From: "Busch, Keith" <keith.busch@intel.com>
To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Matthew Wilcox <willy@linux.intel.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
David Gibson <david@gibson.dropbear.id.au>,
Christoph Hellwig <hch@infradead.org>,
"David S. Miller" <davem@davemloft.net>,
linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org
Subject: Re: [PATCH 2/7 v2] powerpc/dma-mapping: override dma_get_page_shift
Date: Tue, 27 Oct 2015 14:06:47 +0000 [thread overview]
Message-ID: <20151027140647.GA15583@localhost.localdomain> (raw)
In-Reply-To: <562F1368.1030204@ozlabs.ru>
On Tue, Oct 27, 2015 at 05:02:16PM +1100, Alexey Kardashevskiy wrote:
> >+unsigned long dma_get_page_shift(struct device *dev)
> >+{
> >+ struct iommu_table *tbl = get_iommu_table_base(dev);
> >+ if (tbl)
> >+ return tbl->it_page_shift;
>
>
> All PCI devices have this initialized on POWER (at least, our, IBM's
> POWER) so 4K will always be returned here while in the case of
> (get_dma_ops(dev)==&dma_direct_ops) it could actually return
> PAGE_SHIFT. Is 4K still preferred value to return here?
4k is always a safe option to return, but ideally you want to return the
highest guaranteed DMA address alignment. The driver just needs to know
which bits to mask from virtual addresses such that the offset is the
same as the DMA address.
next prev parent reply other threads:[~2015-10-27 14:09 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-23 20:54 [PATCH 0/5 v3] Fix NVMe driver support on Power with 32-bit DMA Nishanth Aravamudan
2015-10-23 20:56 ` [PATCH 1/7 v3] dma-mapping: add generic dma_get_page_shift API Nishanth Aravamudan
2015-10-23 20:57 ` [PATCH 2/7 v2] powerpc/dma-mapping: override dma_get_page_shift Nishanth Aravamudan
2015-10-27 6:02 ` Alexey Kardashevskiy
2015-10-27 14:06 ` Busch, Keith [this message]
2015-10-27 22:27 ` Nishanth Aravamudan
2015-10-28 1:00 ` Alexey Kardashevskiy
2015-10-28 1:54 ` Nishanth Aravamudan
2015-10-28 2:20 ` Benjamin Herrenschmidt
2015-10-28 2:30 ` Nishanth Aravamudan
2015-10-28 3:20 ` Benjamin Herrenschmidt
2015-10-23 20:57 ` [PATCH 0/5 v3] Fix NVMe driver support on Power with 32-bit DMA Nishanth Aravamudan
2015-10-23 20:58 ` [PATCH 3/7 v2] powerpc/dma: implement per-platform dma_get_page_shift Nishanth Aravamudan
2015-10-23 20:59 ` [PATCH 4/7 v2] pseries/iommu: implement DDW-aware dma_get_page_shift Nishanth Aravamudan
2015-10-27 5:56 ` Alexey Kardashevskiy
2015-10-27 22:22 ` Nishanth Aravamudan
2015-10-23 21:00 ` [PATCH 5/7] [RFC PATCH 5/7] sparc: rename kernel/iommu_common.h -> include/asm/iommu_common.h Nishanth Aravamudan
2015-10-23 21:02 ` Nishanth Aravamudan
2015-10-23 21:01 ` [RFC PATCH 6/7] sparc/dma-mapping: override dma_get_page_shift Nishanth Aravamudan
2015-10-23 21:02 ` [PATCH 7/7 v2] drivers/nvme: default to the IOMMU page size Nishanth Aravamudan
2015-10-27 1:27 ` [PATCH 0/5 v3] Fix NVMe driver support on Power with 32-bit DMA David Miller
2015-10-27 22:20 ` Nishanth Aravamudan
2015-10-27 22:36 ` Busch, Keith
2015-10-28 0:54 ` David Miller
2015-10-28 13:59 ` Busch, Keith
2015-10-29 11:55 ` Christoph Hellwig
2015-10-29 15:57 ` Nishanth Aravamudan
2015-10-29 17:20 ` Busch, Keith
2015-10-30 21:35 ` [PATCH 1/1 v3] drivers/nvme: default to 4k device page size Nishanth Aravamudan
2015-10-30 21:48 ` Keith Busch
2015-10-30 22:13 ` Nishanth Aravamudan
2015-11-03 13:18 ` Christoph Hellwig
2015-11-03 13:46 ` Keith Busch
2015-11-05 17:01 ` [PATCH 1/1 v4] " Nishanth Aravamudan
2015-11-05 19:58 ` Christoph Hellwig
2015-11-05 21:54 ` Nishanth Aravamudan
2015-11-06 16:13 ` Nishanth Aravamudan
2015-11-13 7:37 ` Christoph Hellwig
2015-11-13 15:08 ` Keith Busch
2015-11-18 14:42 ` Christoph Hellwig
2015-10-30 1:49 ` [PATCH 0/5 v3] Fix NVMe driver support on Power with 32-bit DMA David Miller
2015-10-30 21:35 ` Nishanth Aravamudan
2015-10-27 22:57 ` Julian Calaby
2015-10-27 23:40 ` Nishanth Aravamudan
2015-10-27 23:43 ` Julian Calaby
2015-10-28 0:29 ` Benjamin Herrenschmidt
2015-10-28 1:00 ` David Miller
2015-10-28 0:53 ` David Miller
2015-10-28 1:52 ` Nishanth Aravamudan
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