[PATCH V2 3/8] dmaengine: bcm2835: use shared interrupt for channel 11 to 14.
From: Martin Sperl <hidden>
Date: 2016-01-13 13:30:32
Subsystem:
the rest · Maintainer:
Linus Torvalds
On 13.01.2016 13:26, Vinod Koul wrote:
On Thu, Jan 07, 2016 at 05:33:01PM +0000, kernel at martin.sperl.org wrote:quoted
@@ -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 at 7e007000 { compatible = "brcm,bcm2835-dma"; - reg = <0x7e007000 0xf00>; - interrupts = <1 16>, + reg = <0x7e007f00 0x100>, /* status reg */ + /* dma channel 0-14 base addresses */ + <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.
But that would be frowned upon, so I had to come up with the approach
taken, which makes the following assumptions:
* the DT maps only the interrupts that are assigned to the HW block
* the driver knows about the number of DMA channels in HW
* the driver knows about the mapping of shared interrupts
(11-14 share irq).
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.
Thanks,
Martin