From: Christoph Hellwig <hch@infradead.org>
To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: Sam Bobroff <sbobroff@linux.ibm.com>,
Alistair Popple <alistair@popple.id.au>,
Oliver O'Halloran <oohall@gmail.com>,
linuxppc-dev@lists.ozlabs.org,
David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [PATCH kernel v4 0/4 repost] powerpc/ioda2: Yet another attempt to allow DMA masks between 32 and 59
Date: Fri, 12 Jul 2019 08:28:00 -0700 [thread overview]
Message-ID: <20190712152800.GC3061@infradead.org> (raw)
In-Reply-To: <20190712094509.56695-1-aik@ozlabs.ru>
On Fri, Jul 12, 2019 at 07:45:05PM +1000, Alexey Kardashevskiy wrote:
> This is an attempt to allow DMA masks between 32..59 which are not large
> enough to use either a PHB3 bypass mode or a sketchy bypass. Depending
> on the max order, up to 40 is usually available.
Can you elaborate what you man with supported in detail? In the end
a DMA devices DMA capability is only really interesting as a lower
bound.
e.g. if you have a DMA that supports 40-bit DMA addressing we could
always treat it as if supports 32-bit addressing, and I thought the
powerpc code does that, as the DMA API now relies on that. Did I miss
something and it explicitly rejected that (in which case I didn't spot
the fix in this series), or is this just an optimization to handle these
devices more optimally, in which case maybe the changelog could be
improved a bit.
next prev parent reply other threads:[~2019-07-12 15:38 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-12 9:45 [PATCH kernel v4 0/4 repost] powerpc/ioda2: Yet another attempt to allow DMA masks between 32 and 59 Alexey Kardashevskiy
2019-07-12 9:45 ` [PATCH kernel v4 1/4] powerpc/powernv/ioda: Fix race in TCE level allocation Alexey Kardashevskiy
2019-07-12 9:45 ` [PATCH kernel v4 2/4] powerpc/iommu: Allow bypass-only for DMA Alexey Kardashevskiy
2019-07-12 15:20 ` Christoph Hellwig
2019-07-15 8:33 ` Alexey Kardashevskiy
2019-07-15 12:35 ` Christoph Hellwig
2019-07-12 9:45 ` [PATCH kernel v4 3/4] powerpc/powernv/ioda2: Allocate TCE table levels on demand for default DMA window Alexey Kardashevskiy
2019-07-12 9:45 ` [PATCH kernel v4 4/4] powerpc/powernv/ioda2: Create bigger default window with 64k IOMMU pages Alexey Kardashevskiy
2019-07-12 15:25 ` Christoph Hellwig
2019-07-12 15:28 ` Christoph Hellwig [this message]
2019-07-15 8:43 ` [PATCH kernel v4 0/4 repost] powerpc/ioda2: Yet another attempt to allow DMA masks between 32 and 59 Alexey Kardashevskiy
2019-07-15 12:39 ` Christoph Hellwig
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