[PATCH net 0/2] net: fixes for fec ptp

[PATCH net 0/2] net: fixes for fec ptp

[Joakim Zhang]

Small fixes for fec ptp.

Fugang Duan (1):
  net: fec_ptp: add clock rate zero check

Joakim Zhang (1):
  net: fec_ptp: fix issue caused by refactor the fec_devtype

 drivers/net/ethernet/freescale/fec_ptp.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

-- 
2.17.1

[PATCH net 0/2] net: fixes for fec ptp

[Joakim Zhang]

Small fixes for fec ptp.

Fugang Duan (1):
  net: fec_ptp: add clock rate zero check

Joakim Zhang (1):
  net: fec_ptp: fix issue caused by refactor the fec_devtype

 drivers/net/ethernet/freescale/fec_ptp.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

-- 
2.17.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH net 1/2] net: fec_ptp: add clock rate zero check

[Joakim Zhang]

From: Fugang Duan <fugang.duan@nxp.com>

Add clock rate zero check to fix coverity issue of "divide by 0".

Fixes: commit 85bd1798b24a ("net: fec: fix spin_lock dead lock")
Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
---
 drivers/net/ethernet/freescale/fec_ptp.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/freescale/fec_ptp.c b/drivers/net/ethernet/freescale/fec_ptp.c
index 1753807cbf97..7326a0612823 100644
--- a/drivers/net/ethernet/freescale/fec_ptp.c
+++ b/drivers/net/ethernet/freescale/fec_ptp.c
@@ -604,6 +604,10 @@ void fec_ptp_init(struct platform_device *pdev, int irq_idx)
 	fep->ptp_caps.enable = fec_ptp_enable;
 
 	fep->cycle_speed = clk_get_rate(fep->clk_ptp);
+	if (!fep->cycle_speed) {
+		fep->cycle_speed = NSEC_PER_SEC;
+		dev_err(&fep->pdev->dev, "clk_ptp clock rate is zero\n");
+	}
 	fep->ptp_inc = NSEC_PER_SEC / fep->cycle_speed;
 
 	spin_lock_init(&fep->tmreg_lock);
-- 
2.17.1

[PATCH net 1/2] net: fec_ptp: add clock rate zero check

[Joakim Zhang]

From: Fugang Duan <fugang.duan@nxp.com>

Add clock rate zero check to fix coverity issue of "divide by 0".

Fixes: commit 85bd1798b24a ("net: fec: fix spin_lock dead lock")
Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
---
 drivers/net/ethernet/freescale/fec_ptp.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/freescale/fec_ptp.c b/drivers/net/ethernet/freescale/fec_ptp.c
index 1753807cbf97..7326a0612823 100644
--- a/drivers/net/ethernet/freescale/fec_ptp.c
+++ b/drivers/net/ethernet/freescale/fec_ptp.c
@@ -604,6 +604,10 @@ void fec_ptp_init(struct platform_device *pdev, int irq_idx)
 	fep->ptp_caps.enable = fec_ptp_enable;
 
 	fep->cycle_speed = clk_get_rate(fep->clk_ptp);
+	if (!fep->cycle_speed) {
+		fep->cycle_speed = NSEC_PER_SEC;
+		dev_err(&fep->pdev->dev, "clk_ptp clock rate is zero\n");
+	}
 	fep->ptp_inc = NSEC_PER_SEC / fep->cycle_speed;
 
 	spin_lock_init(&fep->tmreg_lock);
-- 
2.17.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH net 1/2] net: fec_ptp: add clock rate zero check

[Russell King (Oracle)]

On Wed, Jun 16, 2021 at 05:14:25PM +0800, Joakim Zhang wrote:
> From: Fugang Duan <fugang.duan@nxp.com>
> 
> Add clock rate zero check to fix coverity issue of "divide by 0".
> 
> Fixes: commit 85bd1798b24a ("net: fec: fix spin_lock dead lock")
> Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
> Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
> ---
>  drivers/net/ethernet/freescale/fec_ptp.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/net/ethernet/freescale/fec_ptp.c b/drivers/net/ethernet/freescale/fec_ptp.c
> index 1753807cbf97..7326a0612823 100644
> --- a/drivers/net/ethernet/freescale/fec_ptp.c
> +++ b/drivers/net/ethernet/freescale/fec_ptp.c
> @@ -604,6 +604,10 @@ void fec_ptp_init(struct platform_device *pdev, int irq_idx)
>  	fep->ptp_caps.enable = fec_ptp_enable;
>  
>  	fep->cycle_speed = clk_get_rate(fep->clk_ptp);
> +	if (!fep->cycle_speed) {
> +		fep->cycle_speed = NSEC_PER_SEC;
> +		dev_err(&fep->pdev->dev, "clk_ptp clock rate is zero\n");

If this is supposed to be an error message, it doesn't convey that
something is really wrong to the user. Maybe something like this would
be more meaningful to the user:

	"PTP clock rate should not be zero, using 1GHz instead. PTP
	clock may be unreliable.\n"

It may be appropriate not to publish PTP support for the interface if
we don't have a valid clock rate, which is probably the safer approach
and would probably make the problem more noticable to the end user so
it gets fixed.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

Re: [PATCH net 1/2] net: fec_ptp: add clock rate zero check

[Russell King (Oracle)]

On Wed, Jun 16, 2021 at 05:14:25PM +0800, Joakim Zhang wrote:
> From: Fugang Duan <fugang.duan@nxp.com>
> 
> Add clock rate zero check to fix coverity issue of "divide by 0".
> 
> Fixes: commit 85bd1798b24a ("net: fec: fix spin_lock dead lock")
> Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
> Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
> ---
>  drivers/net/ethernet/freescale/fec_ptp.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/net/ethernet/freescale/fec_ptp.c b/drivers/net/ethernet/freescale/fec_ptp.c
> index 1753807cbf97..7326a0612823 100644
> --- a/drivers/net/ethernet/freescale/fec_ptp.c
> +++ b/drivers/net/ethernet/freescale/fec_ptp.c
> @@ -604,6 +604,10 @@ void fec_ptp_init(struct platform_device *pdev, int irq_idx)
>  	fep->ptp_caps.enable = fec_ptp_enable;
>  
>  	fep->cycle_speed = clk_get_rate(fep->clk_ptp);
> +	if (!fep->cycle_speed) {
> +		fep->cycle_speed = NSEC_PER_SEC;
> +		dev_err(&fep->pdev->dev, "clk_ptp clock rate is zero\n");

If this is supposed to be an error message, it doesn't convey that
something is really wrong to the user. Maybe something like this would
be more meaningful to the user:

	"PTP clock rate should not be zero, using 1GHz instead. PTP
	clock may be unreliable.\n"

It may be appropriate not to publish PTP support for the interface if
we don't have a valid clock rate, which is probably the safer approach
and would probably make the problem more noticable to the end user so
it gets fixed.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

RE: [PATCH net 1/2] net: fec_ptp: add clock rate zero check

[Joakim Zhang]

Hi Russell,

> -----Original Message-----
> From: Russell King <linux@armlinux.org.uk>
> Sent: 2021年6月16日 18:21
> To: Joakim Zhang <qiangqing.zhang@nxp.com>
> Cc: davem@davemloft.net; kuba@kernel.org; peppe.cavallaro@st.com;
> alexandre.torgue@foss.st.com; joabreu@synopsys.com;
> mcoquelin.stm32@gmail.com; netdev@vger.kernel.org;
> linux-kernel@vger.kernel.org; linux-stm32@st-md-mailman.stormreply.com;
> linux-arm-kernel@lists.infradead.org; dl-linux-imx <linux-imx@nxp.com>
> Subject: Re: [PATCH net 1/2] net: fec_ptp: add clock rate zero check
> 
> On Wed, Jun 16, 2021 at 05:14:25PM +0800, Joakim Zhang wrote:
> > From: Fugang Duan <fugang.duan@nxp.com>
> >
> > Add clock rate zero check to fix coverity issue of "divide by 0".
> >
> > Fixes: commit 85bd1798b24a ("net: fec: fix spin_lock dead lock")
> > Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
> > Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
> > ---
> >  drivers/net/ethernet/freescale/fec_ptp.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/freescale/fec_ptp.c
> > b/drivers/net/ethernet/freescale/fec_ptp.c
> > index 1753807cbf97..7326a0612823 100644
> > --- a/drivers/net/ethernet/freescale/fec_ptp.c
> > +++ b/drivers/net/ethernet/freescale/fec_ptp.c
> > @@ -604,6 +604,10 @@ void fec_ptp_init(struct platform_device *pdev, int
> irq_idx)
> >  	fep->ptp_caps.enable = fec_ptp_enable;
> >
> >  	fep->cycle_speed = clk_get_rate(fep->clk_ptp);
> > +	if (!fep->cycle_speed) {
> > +		fep->cycle_speed = NSEC_PER_SEC;
> > +		dev_err(&fep->pdev->dev, "clk_ptp clock rate is zero\n");
> 
> If this is supposed to be an error message, it doesn't convey that something is
> really wrong to the user. Maybe something like this would be more meaningful
> to the user:
> 
> 	"PTP clock rate should not be zero, using 1GHz instead. PTP
> 	clock may be unreliable.\n"
Make Sense.

> It may be appropriate not to publish PTP support for the interface if we don't
> have a valid clock rate, which is probably the safer approach and would
> probably make the problem more noticable to the end user so it gets fixed.

Do you mean that print an error message then return directly? It seems better.

if (!fep->cycle_speed) {
	dev_err(&fep->pdev->dev, "PTP clock rate should not be zero!\n");
	return;
}

Best Regards,
Joakim Zhang
> --
> RMK's Patch system:
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.ar
> mlinux.org.uk%2Fdeveloper%2Fpatches%2F&amp;data=04%7C01%7Cqiangqin
> g.zhang%40nxp.com%7Cb3c85322e359446e4eee08d930b06701%7C686ea1d3
> bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637594356476903644%7CUnknow
> n%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1ha
> WwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=TH4fZJRu8Ii6w7y05N8CHWoQR
> R9OegsYB7VAwgSpTcU%3D&amp;reserved=0
> FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

RE: [PATCH net 1/2] net: fec_ptp: add clock rate zero check

[Joakim Zhang]

Hi Russell,

> -----Original Message-----
> From: Russell King <linux@armlinux.org.uk>
> Sent: 2021年6月16日 18:21
> To: Joakim Zhang <qiangqing.zhang@nxp.com>
> Cc: davem@davemloft.net; kuba@kernel.org; peppe.cavallaro@st.com;
> alexandre.torgue@foss.st.com; joabreu@synopsys.com;
> mcoquelin.stm32@gmail.com; netdev@vger.kernel.org;
> linux-kernel@vger.kernel.org; linux-stm32@st-md-mailman.stormreply.com;
> linux-arm-kernel@lists.infradead.org; dl-linux-imx <linux-imx@nxp.com>
> Subject: Re: [PATCH net 1/2] net: fec_ptp: add clock rate zero check
> 
> On Wed, Jun 16, 2021 at 05:14:25PM +0800, Joakim Zhang wrote:
> > From: Fugang Duan <fugang.duan@nxp.com>
> >
> > Add clock rate zero check to fix coverity issue of "divide by 0".
> >
> > Fixes: commit 85bd1798b24a ("net: fec: fix spin_lock dead lock")
> > Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
> > Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
> > ---
> >  drivers/net/ethernet/freescale/fec_ptp.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/freescale/fec_ptp.c
> > b/drivers/net/ethernet/freescale/fec_ptp.c
> > index 1753807cbf97..7326a0612823 100644
> > --- a/drivers/net/ethernet/freescale/fec_ptp.c
> > +++ b/drivers/net/ethernet/freescale/fec_ptp.c
> > @@ -604,6 +604,10 @@ void fec_ptp_init(struct platform_device *pdev, int
> irq_idx)
> >  	fep->ptp_caps.enable = fec_ptp_enable;
> >
> >  	fep->cycle_speed = clk_get_rate(fep->clk_ptp);
> > +	if (!fep->cycle_speed) {
> > +		fep->cycle_speed = NSEC_PER_SEC;
> > +		dev_err(&fep->pdev->dev, "clk_ptp clock rate is zero\n");
> 
> If this is supposed to be an error message, it doesn't convey that something is
> really wrong to the user. Maybe something like this would be more meaningful
> to the user:
> 
> 	"PTP clock rate should not be zero, using 1GHz instead. PTP
> 	clock may be unreliable.\n"
Make Sense.

> It may be appropriate not to publish PTP support for the interface if we don't
> have a valid clock rate, which is probably the safer approach and would
> probably make the problem more noticable to the end user so it gets fixed.

Do you mean that print an error message then return directly? It seems better.

if (!fep->cycle_speed) {
	dev_err(&fep->pdev->dev, "PTP clock rate should not be zero!\n");
	return;
}

Best Regards,
Joakim Zhang
> --
> RMK's Patch system:
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.ar
> mlinux.org.uk%2Fdeveloper%2Fpatches%2F&amp;data=04%7C01%7Cqiangqin
> g.zhang%40nxp.com%7Cb3c85322e359446e4eee08d930b06701%7C686ea1d3
> bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637594356476903644%7CUnknow
> n%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1ha
> WwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=TH4fZJRu8Ii6w7y05N8CHWoQR
> R9OegsYB7VAwgSpTcU%3D&amp;reserved=0
> FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH net 1/2] net: fec_ptp: add clock rate zero check

[Russell King (Oracle)]

Hi Joakim,

On Wed, Jun 16, 2021 at 11:40:29AM +0000, Joakim Zhang wrote:
> Do you mean that print an error message then return directly? It seems better.

Nearly - one has to ensure that the cleanup functions don't provoke a
crash though. I notice fec_ptp_stop() makes use of fep->time_keep
and also fep->ptp_clock.

fep->time_keep is initialised after where you need to test for zero
cycle_speed, so the initialisation would need moving earlier.

I would have thought that ftp->ptp_clock should be NULL, so that's
probably okay, but should be checked that this assumption is in fact
true.

> if (!fep->cycle_speed) {
> 	dev_err(&fep->pdev->dev, "PTP clock rate should not be zero!\n");

I'd still say something like "PTP clock rate should not be zero,
disabling PTP" - say what's wrong and what we are doing. Also,
please avoid exclaimation marks in error messages.

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

Re: [PATCH net 1/2] net: fec_ptp: add clock rate zero check

[Russell King (Oracle)]

Hi Joakim,

On Wed, Jun 16, 2021 at 11:40:29AM +0000, Joakim Zhang wrote:
> Do you mean that print an error message then return directly? It seems better.

Nearly - one has to ensure that the cleanup functions don't provoke a
crash though. I notice fec_ptp_stop() makes use of fep->time_keep
and also fep->ptp_clock.

fep->time_keep is initialised after where you need to test for zero
cycle_speed, so the initialisation would need moving earlier.

I would have thought that ftp->ptp_clock should be NULL, so that's
probably okay, but should be checked that this assumption is in fact
true.

> if (!fep->cycle_speed) {
> 	dev_err(&fep->pdev->dev, "PTP clock rate should not be zero!\n");

I'd still say something like "PTP clock rate should not be zero,
disabling PTP" - say what's wrong and what we are doing. Also,
please avoid exclaimation marks in error messages.

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH net 2/2] net: fec_ptp: fix issue caused by refactor the fec_devtype

[Joakim Zhang]

Commit da722186f654 ("net: fec: set GPR bit on suspend by DT configuration.")
refactor the fec_devtype, need adjust ptp driver accordingly.

Fixes: da722186f654 ("net: fec: set GPR bit on suspend by DT configuration.")
Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
---
 drivers/net/ethernet/freescale/fec_ptp.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_ptp.c b/drivers/net/ethernet/freescale/fec_ptp.c
index 7326a0612823..d71eac7e1924 100644
--- a/drivers/net/ethernet/freescale/fec_ptp.c
+++ b/drivers/net/ethernet/freescale/fec_ptp.c
@@ -215,15 +215,13 @@ static u64 fec_ptp_read(const struct cyclecounter *cc)
 {
 	struct fec_enet_private *fep =
 		container_of(cc, struct fec_enet_private, cc);
-	const struct platform_device_id *id_entry =
-		platform_get_device_id(fep->pdev);
 	u32 tempval;
 
 	tempval = readl(fep->hwp + FEC_ATIME_CTRL);
 	tempval |= FEC_T_CTRL_CAPTURE;
 	writel(tempval, fep->hwp + FEC_ATIME_CTRL);
 
-	if (id_entry->driver_data & FEC_QUIRK_BUG_CAPTURE)
+	if (fep->quirks & FEC_QUIRK_BUG_CAPTURE)
 		udelay(1);
 
 	return readl(fep->hwp + FEC_ATIME);
-- 
2.17.1

[PATCH net 2/2] net: fec_ptp: fix issue caused by refactor the fec_devtype

[Joakim Zhang]

Commit da722186f654 ("net: fec: set GPR bit on suspend by DT configuration.")
refactor the fec_devtype, need adjust ptp driver accordingly.

Fixes: da722186f654 ("net: fec: set GPR bit on suspend by DT configuration.")
Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
---
 drivers/net/ethernet/freescale/fec_ptp.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec_ptp.c b/drivers/net/ethernet/freescale/fec_ptp.c
index 7326a0612823..d71eac7e1924 100644
--- a/drivers/net/ethernet/freescale/fec_ptp.c
+++ b/drivers/net/ethernet/freescale/fec_ptp.c
@@ -215,15 +215,13 @@ static u64 fec_ptp_read(const struct cyclecounter *cc)
 {
 	struct fec_enet_private *fep =
 		container_of(cc, struct fec_enet_private, cc);
-	const struct platform_device_id *id_entry =
-		platform_get_device_id(fep->pdev);
 	u32 tempval;
 
 	tempval = readl(fep->hwp + FEC_ATIME_CTRL);
 	tempval |= FEC_T_CTRL_CAPTURE;
 	writel(tempval, fep->hwp + FEC_ATIME_CTRL);
 
-	if (id_entry->driver_data & FEC_QUIRK_BUG_CAPTURE)
+	if (fep->quirks & FEC_QUIRK_BUG_CAPTURE)
 		udelay(1);
 
 	return readl(fep->hwp + FEC_ATIME);
-- 
2.17.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH net 0/2] net: fixes for fec ptp

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (refs/heads/master):

On Wed, 16 Jun 2021 17:14:24 +0800 you wrote:
> Small fixes for fec ptp.
> 
> Fugang Duan (1):
>   net: fec_ptp: add clock rate zero check
> 
> Joakim Zhang (1):
>   net: fec_ptp: fix issue caused by refactor the fec_devtype
> 
> [...]

Here is the summary with links:
  - [net,1/2] net: fec_ptp: add clock rate zero check
    https://git.kernel.org/netdev/net/c/cb3cefe3f3f8
  - [net,2/2] net: fec_ptp: fix issue caused by refactor the fec_devtype
    https://git.kernel.org/netdev/net/c/d23765646e71

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH net 0/2] net: fixes for fec ptp

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (refs/heads/master):

On Wed, 16 Jun 2021 17:14:24 +0800 you wrote:
> Small fixes for fec ptp.
> 
> Fugang Duan (1):
>   net: fec_ptp: add clock rate zero check
> 
> Joakim Zhang (1):
>   net: fec_ptp: fix issue caused by refactor the fec_devtype
> 
> [...]

Here is the summary with links:
  - [net,1/2] net: fec_ptp: add clock rate zero check
    https://git.kernel.org/netdev/net/c/cb3cefe3f3f8
  - [net,2/2] net: fec_ptp: fix issue caused by refactor the fec_devtype
    https://git.kernel.org/netdev/net/c/d23765646e71

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html



_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel