power-domain.1
> /sys/bus/platform/devices/imx-pgc-power-domain.0
> /sys/bus/platform/devices/imx-pgc-power-domain.1
> root at colibri-imx6:~# echo 20dc000.gpc >
> /sys/bus/platform/drivers/imx-gpc/bind
> [   89.002754] ------------[ cut here ]------------
> [   89.007411] WARNING: CPU: 0 PID: 516 at fs/sysfs/dir.c:31
> sysfs_warn_dup+0x64/0x74
> [   89.015057] sysfs: cannot create duplicate filename
> '/devices/soc0/soc/2000000.aips-bus/20dc000.gpc/imx-pgc-power-domain.0'
>
>
>>
>> The problem can be reproduced by artificially enabling the error path
>> of platform_device_add() call (around line 452).
>>
>> Cc: Shawn Guo <shawnguo@kernel.org>
>> Cc: Stefan Agner <stefan@agner.ch>
>> Cc: Lucas Stach <l.stach@pengutronix.de>
>> Cc: linux-arm-kernel at lists.infradead.org
>> Cc: linux-kernel at vger.kernel.org
>> Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
>> ---
>>
>> This patch is a follow up to fix one of the bugs discussed in
>> lkml.kernel.org/r/3f836677c6e98aaf01bc1ac8c3410083 at agner.ch
>>
>>  drivers/soc/imx/gpc.c | 9 ++++++++-
>>  1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/soc/imx/gpc.c b/drivers/soc/imx/gpc.c
>> index 47e7aa963dbb..ec8b79abebac 100644
>> --- a/drivers/soc/imx/gpc.c
>> +++ b/drivers/soc/imx/gpc.c
>> @@ -18,6 +18,7 @@
>>  #include <linux/pm_domain.h>
>>  #include <linux/regmap.h>
>>  #include <linux/regulator/consumer.h>
>> +#include <linux/slab.h>
>>
>>  #define GPC_CNTR             0x000
>>
>> @@ -428,13 +429,19 @@ static int imx_gpc_probe(struct platform_device *pdev)
>>                       if (domain_index >= of_id_data->num_domains)
>>                               continue;
>>
>> -                     domain = &imx_gpc_domains[domain_index];
>> +                     domain = kzalloc(sizeof(*domain), GFP_KERNEL);
>
> I guess you could use just kalloc here since you memcpy below.
>

Good point. Will change in v2.

Thanks,
Andrey Smirnov