From: Christoph Hellwig <hch@infradead.org>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Alan Stern <stern@rowland.harvard.edu>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] USB: OHCI: ohci-sm501: complete URBs in BH context
Date: Mon, 6 Aug 2018 01:37:30 -0700 [thread overview]
Message-ID: <20180806083730.GA32650@infradead.org> (raw)
In-Reply-To: <1533355279-26725-1-git-send-email-linux@roeck-us.net>
On Fri, Aug 03, 2018 at 09:01:19PM -0700, Guenter Roeck wrote:
> Testing an USB drive connected to ohci-sm501 results in a large number
> of runtime warnings.
As far as I can tell this driver uses the HCD_LOCAL_MEM feature flag
for memory declared using dma_declare_coherent_memory. Unlike the
mormal dma mapping interfaces this special case can actually be freed
from interrupt context, and we have a fix for this warning queued
up in linux-next:
http://git.infradead.org/users/hch/dma-mapping.git/commitdiff/d27fb99f62af7b79c542d161aa5155ed57271ddc
That being said I'm generally very unhappy how dma_init_coherent_memory
turned out. The idea was to allow device local memory to be hidden
behind the DMA API, but in general we use it either as a way to declare
special uncache system memory (which would really be the plaform codes
job), or as a magic bounce buffer like in the USB code. I plan to
eventually untangle this, but it is going to take some time.
next prev parent reply other threads:[~2018-08-06 8:37 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-04 4:01 [PATCH] USB: OHCI: ohci-sm501: complete URBs in BH context Guenter Roeck
2018-08-04 14:50 ` Alan Stern
2018-08-04 19:19 ` Guenter Roeck
2018-08-05 18:31 ` Alan Stern
2018-08-05 21:38 ` Guenter Roeck
2018-08-06 8:33 ` Christoph Hellwig
2018-08-06 15:58 ` Guenter Roeck
2018-08-06 8:37 ` Christoph Hellwig [this message]
2018-08-06 16:03 ` Guenter Roeck
2018-08-07 7:25 ` Christoph Hellwig
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