linux-kernel - Re: [RFC PATCH v2 0/3] prerequisites for device reserved local mem rework

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Date:   Tue, 14 May 2019 16:17:35 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     laurentiu.tudor@....com, hch@....de, stern@...land.harvard.edu,
        gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        marex@...x.de, noring@...rew.org, JuergenUrban@....de
Cc:     leoyang.li@....com, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 0/3] prerequisites for device reserved local mem
 rework

+Fredrik, Juergen

On 14/05/2019 15:38, laurentiu.tudor@....com wrote:
> From: Laurentiu Tudor <laurentiu.tudor@....com>
> 
> For HCs that have local memory, replace the current DMA API usage
> with a genalloc generic allocator to manage the mappings for these
> devices.
> This is in preparation for dropping the existing "coherent" dma
> mem declaration APIs. Current implementation was relying on a short
> circuit in the DMA API that in the end, was acting as an allocator
> for these type of devices.
> 
> Only compiled tested, so any volunteers willing to test are most welcome.

I recall an out-of-tree PlayStation 2 OHCI driver being another 
HCD_LOCAL_MEM user - if Fredrik and Juergen are still active on that, 
hopefully they might be able to comment on whether this approach can 
work for them too. Patchwork link just in case: 
https://patchwork.kernel.org/project/linux-usb/list/?series=117433

Robin.

> 
> Thank you!
> 
> For context, see thread here: https://lkml.org/lkml/2019/4/22/357
> 
> Changes in v2:
>   - use genalloc also in core usb (based on comment from Robin)
>   - moved genpool decl to usb_hcd to be accesible from core usb
> 
> Laurentiu Tudor (3):
>    USB: use genalloc for USB HCs with local memory
>    usb: host: ohci-sm501: init genalloc for local memory
>    usb: host: ohci-tmio: init genalloc for local memory
> 
>   drivers/usb/core/buffer.c     | 12 ++++++-
>   drivers/usb/host/ohci-hcd.c   | 23 +++++++++++---
>   drivers/usb/host/ohci-sm501.c | 60 +++++++++++++++++++----------------
>   drivers/usb/host/ohci-tmio.c  | 23 +++++++++-----
>   include/linux/usb/hcd.h       |  3 ++
>   5 files changed, 80 insertions(+), 41 deletions(-)
>