From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id BF88E839ED; Wed, 14 Feb 2024 17:20:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707931256; cv=none; b=QF3/lu5wFsJl7ZsVBV7lGQa6rk8OYot1Piw+WT4cFMg4x7XuMUCuuIRfzme1r6IPHHdp6j5XDuu/Z/6JZ32MKNhmG+kLyDaHVTR5PuBJtKvmOieYbzCWSMxOEmusHhPtBbqSwlx360dOS3L6/EEgdGKBZvrklgCtnNQRvvgn5CQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707931256; c=relaxed/simple; bh=DRFlqUoQ+56jX8SosJW0HOg/C/81XeRHYKQhTNegNK0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=KmiWFU5gOpzYZYF5zo8ir6NnR8WPmhhn32J3RGDjCmmKHmZz8q6gEXgBTmIjFxA7+u5MauL7iUFSl4uQVhqSaUzYCt1kH8SIjJqCWJ1xMfqUSM8NkP2XNnPciHunhWDEoV/3q2cwi0QE1W7lxVvskmGiNNztENSs6485D9QiuUE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 22EF71FB; Wed, 14 Feb 2024 09:21:35 -0800 (PST) Received: from [10.57.47.86] (unknown [10.57.47.86]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 65B743F766; Wed, 14 Feb 2024 09:20:51 -0800 (PST) Message-ID: <893ad3a4-ba24-43cf-8200-b8cd7742622d@arm.com> Date: Wed, 14 Feb 2024 17:20:50 +0000 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v3 1/7] dma: compile-out DMA sync op calls when not used Content-Language: en-GB To: Alexander Lobakin , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Christoph Hellwig , Marek Szyprowski , Joerg Roedel , Will Deacon , Greg Kroah-Hartman , "Rafael J. Wysocki" , Magnus Karlsson , Maciej Fijalkowski , Alexander Duyck , bpf@vger.kernel.org, netdev@vger.kernel.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org References: <20240214162201.4168778-1-aleksander.lobakin@intel.com> <20240214162201.4168778-2-aleksander.lobakin@intel.com> From: Robin Murphy In-Reply-To: <20240214162201.4168778-2-aleksander.lobakin@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2024-02-14 4:21 pm, Alexander Lobakin wrote: > Some platforms do have DMA, but DMA there is always direct and coherent. > Currently, even on such platforms DMA sync operations are compiled and > called. > Add a new hidden Kconfig symbol, DMA_NEED_SYNC, and set it only when > either sync operations are needed or there is DMA ops or swiotlb > enabled. Set dma_need_sync() and dma_skip_sync() depending on this > symbol state and don't call sync ops when dma_skip_sync() is true. > The change allows for future optimizations of DMA sync calls depending > on compile-time or runtime conditions. > > Signed-off-by: Alexander Lobakin > --- > kernel/dma/Kconfig | 4 ++ > include/linux/dma-mapping.h | 80 +++++++++++++++++++++++++++++++------ > kernel/dma/mapping.c | 20 +++++----- > 3 files changed, 81 insertions(+), 23 deletions(-) > > diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig > index d62f5957f36b..1c9ff05b1ecb 100644 > --- a/kernel/dma/Kconfig > +++ b/kernel/dma/Kconfig > @@ -107,6 +107,10 @@ config DMA_BOUNCE_UNALIGNED_KMALLOC > bool > depends on SWIOTLB > > +config DMA_NEED_SYNC > + def_bool ARCH_HAS_SYNC_DMA_FOR_DEVICE || ARCH_HAS_SYNC_DMA_FOR_CPU || \ > + ARCH_HAS_SYNC_DMA_FOR_CPU_ALL || DMA_OPS || SWIOTLB I'm not sure DMA_OPS belongs here - several architectures have non-trivial ops without syncs, e.g. Alpha. > + > config DMA_RESTRICTED_POOL > bool "DMA Restricted Pool" > depends on OF && OF_RESERVED_MEM && SWIOTLB > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index 4a658de44ee9..6c7640441214 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -117,13 +117,13 @@ dma_addr_t dma_map_resource(struct device *dev, phys_addr_t phys_addr, > size_t size, enum dma_data_direction dir, unsigned long attrs); > void dma_unmap_resource(struct device *dev, dma_addr_t addr, size_t size, > enum dma_data_direction dir, unsigned long attrs); > -void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, size_t size, > +void __dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, size_t size, > enum dma_data_direction dir); > -void dma_sync_single_for_device(struct device *dev, dma_addr_t addr, > +void __dma_sync_single_for_device(struct device *dev, dma_addr_t addr, > size_t size, enum dma_data_direction dir); > -void dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, > +void __dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, > int nelems, enum dma_data_direction dir); > -void dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, > +void __dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, > int nelems, enum dma_data_direction dir); > void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle, > gfp_t flag, unsigned long attrs); > @@ -147,7 +147,7 @@ u64 dma_get_required_mask(struct device *dev); > bool dma_addressing_limited(struct device *dev); > size_t dma_max_mapping_size(struct device *dev); > size_t dma_opt_mapping_size(struct device *dev); > -bool dma_need_sync(struct device *dev, dma_addr_t dma_addr); > +bool __dma_need_sync(struct device *dev, dma_addr_t dma_addr); > unsigned long dma_get_merge_boundary(struct device *dev); > struct sg_table *dma_alloc_noncontiguous(struct device *dev, size_t size, > enum dma_data_direction dir, gfp_t gfp, unsigned long attrs); > @@ -195,19 +195,19 @@ static inline void dma_unmap_resource(struct device *dev, dma_addr_t addr, > size_t size, enum dma_data_direction dir, unsigned long attrs) > { > } > -static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, > - size_t size, enum dma_data_direction dir) > +static inline void __dma_sync_single_for_cpu(struct device *dev, > + dma_addr_t addr, size_t size, enum dma_data_direction dir) To me it would feel more logical to put all the wrappers inside the #ifdef CONFIG_HAS_DMA and not touch these stubs at all (what does it mean to skip an inline no-op?). Or in fact, if dma_skip_sync() is constant false for !HAS_DMA, then we could also just make the external function declarations unconditional and remove the stubs. Not a critical matter though, and I defer to whatever Christoph thinks is most maintainable. > { > } > -static inline void dma_sync_single_for_device(struct device *dev, > +static inline void __dma_sync_single_for_device(struct device *dev, > dma_addr_t addr, size_t size, enum dma_data_direction dir) > { > } > -static inline void dma_sync_sg_for_cpu(struct device *dev, > +static inline void __dma_sync_sg_for_cpu(struct device *dev, > struct scatterlist *sg, int nelems, enum dma_data_direction dir) > { > } > -static inline void dma_sync_sg_for_device(struct device *dev, > +static inline void __dma_sync_sg_for_device(struct device *dev, > struct scatterlist *sg, int nelems, enum dma_data_direction dir) > { > } > @@ -277,7 +277,7 @@ static inline size_t dma_opt_mapping_size(struct device *dev) > { > return 0; > } > -static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr) > +static inline bool __dma_need_sync(struct device *dev, dma_addr_t dma_addr) > { > return false; > } > @@ -348,18 +348,72 @@ static inline void dma_unmap_single_attrs(struct device *dev, dma_addr_t addr, > return dma_unmap_page_attrs(dev, addr, size, dir, attrs); > } > > +static inline void __dma_sync_single_range_for_cpu(struct device *dev, > + dma_addr_t addr, unsigned long offset, size_t size, > + enum dma_data_direction dir) > +{ > + __dma_sync_single_for_cpu(dev, addr + offset, size, dir); > +} > + > +static inline void __dma_sync_single_range_for_device(struct device *dev, > + dma_addr_t addr, unsigned long offset, size_t size, > + enum dma_data_direction dir) > +{ > + __dma_sync_single_for_device(dev, addr + offset, size, dir); > +} There is no need to introduce these two. > + > +static inline bool dma_skip_sync(const struct device *dev) > +{ > + return !IS_ENABLED(CONFIG_DMA_NEED_SYNC); > +} > + > +static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr) > +{ > + return !dma_skip_sync(dev) ? __dma_need_sync(dev, dma_addr) : false; > +} That's a bit of a mind-bender... is it actually just return !dma_skip_sync(dev) && __dma_need_sync(dev, dma_addr); ? (I do still think the negative flag makes it all a little harder to follow in general than a positive "device needs to consider syncs" flag would.) > +static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, > + size_t size, enum dma_data_direction dir) > +{ > + if (!dma_skip_sync(dev)) > + __dma_sync_single_for_cpu(dev, addr, size, dir); > +} > + > +static inline void dma_sync_single_for_device(struct device *dev, > + dma_addr_t addr, size_t size, enum dma_data_direction dir) > +{ > + if (!dma_skip_sync(dev)) > + __dma_sync_single_for_device(dev, addr, size, dir); > +} > + > +static inline void dma_sync_sg_for_cpu(struct device *dev, > + struct scatterlist *sg, int nelems, enum dma_data_direction dir) > +{ > + if (!dma_skip_sync(dev)) > + __dma_sync_sg_for_cpu(dev, sg, nelems, dir); > +} > + > +static inline void dma_sync_sg_for_device(struct device *dev, > + struct scatterlist *sg, int nelems, enum dma_data_direction dir) > +{ > + if (!dma_skip_sync(dev)) > + __dma_sync_sg_for_device(dev, sg, nelems, dir); > +} > + > static inline void dma_sync_single_range_for_cpu(struct device *dev, > dma_addr_t addr, unsigned long offset, size_t size, > enum dma_data_direction dir) > { > - return dma_sync_single_for_cpu(dev, addr + offset, size, dir); > + if (!dma_skip_sync(dev)) > + __dma_sync_single_for_cpu(dev, addr + offset, size, dir); > } > > static inline void dma_sync_single_range_for_device(struct device *dev, > dma_addr_t addr, unsigned long offset, size_t size, > enum dma_data_direction dir) > { > - return dma_sync_single_for_device(dev, addr + offset, size, dir); > + if (!dma_skip_sync(dev)) > + __dma_sync_single_for_device(dev, addr + offset, size, dir); > } These two don't need changing either, since the dma_sync_single_* wrappers have already taken care of it. Thanks, Robin.