From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e39.co.us.ibm.com (e39.co.us.ibm.com [32.97.110.160]) (using TLSv1 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id A59EC1A0475 for ; Wed, 28 Oct 2015 09:27:13 +1100 (AEDT) Received: from localhost by e39.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 27 Oct 2015 16:27:11 -0600 Received: from b03cxnp08025.gho.boulder.ibm.com (b03cxnp08025.gho.boulder.ibm.com [9.17.130.17]) by d03dlp01.boulder.ibm.com (Postfix) with ESMTP id 23CC01FF002D for ; Tue, 27 Oct 2015 16:15:22 -0600 (MDT) Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by b03cxnp08025.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t9RMPkMP2425276 for ; Tue, 27 Oct 2015 15:25:46 -0700 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t9RMR752004598 for ; Tue, 27 Oct 2015 16:27:10 -0600 Date: Tue, 27 Oct 2015 15:27:06 -0700 From: Nishanth Aravamudan To: Alexey Kardashevskiy Cc: Michael Ellerman , Matthew Wilcox , Keith Busch , Benjamin Herrenschmidt , Paul Mackerras , David Gibson , Christoph Hellwig , "David S. Miller" , 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 Message-ID: <20151027222706.GF7716@linux.vnet.ibm.com> References: <20151023205420.GA10197@linux.vnet.ibm.com> <20151023205718.GC10197@linux.vnet.ibm.com> <562F1368.1030204@ozlabs.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <562F1368.1030204@ozlabs.ru> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 27.10.2015 [17:02:16 +1100], Alexey Kardashevskiy wrote: > On 10/24/2015 07:57 AM, Nishanth Aravamudan wrote: > >On Power, the kernel's page size can differ from the IOMMU's page size, > >so we need to override the generic implementation, which always returns > >the kernel's page size. Lookup the IOMMU's page size from struct > >iommu_table, if available. Fallback to the kernel's page size, > >otherwise. > > > >Signed-off-by: Nishanth Aravamudan > >--- > > arch/powerpc/include/asm/dma-mapping.h | 3 +++ > > arch/powerpc/kernel/dma.c | 9 +++++++++ > > 2 files changed, 12 insertions(+) > > > >diff --git a/arch/powerpc/include/asm/dma-mapping.h b/arch/powerpc/include/asm/dma-mapping.h > >index 7f522c0..c5638f4 100644 > >--- a/arch/powerpc/include/asm/dma-mapping.h > >+++ b/arch/powerpc/include/asm/dma-mapping.h > >@@ -125,6 +125,9 @@ static inline void set_dma_offset(struct device *dev, dma_addr_t off) > > #define HAVE_ARCH_DMA_SET_MASK 1 > > extern int dma_set_mask(struct device *dev, u64 dma_mask); > > > >+#define HAVE_ARCH_DMA_GET_PAGE_SHIFT 1 > >+extern unsigned long dma_get_page_shift(struct device *dev); > >+ > > #include > > > > extern int __dma_set_mask(struct device *dev, u64 dma_mask); > >diff --git a/arch/powerpc/kernel/dma.c b/arch/powerpc/kernel/dma.c > >index 59503ed..e805af2 100644 > >--- a/arch/powerpc/kernel/dma.c > >+++ b/arch/powerpc/kernel/dma.c > >@@ -335,6 +335,15 @@ int dma_set_mask(struct device *dev, u64 dma_mask) > > } > > EXPORT_SYMBOL(dma_set_mask); > > > >+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? Right, so the logic of my series, goes like this: a) We currently are assuming DMA_PAGE_SHIFT (conceptual constant) is PAGE_SHIFT everywhere, including Power. b) After 2/7, the Power code will return either the IOMMU table's shift value, if set, or PAGE_SHIFT (I guess this would be the case if get_dma_ops(dev) == &dma_direct_ops, as you said). That is no different than we have now, except we can return the accurate IOMMU value if available. 3) After 3/7, the platform can override the generic Power get_dma_page_shift(). 4) After 4/7, pseries will return the DDW value, if available, then fallback to the IOMMU table's value. I think in the case of get_dma_ops(dev)==&dma_direct_ops, the only way that can happen is if we are using DDW, right? -Nish