diff mbox series

[04/12] bcm2835-dma: Advertise the full DMA range

Message ID a56a6d24066a64598efe4343090e51e2223475b8.1706948717.git.andrea.porta@suse.com (mailing list archive)
State New, archived
Headers show
Series Add support for BCM2712 DMA engine | expand

Commit Message

Andrea della Porta Feb. 4, 2024, 6:59 a.m. UTC 
From: Phil Elwell <phil@raspberrypi.com>

Unless the DMA mask is set wider than 32 bits, DMA mapping will use a
bounce buffer.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
 drivers/dma/bcm2835-dma.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

Comments

Robin Murphy Feb. 5, 2024, 5:55 p.m. UTC | #1 
On 2024-02-04 6:59 am, Andrea della Porta wrote:
> From: Phil Elwell <phil@raspberrypi.com>
> 
> Unless the DMA mask is set wider than 32 bits, DMA mapping will use a
> bounce buffer.
> 
> Signed-off-by: Phil Elwell <phil@raspberrypi.com>
> ---
>   drivers/dma/bcm2835-dma.c | 18 +++++++++++++++---
>   1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
> index 36bad198b655..237dcdb8d726 100644
> --- a/drivers/dma/bcm2835-dma.c
> +++ b/drivers/dma/bcm2835-dma.c
> @@ -39,6 +39,7 @@
>   #define BCM2711_DMA_MEMCPY_CHAN 14
>   
>   struct bcm2835_dma_cfg_data {
> +	u64	dma_mask;
>   	u32	chan_40bit_mask;
>   };
>   
> @@ -308,10 +309,12 @@ DEFINE_SPINLOCK(memcpy_lock);
>   
>   static const struct bcm2835_dma_cfg_data bcm2835_dma_cfg = {
>   	.chan_40bit_mask = 0,
> +	.dma_mask = DMA_BIT_MASK(32),
>   };
>   
>   static const struct bcm2835_dma_cfg_data bcm2711_dma_cfg = {
>   	.chan_40bit_mask = BIT(11) | BIT(12) | BIT(13) | BIT(14),
> +	.dma_mask = DMA_BIT_MASK(36),
>   };
>   
>   static inline size_t bcm2835_dma_max_frame_length(struct bcm2835_chan *c)
> @@ -1263,6 +1266,8 @@ static struct dma_chan *bcm2835_dma_xlate(struct of_phandle_args *spec,
>   
>   static int bcm2835_dma_probe(struct platform_device *pdev)
>   {
> +	const struct bcm2835_dma_cfg_data *cfg_data;
> +	const struct of_device_id *of_id;
>   	struct bcm2835_dmadev *od;
>   	struct resource *res;
>   	void __iomem *base;
> @@ -1272,13 +1277,20 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
>   	int irq_flags;
>   	uint32_t chans_available;
>   	char chan_name[BCM2835_DMA_CHAN_NAME_SIZE];
> -	const struct of_device_id *of_id;
>   	int chan_count, chan_start, chan_end;
>   
> +	of_id = of_match_node(bcm2835_dma_of_match, pdev->dev.of_node);
> +	if (!of_id) {
> +		dev_err(&pdev->dev, "Failed to match compatible string\n");
> +		return -EINVAL;
> +	}
> +
> +	cfg_data = of_id->data;

We've had of_device_get_match_data() for nearly 9 years now, and even a 
generic device_get_match_data() for 6 ;)

> +
>   	if (!pdev->dev.dma_mask)
>   		pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask;

[ Passing nit: that also really shouldn't be there, especially since 
cdfee5623290 ]

>   
> -	rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
> +	rc = dma_set_mask_and_coherent(&pdev->dev, cfg_data->dma_mask);

Wait, does chan_40bit_mask mean that you still have some channels which 
*can't* address this full mask? If so this can't work properly. You may 
well need to redesign a bit further to have a separate DMA device for 
each channel such they can each have different masks.

Thanks,
Robin.

>   	if (rc) {
>   		dev_err(&pdev->dev, "Unable to set DMA mask\n");
>   		return rc;
> @@ -1342,7 +1354,7 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
>   		return -EINVAL;
>   	}
>   
> -	od->cfg_data = of_id->data;
> +	od->cfg_data = cfg_data;
>   
>   	/* Request DMA channel mask from device tree */
>   	if (of_property_read_u32(pdev->dev.of_node,
Stefan Wahren Feb. 5, 2024, 6:25 p.m. UTC | #2 
Hi Andrea,

Am 04.02.24 um 07:59 schrieb Andrea della Porta:
> From: Phil Elwell <phil@raspberrypi.com>
>
> Unless the DMA mask is set wider than 32 bits, DMA mapping will use a
> bounce buffer.
>
> Signed-off-by: Phil Elwell <phil@raspberrypi.com>
this lacks your Signed-off-by

Regards
Andrea della Porta March 1, 2024, 1:55 p.m. UTC | #3 
On 17:55 Mon 05 Feb     , Robin Murphy wrote:
> On 2024-02-04 6:59 am, Andrea della Porta wrote:
> > From: Phil Elwell <phil@raspberrypi.com>
> > 
> > Unless the DMA mask is set wider than 32 bits, DMA mapping will use a
> > bounce buffer.
> > 
> > Signed-off-by: Phil Elwell <phil@raspberrypi.com>
> > ---
> >   drivers/dma/bcm2835-dma.c | 18 +++++++++++++++---
> >   1 file changed, 15 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
> > index 36bad198b655..237dcdb8d726 100644
> > --- a/drivers/dma/bcm2835-dma.c
> > +++ b/drivers/dma/bcm2835-dma.c
> > @@ -39,6 +39,7 @@
> >   #define BCM2711_DMA_MEMCPY_CHAN 14
> >   struct bcm2835_dma_cfg_data {
> > +	u64	dma_mask;
> >   	u32	chan_40bit_mask;
> >   };
> > @@ -308,10 +309,12 @@ DEFINE_SPINLOCK(memcpy_lock);
> >   static const struct bcm2835_dma_cfg_data bcm2835_dma_cfg = {
> >   	.chan_40bit_mask = 0,
> > +	.dma_mask = DMA_BIT_MASK(32),
> >   };
> >   static const struct bcm2835_dma_cfg_data bcm2711_dma_cfg = {
> >   	.chan_40bit_mask = BIT(11) | BIT(12) | BIT(13) | BIT(14),
> > +	.dma_mask = DMA_BIT_MASK(36),
> >   };
> >   static inline size_t bcm2835_dma_max_frame_length(struct bcm2835_chan *c)
> > @@ -1263,6 +1266,8 @@ static struct dma_chan *bcm2835_dma_xlate(struct of_phandle_args *spec,
> >   static int bcm2835_dma_probe(struct platform_device *pdev)
> >   {
> > +	const struct bcm2835_dma_cfg_data *cfg_data;
> > +	const struct of_device_id *of_id;
> >   	struct bcm2835_dmadev *od;
> >   	struct resource *res;
> >   	void __iomem *base;
> > @@ -1272,13 +1277,20 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
> >   	int irq_flags;
> >   	uint32_t chans_available;
> >   	char chan_name[BCM2835_DMA_CHAN_NAME_SIZE];
> > -	const struct of_device_id *of_id;
> >   	int chan_count, chan_start, chan_end;
> > +	of_id = of_match_node(bcm2835_dma_of_match, pdev->dev.of_node);
> > +	if (!of_id) {
> > +		dev_err(&pdev->dev, "Failed to match compatible string\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	cfg_data = of_id->data;
> 
> We've had of_device_get_match_data() for nearly 9 years now, and even a
> generic device_get_match_data() for 6 ;)
> 
> > +
> >   	if (!pdev->dev.dma_mask)
> >   		pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask;
> 
> [ Passing nit: that also really shouldn't be there, especially since
> cdfee5623290 ]
> 
> > -	rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
> > +	rc = dma_set_mask_and_coherent(&pdev->dev, cfg_data->dma_mask);
> 
> Wait, does chan_40bit_mask mean that you still have some channels which
> *can't* address this full mask? If so this can't work properly. You may well
> need to redesign a bit further to have a separate DMA device for each
> channel such they can each have different masks.
>

It seems that the original intention here was to create a device for each value of dma_mask in
hw descriptors. That is, for 2711 which has 32 and 40 bit channels, the DT should look something
like this:

	dma: dma-controller@7e007000 {
		interrupts = <...>;
		brcm,dma-channel-mask = <0x7f5>;
		compatible = "brcm,bcm2835-dma";
		interrupt-names = "...";
		reg = <0x7e007000 0xb00>;
		#dma-cells = <0x01>;
	};      

	dma40: dma-controller@7e007b00 {
		interrupts = <...>;     
		brcm,dma-channel-mask = <0x3000>;
		compatible = "brcm,bcm2711-dma";
		interrupt-names = "...";
		reg = <0x00 0x7e007b00 0x00 0x400>;
		#dma-cells = <0x01>;
	};

Two devices dma0 and dma1 will be created, each one serving a different mask and the call
to dma_set_mask_and_coherent(..., dma_mask) on the specific device will be consistent. Please
note that of course "brcm,dma-channel-mask" from DT only refers to what channels are available
to be used in the kernel, while dma_mask parameter of the aforementioned dma_set_mask_and_coherent()
call is the addressing mask enforced by the driver, and its the same for each specific device
(dma0 or dma1).

Many thanks,
Andrea
diff mbox series

Patch

diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
index 36bad198b655..237dcdb8d726 100644
--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -39,6 +39,7 @@ 
 #define BCM2711_DMA_MEMCPY_CHAN 14
 
 struct bcm2835_dma_cfg_data {
+	u64	dma_mask;
 	u32	chan_40bit_mask;
 };
 
@@ -308,10 +309,12 @@  DEFINE_SPINLOCK(memcpy_lock);
 
 static const struct bcm2835_dma_cfg_data bcm2835_dma_cfg = {
 	.chan_40bit_mask = 0,
+	.dma_mask = DMA_BIT_MASK(32),
 };
 
 static const struct bcm2835_dma_cfg_data bcm2711_dma_cfg = {
 	.chan_40bit_mask = BIT(11) | BIT(12) | BIT(13) | BIT(14),
+	.dma_mask = DMA_BIT_MASK(36),
 };
 
 static inline size_t bcm2835_dma_max_frame_length(struct bcm2835_chan *c)
@@ -1263,6 +1266,8 @@  static struct dma_chan *bcm2835_dma_xlate(struct of_phandle_args *spec,
 
 static int bcm2835_dma_probe(struct platform_device *pdev)
 {
+	const struct bcm2835_dma_cfg_data *cfg_data;
+	const struct of_device_id *of_id;
 	struct bcm2835_dmadev *od;
 	struct resource *res;
 	void __iomem *base;
@@ -1272,13 +1277,20 @@  static int bcm2835_dma_probe(struct platform_device *pdev)
 	int irq_flags;
 	uint32_t chans_available;
 	char chan_name[BCM2835_DMA_CHAN_NAME_SIZE];
-	const struct of_device_id *of_id;
 	int chan_count, chan_start, chan_end;
 
+	of_id = of_match_node(bcm2835_dma_of_match, pdev->dev.of_node);
+	if (!of_id) {
+		dev_err(&pdev->dev, "Failed to match compatible string\n");
+		return -EINVAL;
+	}
+
+	cfg_data = of_id->data;
+
 	if (!pdev->dev.dma_mask)
 		pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask;
 
-	rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
+	rc = dma_set_mask_and_coherent(&pdev->dev, cfg_data->dma_mask);
 	if (rc) {
 		dev_err(&pdev->dev, "Unable to set DMA mask\n");
 		return rc;
@@ -1342,7 +1354,7 @@  static int bcm2835_dma_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
-	od->cfg_data = of_id->data;
+	od->cfg_data = cfg_data;
 
 	/* Request DMA channel mask from device tree */
 	if (of_property_read_u32(pdev->dev.of_node,