[PATCH] net: fec: check DMA addressing limitations

[PATCH] net: fec: check DMA addressing limitations

[Stefan Agner]

Check DMA addressing limitations as suggested by the DMA API
how-to. This does not fix a particular issue seen but is
considered good style.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 drivers/net/ethernet/freescale/fec_main.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index c729665107f5..af0fb200e936 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -3146,6 +3146,12 @@ static int fec_enet_init(struct net_device *ndev)
 	fep->tx_align = 0x3;
 #endif
 
+	/* Check mask of the streaming and coherent API */
+	if (dma_set_mask_and_coherent(&fep->pdev->dev, DMA_BIT_MASK(32))) {
+		dev_warn(&fep->pdev->dev, "No suitable DMA available\n");
+		return -ENODEV;
+	}
+
 	fec_enet_alloc_queue(ndev);
 
 	bd_size = (fep->total_tx_ring_size + fep->total_rx_ring_size) * dsize;
-- 
2.18.0

RE: [PATCH] net: fec: check DMA addressing limitations

[Andy Duan]

From: Stefan Agner <stefan@agner.ch> Sent: 2018年8月1日 19:45
> Check DMA addressing limitations as suggested by the DMA API how-to.
> This does not fix a particular issue seen but is considered good style.
> 
> Signed-off-by: Stefan Agner <stefan@agner.ch>
> ---
>  drivers/net/ethernet/freescale/fec_main.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/net/ethernet/freescale/fec_main.c
> b/drivers/net/ethernet/freescale/fec_main.c
> index c729665107f5..af0fb200e936 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -3146,6 +3146,12 @@ static int fec_enet_init(struct net_device
> *ndev)
>  	fep->tx_align = 0x3;
>  #endif
> 
> +	/* Check mask of the streaming and coherent API */
> +	if (dma_set_mask_and_coherent(&fep->pdev->dev,
> DMA_BIT_MASK(32))) {
> +		dev_warn(&fep->pdev->dev, "No suitable DMA available\n");
> +		return -ENODEV;
It is better:

ret = dma_set_mask_and_coherent(&fep->pdev->dev, DMA_BIT_MASK(32));
if (ret < 0) {
	dev_warn(&fep->pdev->dev, "No suitable DMA available\n");
	return ret;
}


If the patch aim to "OF: Don't set default coherent DMA mask", I think not only this driver need to add the DMA mask limitations,  many other drivers also need.


> +	}
> +
>  	fec_enet_alloc_queue(ndev);
> 
>  	bd_size = (fep->total_tx_ring_size + fep->total_rx_ring_size) * dsize;
> --
> 2.18.0

Re: [PATCH] net: fec: check DMA addressing limitations

[Stefan Agner]

On 02.08.2018 04:00, Andy Duan wrote:
> From: Stefan Agner <stefan@agner.ch> Sent: 2018年8月1日 19:45
>> Check DMA addressing limitations as suggested by the DMA API how-to.
>> This does not fix a particular issue seen but is considered good style.
>>
>> Signed-off-by: Stefan Agner <stefan@agner.ch>
>> ---
>>  drivers/net/ethernet/freescale/fec_main.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/freescale/fec_main.c
>> b/drivers/net/ethernet/freescale/fec_main.c
>> index c729665107f5..af0fb200e936 100644
>> --- a/drivers/net/ethernet/freescale/fec_main.c
>> +++ b/drivers/net/ethernet/freescale/fec_main.c
>> @@ -3146,6 +3146,12 @@ static int fec_enet_init(struct net_device
>> *ndev)
>>  	fep->tx_align = 0x3;
>>  #endif
>>
>> +	/* Check mask of the streaming and coherent API */
>> +	if (dma_set_mask_and_coherent(&fep->pdev->dev,
>> DMA_BIT_MASK(32))) {
>> +		dev_warn(&fep->pdev->dev, "No suitable DMA available\n");
>> +		return -ENODEV;
> It is better:
> 
> ret = dma_set_mask_and_coherent(&fep->pdev->dev, DMA_BIT_MASK(32));
> if (ret < 0) {
> 	dev_warn(&fep->pdev->dev, "No suitable DMA available\n");
> 	return ret;
> }

The code comes from the example in Documentation/DMA-API-HOWTO.txt.

I can rearrange if you prefer.

> 
> 
> If the patch aim to "OF: Don't set default coherent DMA mask", I think
> not only this driver need to add the DMA mask limitations,  many other
> drivers also need.

It doesn't exactly address the issue since with that patch DMA mask
wasn't set at all. This code would just make the driver fail with
-ENODEV instead of -ENOMEM.

To force a DMA mask I would have to set the DMA mask using
dma_coerce_mask_and_coherent(). But as discussed with Robin it is safe
to assume that an initial mask is set by the bus code:
http://lkml.kernel.org/r/892f9d14-e6fd-7b1b-d07b-af0be6e623fa@arm.com

Setting the DMA mask on DT buses has been addressed by Robin with
"of/platform: Initialise default DMA masks". So everything should be
fine again.

I agree, other drivers need fixing too.

--
Stefan

> 
> 
>> +	}
>> +
>>  	fec_enet_alloc_queue(ndev);
>>
>>  	bd_size = (fep->total_tx_ring_size + fep->total_rx_ring_size) * dsize;
>> --
>> 2.18.0

RE: [PATCH] net: fec: check DMA addressing limitations

[Andy Duan]

From: Stefan Agner <stefan@agner.ch> Sent: 2018年8月2日 15:16
> On 02.08.2018 04:00, Andy Duan wrote:
> > From: Stefan Agner <stefan@agner.ch> Sent: 2018年8月1日 19:45
> >> Check DMA addressing limitations as suggested by the DMA API how-to.
> >> This does not fix a particular issue seen but is considered good style.
> >>
> >> Signed-off-by: Stefan Agner <stefan@agner.ch>
> >> ---
> >>  drivers/net/ethernet/freescale/fec_main.c | 6 ++++++
> >>  1 file changed, 6 insertions(+)
> >>
> >> diff --git a/drivers/net/ethernet/freescale/fec_main.c
> >> b/drivers/net/ethernet/freescale/fec_main.c
> >> index c729665107f5..af0fb200e936 100644
> >> --- a/drivers/net/ethernet/freescale/fec_main.c
> >> +++ b/drivers/net/ethernet/freescale/fec_main.c
> >> @@ -3146,6 +3146,12 @@ static int fec_enet_init(struct net_device
> >> *ndev)
> >>  	fep->tx_align = 0x3;
> >>  #endif
> >>
> >> +	/* Check mask of the streaming and coherent API */
> >> +	if (dma_set_mask_and_coherent(&fep->pdev->dev,
> >> DMA_BIT_MASK(32))) {
> >> +		dev_warn(&fep->pdev->dev, "No suitable DMA
> available\n");
> >> +		return -ENODEV;
> > It is better:
> >
> > ret = dma_set_mask_and_coherent(&fep->pdev->dev,
> DMA_BIT_MASK(32)); if
> > (ret < 0) {
> > 	dev_warn(&fep->pdev->dev, "No suitable DMA available\n");
> > 	return ret;
> > }
> 
> The code comes from the example in
> Documentation/DMA-API-HOWTO.txt.
> 
> I can rearrange if you prefer.
> 
It is better to return the real error code like -EIO if dma_mask is not initialized. 

> >
> >
> > If the patch aim to "OF: Don't set default coherent DMA mask", I think
> > not only this driver need to add the DMA mask limitations,  many other
> > drivers also need.
> 
> It doesn't exactly address the issue since with that patch DMA mask wasn't
> set at all. This code would just make the driver fail with -ENODEV instead of
> -ENOMEM.
> 
Yes, I agree. It doesn't address the issue if no patch "of/platform: Initialise default DMA masks".

For non-DT, it seems dma_coerce_mask_and_coherent() much better.

> To force a DMA mask I would have to set the DMA mask using
> dma_coerce_mask_and_coherent(). But as discussed with Robin it is safe
> to assume that an initial mask is set by the bus code:
> https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flk
> ml.kernel.org%2Fr%2F892f9d14-e6fd-7b1b-d07b-af0be6e623fa%40arm.c
> om&amp;data=02%7C01%7Cfugang.duan%40nxp.com%7C618543fb9b4e
> 4f9fa49908d5f847c47f%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%
> 7C0%7C636687909487381876&amp;sdata=hyeeh0KSC3Fu7VDl4A8JbcCO
> %2FwocUpTEMvTv1hjba0E%3D&amp;reserved=0
> 
> Setting the DMA mask on DT buses has been addressed by Robin with
> "of/platform: Initialise default DMA masks". So everything should be fine
> again.
> 
Anyway, I am fine with the patch except the return code.
Thanks.

> I agree, other drivers need fixing too.
> 
> --
> Stefan
> 
> >
> >
> >> +	}
> >> +
> >>  	fec_enet_alloc_queue(ndev);
> >>
> >>  	bd_size = (fep->total_tx_ring_size + fep->total_rx_ring_size) *
> >> dsize;
> >> --
> >> 2.18.0

Re: [PATCH] net: fec: check DMA addressing limitations

[Stefan Agner]

On 02.08.2018 09:47, Andy Duan wrote:
> From: Stefan Agner <stefan@agner.ch> Sent: 2018年8月2日 15:16
>> On 02.08.2018 04:00, Andy Duan wrote:
>> > From: Stefan Agner <stefan@agner.ch> Sent: 2018年8月1日 19:45
>> >> Check DMA addressing limitations as suggested by the DMA API how-to.
>> >> This does not fix a particular issue seen but is considered good style.
>> >>
>> >> Signed-off-by: Stefan Agner <stefan@agner.ch>
>> >> ---
>> >>  drivers/net/ethernet/freescale/fec_main.c | 6 ++++++
>> >>  1 file changed, 6 insertions(+)
>> >>
>> >> diff --git a/drivers/net/ethernet/freescale/fec_main.c
>> >> b/drivers/net/ethernet/freescale/fec_main.c
>> >> index c729665107f5..af0fb200e936 100644
>> >> --- a/drivers/net/ethernet/freescale/fec_main.c
>> >> +++ b/drivers/net/ethernet/freescale/fec_main.c
>> >> @@ -3146,6 +3146,12 @@ static int fec_enet_init(struct net_device
>> >> *ndev)
>> >>  	fep->tx_align = 0x3;
>> >>  #endif
>> >>
>> >> +	/* Check mask of the streaming and coherent API */
>> >> +	if (dma_set_mask_and_coherent(&fep->pdev->dev,
>> >> DMA_BIT_MASK(32))) {
>> >> +		dev_warn(&fep->pdev->dev, "No suitable DMA
>> available\n");
>> >> +		return -ENODEV;
>> > It is better:
>> >
>> > ret = dma_set_mask_and_coherent(&fep->pdev->dev,
>> DMA_BIT_MASK(32)); if
>> > (ret < 0) {
>> > 	dev_warn(&fep->pdev->dev, "No suitable DMA available\n");
>> > 	return ret;
>> > }
>>
>> The code comes from the example in
>> Documentation/DMA-API-HOWTO.txt.
>>
>> I can rearrange if you prefer.
>>
> It is better to return the real error code like -EIO if dma_mask is
> not initialized.

Good point. Will send a v2.

--
Stefan

> 
>> >
>> >
>> > If the patch aim to "OF: Don't set default coherent DMA mask", I think
>> > not only this driver need to add the DMA mask limitations,  many other
>> > drivers also need.
>>
>> It doesn't exactly address the issue since with that patch DMA mask wasn't
>> set at all. This code would just make the driver fail with -ENODEV instead of
>> -ENOMEM.
>>
> Yes, I agree. It doesn't address the issue if no patch "of/platform:
> Initialise default DMA masks".
> 
> For non-DT, it seems dma_coerce_mask_and_coherent() much better.
> 
>> To force a DMA mask I would have to set the DMA mask using
>> dma_coerce_mask_and_coherent(). But as discussed with Robin it is safe
>> to assume that an initial mask is set by the bus code:
>> https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flk
>> ml.kernel.org%2Fr%2F892f9d14-e6fd-7b1b-d07b-af0be6e623fa%40arm.c
>> om&amp;data=02%7C01%7Cfugang.duan%40nxp.com%7C618543fb9b4e
>> 4f9fa49908d5f847c47f%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%
>> 7C0%7C636687909487381876&amp;sdata=hyeeh0KSC3Fu7VDl4A8JbcCO
>> %2FwocUpTEMvTv1hjba0E%3D&amp;reserved=0
>>
>> Setting the DMA mask on DT buses has been addressed by Robin with
>> "of/platform: Initialise default DMA masks". So everything should be fine
>> again.
>>
> Anyway, I am fine with the patch except the return code.
> Thanks.
> 
>> I agree, other drivers need fixing too.
>>
>> --
>> Stefan
>>
>> >
>> >
>> >> +	}
>> >> +
>> >>  	fec_enet_alloc_queue(ndev);
>> >>
>> >>  	bd_size = (fep->total_tx_ring_size + fep->total_rx_ring_size) *
>> >> dsize;
>> >> --
>> >> 2.18.0