RE: [PATCH v28 2/4] dt-bindings: i2c: ast2600-i2c.yaml: Add global-regs and enable-dma properties

Ryan Chen <[email protected]>
Newsgroups org.ozlabs.lists.openbmc,org.infradead.lists.linux-arm-kernel,org.kernel.vger.linux-devicetree,org.kernel.vger.linux-i2c,org.kernel.vger.linux-kernel,org.ozlabs.lists.linux-aspeed
Message-ID <TY2PPF5CB9A1BE6EA5BABE55EB8A7003D22F253A@TY2PPF5CB9A1BE6.apcprd06.prod.outlook.com> 
> Subject: Re: [PATCH v28 2/4] dt-bindings: i2c: ast2600-i2c.yaml: Add global-regs
> and enable-dma properties
> 
> Hi Ryan,
> 
> > All AST2600 I2C controller instances have DMA hardware.
> > I will remove the aspeed,enable-dma property and instead expose sysfs
> > attribute in driver to allow users to enable dma/buffer/byte.
> 
> Sounds reasonable, but before you do so, how are you planning to manage the
> allocation of DMA channels across multiple i2c peripherals?
> 
The AST2600 I2C hardware has only one can use DMA at a time.
To avoid the complexity of managing DMA channel contention,
I plan to use buffer mode by default for all controllers, which still provides
better performance than byte mode without requiring DMA channel allocation.
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