On 13.01.2016 14:43, Vinod Koul wrote:
On Wed, Jan 13, 2016 at 02:30:32PM +0100, Martin Sperl wrote:
On 13.01.2016 13:26, Vinod Koul wrote:
On Thu, Jan 07, 2016 at 05:33:01PM +0000, kernel@xxxxxxxxxxxxxxxx wrote:
@@ -638,13 +666,21 @@ static int bcm2835_dma_probe(struct platform_device *pdev)
goto err_no_dma;
}
- for (i = 0; i < pdev->num_resources; i++) {
- irq = platform_get_irq(pdev, i);
+ for (i = 0; i <= BCM2835_DMA_MAX_CHANNEL_NUMBER; i++) {
+ if (BCM2835_DMA_IRQ_SHARED_MASK & BIT(i)) {
Ideally this should be done thru DT data and not hard coded in kernel. I
dont think this assumption will hold good for next gen of this device, so
better to get this from DT!
The ideal solution would be breaking the DT in such a way that we could
define a register range and interrupt per dma-channel looking something
like this:
diff --git a/arch/arm/boot/dts/bcm2835.dtsi b/arch/arm/boot/dts/bcm2835.dtsi
index 83d9787..9526b91 100644
--- a/arch/arm/boot/dts/bcm2835.dtsi
+++ b/arch/arm/boot/dts/bcm2835.dtsi
@@ -31,8 +31,28 @@
dma: dma@7e007000 {
compatible = "brcm,bcm2835-dma";
- reg = <0x7e007000 0xf00>;
- interrupts = <1 16>,
+ reg = <0x7e007f00 0x100>, /* status reg */
+ <0x7e007000 0x100>,
+ <0x7e007100 0x100>,
+ <0x7e007200 0x100>,
+ <0x7e007300 0x100>,
+ <0x7e007400 0x100>,
+ <0x7e007500 0x100>,
+ <0x7e007600 0x100>,
+ <0x7e007700 0x100>,
+ <0x7e007800 0x100>,
+ <0x7e007900 0x100>,
+ <0x7e007a00 0x100>,
+ <0x7e007b00 0x100>,
+ <0x7e007c00 0x100>,
+ <0x7e007d00 0x100>,
+ <0x7e007e00 0x100>,
+ /* dma channel 15 uses a different base */
+ <0x7ee05000 0x100>;
+ interrupts = <1 28>, /* catch all DMA-interrupts */
+ /* dma channel 0-10 interrupts */
+ <1 16>,
<1 17>,
<1 18>,
<1 19>,
@@ -43,9 +63,30 @@
<1 24>,
<1 25>,
<1 26>,
+ /* dma channel 11-14 share irq */
<1 27>,
- <1 28>;
-
+ <1 27>,
+ <1 27>,
+ <1 27>,
+ /* no irq support for dma channel 15 */
+ < 0 >;
+ dma-names = "shared",
+ "dma0",
+ "dma1",
+ "dma2",
+ "dma3",
+ "dma4",
+ "dma5",
+ "dma6",
+ "dma7",
+ "dma8",
+ "dma9",
+ "dma10",
+ "dma11",
+ "dma12",
+ "dma13",
+ "dma14",
+ "dma15";
#dma-cells = <1>;
brcm,dma-channel-mask = <0x7f35>;
(or similar)
This actually would allow us to make "brcm,dma-channel-mask" redundant,
as we could remove those dma channels that are owned by the firmware
directly from the list.
That way we could also map other capabilities via the DT.
It would also allow a transparent addition of additional dma channels
with newer versions of the HW - mostly - by modifying the DT.
Precisely
But that would be frowned upon, so I had to come up with the approach
taken, which makes the following assumptions:
DT was designed to move this info and hardcoding from kernel into
DT, so why cant we do that?
We still need to be backwards-compatible - at least that is what
everyone tells me, so I need to hard-code fallbacks for those values.
* the DT maps only the interrupts that are assigned to the HW block
* the driver knows about the number of DMA channels in HW
that could be a DT property, yes.
* the driver knows about the mapping of shared interrupts
(11-14 share irq).
OK - how would you define that "mapping" in a "sane" manner in the DT
that allows us to have multiple such mappings in the future?
It is not optimal, but at least it works with the least amount of
change to the DT - and what about all those assumptions that we
would need to hard-code to be backwards compatible to the DT without?
I guess we could replace BCM2835_DMA_MAX_CHANNEL_NUMBER with:
/* we do not support dma channel 15 with this driver */
#define BCM2835_DMA_MAX_CHANNEL_SUPPORTED 14
...
for (i = 0;
i <= min_t(int, flv(chans_available),
BCM2835_DMA_MAX_CHANNEL_SUPPORTED);
i++) {
So which way would you prefer this to go - I got another few days
before I leave on vacation.
I still think DT is the right way to go here, unless I hear some other
convincing answer..
The point is that the way the DT is right now it becomes very hard to
extend it in a sane manner - It would be bitmaps/lists here,
bitmaps/lists there...
Breaking the DT would make all of it go away.
If I think of it (reading your other comments), then here how the
"new" DT could look like:
dma: dma@7e007f00 {
/* new compatible name to map to new driver */
compatible = "brcm,bcm2835-dma-v2";
/* the status/enable registers */
reg = <0x7e007f00 0x100>;
/* the catch all interrupt */
interrupts = <1 28>;
dma0: dma-channel@0x7e007000 {
reg = <0x7e007000 0x100>;
interrupts = <1 16>;
};
...
dma7: dma-channel@0x7e007700 {
reg = <0x7e007700 0x100>;
interrupts = <1 23>;
dma-channel-type = <BCM2835_DMA_LITE>;
dma-max-length = <65532>; /* 64K - 4 */
};
...
dma11: dma-channel@0x7e007b00 {
reg = <0x7e007b00 0x100>;
interrupts = <1 27>;
shared-interrupt;
dma-channel-type = <BCM2835_DMA_LITE>;
};
...
dma14: dma-channel@0x7e007e00 {
reg = <0x7e007e00 0x100>;
interrupts = <1 27>;
shared-interrupt;
dma-channel-type = <BCM2835_DMA_LITE>;
};
dma15: dma-channel@0x7ee05000 {
reg = <0x7ee05000 0x100>;
};
};
Adding additional "features" would make it easy like:
* dma-channel priority on AXI bus
* setting warn/alert levels for DREQs
* eventually mapping of drivers to the explicit dma channel
e.g: SPI has a limit of 65534 bytes per dma transfer in HW,
so the use of a DMA-LITE engine would be sufficient - no need
to waste a "normal" DMA-engine with 2D support,...
So the spi dt node could then look like this:
dmas = <&dma11 BCM2835_DREQ_SPI_TX>, <&dma12 BCM2835_DREQ_SPI_RX>;
dma-names = "tx", "rx";
Is this the approach I should try to take?
Or do you want me to continue on the "patchwork" route:
dma: dma@7e007000 {
interrupt-names = "dma0", ..., "dma10", "shared", "catch-all";
bcrm,dma-lite-channel-mask = <0x7f80>;
bcrm,dma-max-channels = 14;
bcrm,catch-all-interrupt-name = "catch-all";
bcrm,shared-interrupt-name = "shared";
bcrm,shared-interrupt-channel-mapping = <0x7800>;
}
For all of the above we would need to define defaults in the driver
to make it work in a backwards compatible way.
That would not support the registers for each dma channel and not lend
itself towards extending only via the DT - say support DMA channel 15.
I have another 5 days before I leave on vacation - there is only so
much I can do...
Thanks,
Martin
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