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SubjectRe: [PATCH 02/14] dmaengine: dma-jz4780: Separate chan/ctrl registers


Le lun. 9 juil. 2018 à 19:03, Vinod <vkoul@kernel.org> a écrit :
> On 03-07-18, 14:32, Paul Cercueil wrote:
>> The register area of the JZ4780 DMA core can be split into different
>> sections for different purposes:
>>
>> * one set of registers is used to perform actions at the DMA core
>> level,
>> that will generally affect all channels;
>>
>> * one set of registers per DMA channel, to perform actions at the
>> DMA
>> channel level, that will only affect the channel in question.
>>
>> The problem rises when trying to support new versions of the JZ47xx
>> Ingenic SoC. For instance, the JZ4770 has two DMA cores, each one
>> with six DMA channels, and the register sets are interleaved:
>> <DMA0 chan regs> <DMA1 chan regs> <DMA0 ctrl regs> <DMA1 ctrl regs>
>>
>> By using one memory resource for the channel-specific registers and
>> one memory resource for the core-specific registers, we can support
>> the JZ4770, by initializing the driver once per DMA core with
>> different
>> addresses.
>>
>> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
>> ---
>> .../devicetree/bindings/dma/jz4780-dma.txt | 6 +-
>
> Pls move to separate patch.

OK.

>> drivers/dma/dma-jz4780.c | 106
>> +++++++++++-------
>> 2 files changed, 69 insertions(+), 43 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/dma/jz4780-dma.txt
>> b/Documentation/devicetree/bindings/dma/jz4780-dma.txt
>> index f25feee62b15..f9b1864f5b77 100644
>> --- a/Documentation/devicetree/bindings/dma/jz4780-dma.txt
>> +++ b/Documentation/devicetree/bindings/dma/jz4780-dma.txt
>> @@ -3,7 +3,8 @@
>> Required properties:
>>
>> - compatible: Should be "ingenic,jz4780-dma"
>> -- reg: Should contain the DMA controller registers location and
>> length.
>> +- reg: Should contain the DMA channel registers location and
>> length, followed
>> + by the DMA controller registers location and length.
>> - interrupts: Should contain the interrupt specifier of the DMA
>> controller.
>> - interrupt-parent: Should be the phandle of the interrupt
>> controller that
>> - clocks: Should contain a clock specifier for the JZ4780 PDMA
>> clock.
>> @@ -22,7 +23,8 @@ Example:
>>
>> dma: dma@13420000 {
>> compatible = "ingenic,jz4780-dma";
>> - reg = <0x13420000 0x10000>;
>> + reg = <0x13420000 0x400
>> + 0x13421000 0x40>;
>
> Second should be optional or we break platform which may not have
> updated DT..

See comment below.

>> - jzdma->base = devm_ioremap_resource(dev, res);
>> - if (IS_ERR(jzdma->base))
>> - return PTR_ERR(jzdma->base);
>> + jzdma->chn_base = devm_ioremap_resource(dev, res);
>> + if (IS_ERR(jzdma->chn_base))
>> + return PTR_ERR(jzdma->chn_base);
>> +
>> + res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
>> + if (!res) {
>> + dev_err(dev, "failed to get I/O memory\n");
>> + return -EINVAL;
>> + }
>
> okay and this breaks if you happen to get probed on older DT. I think
> DT
> is treated as ABI so you need to continue support older method while
> finding if DT has split resources

See my response to PrasannaKumar. All the Ingenic-based boards do
compile
the devicetree within the kernel, so I think it's still fine to add
breaking
changes. I'll wait on @Rob to give his point of view on this, though.

(It's not something hard to change, but I'd like to know what's the
policy
in that case. I have other DT-breaking patches to submit)

> --
> ~Vinod

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