Messages in this thread | | | Date | Tue, 14 May 2019 08:11:41 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH] nvme/pci: Use host managed power state for suspend |
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On Mon, May 13, 2019 at 06:01:39PM +0000, Mario.Limonciello@dell.com wrote: > When using HMB the SSD will be writing to some memory mapped region. > Writing to > that region would use DMA to access host memory, no?
Memory mapped region? It will use the devices DMA engine to write host memory, which we explicitly allowed it.
> If the DMA controller is not functional writing to that region won't work properly as > it can't access that memory.
The DMA controller is in the device. External DMA controllers are only used on very low-end periphals, usually cheap IP blocks like SPI controllers or similar.
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