linux-kernel - Re: [PATCH v7 2/5] USB: use genalloc for USB HCs with local memory

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Date:   Wed, 29 May 2019 03:38:38 -0700
From:   Greg KH <gregkh@...uxfoundation.org>
To:     laurentiu.tudor@....com
Cc:     hch@....de, stern@...land.harvard.edu, linux-usb@...r.kernel.org,
        marex@...x.de, leoyang.li@....com, linux-kernel@...r.kernel.org,
        robin.murphy@....com, noring@...rew.org, JuergenUrban@....de
Subject: Re: [PATCH v7 2/5] USB: use genalloc for USB HCs with local memory

On Wed, May 29, 2019 at 01:28:40PM +0300, 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. To help users, introduce a new HCD API,
> usb_hcd_setup_local_mem() that will setup up the genalloc backing
> up the device local memory. It will be used in subsequent patches.
> 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.
> For sh arch to compile GENERIC_ALLOCATOR needs to be selected in
> Kconfig.
> 
> For context, see thread here: https://lkml.org/lkml/2019/4/22/357
> 
> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@....com>
> Signed-off-by: Fredrik Noring <noring@...rew.org>
> Tested-by: Fredrik Noring <noring@...rew.org>
> Reported-by: kbuild test robot <lkp@...el.com>
> ---
>  drivers/usb/Kconfig         |  1 +
>  drivers/usb/core/buffer.c   |  9 +++++++++
>  drivers/usb/core/hcd.c      | 36 ++++++++++++++++++++++++++++++++++++
>  drivers/usb/host/ohci-hcd.c | 23 ++++++++++++++++++-----
>  drivers/usb/host/ohci-mem.c | 35 +++++++++++++++++++++++++++++++----
>  drivers/usb/host/ohci.h     |  2 ++
>  include/linux/usb/hcd.h     |  5 +++++
>  7 files changed, 102 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/usb/Kconfig b/drivers/usb/Kconfig
> index e4b27413f528..389c57d8eba7 100644
> --- a/drivers/usb/Kconfig
> +++ b/drivers/usb/Kconfig
> @@ -45,6 +45,7 @@ config USB_ARCH_HAS_HCD
>  config USB
>  	tristate "Support for Host-side USB"
>  	depends on USB_ARCH_HAS_HCD
> +	select GENERIC_ALLOCATOR

Are there any arches that does not have GENERIC_ALLOCATOR?  I don't want
to suddenly cut off a bunch of working systems from having USB support.

thanks,

greg k-h