From: Alan Stern <stern@rowland.harvard.edu>
To: Noam Liron <lnoam@marvell.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
Yuval Shaia <yshaia@marvell.com>
Subject: Re: [EXT] Re: Enforce USB DMA allocations to specific range
Date: Thu, 11 Feb 2021 11:00:47 -0500 [thread overview]
Message-ID: <20210211160047.GB822348@rowland.harvard.edu> (raw)
In-Reply-To: <BYAPR18MB2741B58F5907F65C71ACF966B98C9@BYAPR18MB2741.namprd18.prod.outlook.com>
On Thu, Feb 11, 2021 at 08:38:40AM +0000, Noam Liron wrote:
> Hi Greg,
>
> I am writing you again on the below subject, as I would like to get a "high level" opinion, and you are probably the most experienced ...
>
> As I wrote below, I cannot rely on the DMA mask, as some USB allocation are not affected by it.
> I thought of using private DMA pool that will be allocated where I need it (at the start of physical memory). However, this means adding specific ASIC code, which is less elegant.
> Do you think that's the right way?
>
> Thanks,
> Noam
>
>
> -----Original Message-----
> From: Greg KH <greg@kroah.com>
> Sent: Monday, December 28, 2020 4:19 PM
> To: Noam Liron <lnoam@marvell.com>
> Cc: linux-usb@vger.kernel.org; Yuval Shaia <yshaia@marvell.com>
> Subject: [EXT] Re: Enforce USB DMA allocations to specific range
>
> External Email
>
> ----------------------------------------------------------------------
> On Mon, Dec 28, 2020 at 01:54:41PM +0000, Noam Liron wrote:
> > Hi Greg and thanks for your reply for my previous q. (Proper way to set a DMA_MASK on a USB device).
> >
> > I am rephrasing my questions:
> >
> > I am working on LK 4.14.76, on a SOC in which RAM starts at 0x200000000, and need to limit DMA buffer allocations to be at the range 0x200000000 - 0x220000000.
> > This is a SoC constraint.
> > Setting the controller dma_mask to 0x21FFFFFFF, didn't solve the problem, as I noticed that URB streaming DMA are first allocated by kmalloc and alike, which are not affected by the dma_mask.
>
> Why not get support from who ever is forcing you to use that old kernel version? You are paying them for this, right? :)
>
> > I plan to do the following:
> > Alloc coherent memory for the HCD using 'dma_declare_coherent_memory', and use the HCD_LOCAL_MEM so the usb core is told that it must copy data into local memory if the buffers happen to be placed in regular memory.
> >
> > Is that the right way to deal with this case?
I think that is the correct way. That's what the HCD_LOCAL_MEM flag was
meant for.
Alan Stern
> Have you looked at how all of the existing host controller drivers do this? Why will they not "just work" properly for you as well?
> What host controller driver are you using?
>
> thanks,
>
> greg k-h
prev parent reply other threads:[~2021-02-11 16:09 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-28 13:54 Enforce USB DMA allocations to specific range Noam Liron
2020-12-28 14:18 ` Greg KH
2020-12-28 15:18 ` [EXT] " Noam Liron
2021-02-11 8:38 ` Noam Liron
2021-02-11 9:02 ` Greg Kroah-Hartman
2021-02-11 16:00 ` Alan Stern [this message]
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