2020-09-14 05:25:10

by Valmiki

Subject: dma-coherent property for PCIe Root

Hi All,

How does "dma-coherent" property will work for PCIe as RC on an
ARM SOC ?
Because the end point device drivers are the one which will request dma
buffers and Root port driver doesn't involve in data path of end point
except for handling interrupts.

How does EP DMA buffers will be hardware coherent if RC driver exposes
dma-coherent property ?

Regards,
Valmiki

2020-10-01 05:18:49

by Jon Masters

Subject: Re: dma-coherent property for PCIe Root

On 9/14/20 1:23 AM, Valmiki wrote:
> Hi All,
>
> How does "dma-coherent" property will work for PCIe as RC on an
> ARM SOC ?
> Because the end point device drivers are the one which will request dma
> buffers and Root port driver doesn't involve in data path of end point
> except for handling interrupts.
>
> How does EP DMA buffers will be hardware coherent if RC driver exposes
> dma-coherent property ?

This simply means that the RC supports maintaining coherency, it doesn't
mean that the RC driver does anything. It's a property of the hardware.

Jon.

--
Computer Architect