Re: ensure dma_alloc_coherent always returns zeroed memory

[Eugeniy Paltsev]

Hi Christoph,

I test kernel from your 'dma-alloc-always-zero' branch, and as
I can see we have DMA peripherals (like USB) broken.

There are the errors example I got during USB initializing:
------------------------------>8--------------------------------
usb 1-1: device descriptor read/64, error -110
usb usb1-port1: attempt power cycle
usb 1-1: new high-speed USB device number 4 using ehci-platform
usb 1-1: device descriptor read/64, error -110
usb 1-1: device descriptor read/64, error -110
usb 1-1: new high-speed USB device number 5 using ehci-platform
usb 1-1: device descriptor read/64, error -110
usb 1-1: device descriptor read/64, error -110
usb usb1-port1: unable to enumerate USB device
usb 2-1: new full-speed USB device number 2 using ohci-platform
usb 2-1: device descriptor read/all, error -84
usb 2-1: new full-speed USB device number 3 using ohci-platform
usb 2-1: device descriptor read/all, error -84
usb usb2-port1: attempt power cycle
usb 2-1: new full-speed USB device number 4 using ohci-platform
usb 2-1: device descriptor read/8, error -62
usb 2-1: device descriptor read/8, error -62
usb 2-1: new full-speed USB device number 5 using ohci-platform
usb 2-1: device descriptor read/8, error -84
usb 2-1: device descriptor read/8, error -84
usb usb2-port1: unable to enumerate USB device
 [snip]
------------------------------8<--------------------------------


On Wed, 2018-12-19 at 17:59 +0100, Christoph Hellwig wrote:
> FYI, I've picked this up for dma-mapping for-next now.
> 
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-- 
 Eugeniy Paltsev