linux-kernel - Re: [PATCH 14/14] PCI/P2PDMA: Introduce pci_p2pdma_[un]map

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Date:   Tue, 23 Jul 2019 16:28:25 +0000
From:   "Koenig, Christian" <Christian.Koenig@....com>
To:     Logan Gunthorpe <logang@...tatee.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>
CC:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Christoph Hellwig <hch@....de>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...com>,
        Dan Williams <dan.j.williams@...el.com>,
        Eric Pilmore <epilmore@...aio.com>,
        Stephen Bates <sbates@...thlin.com>
Subject: Re: [PATCH 14/14] PCI/P2PDMA: Introduce pci_p2pdma_[un]map_resource()

Am 23.07.19 um 01:08 schrieb Logan Gunthorpe:
> pci_p2pdma_[un]map_resource() can be used to map a resource given
> it's physical address and the backing pci_dev. The functions will call
> dma_[un]map_resource() when appropriate.
>
> This is for demonstration purposes only as there are no users of this
> function at this time. Thus, this patch should not be merged at
> this time.
>
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>

Not sure if pci_p2pdma_phys_to_bus actually needs to be exported. But 
apart from that looks fine to me.

Reviewed-by: Christian König <christian.koenig@....com>

Christian.

> ---
>   drivers/pci/p2pdma.c | 85 ++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 85 insertions(+)
>
> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> index baf476039396..20c834cfd2d3 100644
> --- a/drivers/pci/p2pdma.c
> +++ b/drivers/pci/p2pdma.c
> @@ -874,6 +874,91 @@ void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
>   }
>   EXPORT_SYMBOL_GPL(pci_p2pdma_unmap_sg_attrs);
>   
> +static pci_bus_addr_t pci_p2pdma_phys_to_bus(struct pci_dev *dev,
> +		phys_addr_t start, size_t size)
> +{
> +	struct pci_host_bridge *bridge = pci_find_host_bridge(dev->bus);
> +	phys_addr_t end = start + size;
> +	struct resource_entry *window;
> +
> +	resource_list_for_each_entry(window, &bridge->windows) {
> +		if (window->res->start <= start && window->res->end >= end)
> +			return start - window->offset;
> +	}
> +
> +	return DMA_MAPPING_ERROR;
> +}
> +EXPORT_SYMBOL_GPL(pci_p2pdma_phys_to_bus);
> +
> +/**
> + * pci_p2pdma_map_resource - map a PCI peer-to-peer physical address for DMA
> + * @provider: pci device that provides the memory backed by phys_addr
> + * @dma_dev: device doing the DMA request
> + * @phys_addr: physical address of the memory to map
> + * @size: size of the memory to map
> + * @dir: DMA direction
> + * @attrs: dma attributes passed to dma_map_resource() (if called)
> + *
> + * Maps a BAR physical address for programming a DMA engine.
> + *
> + * Returns the dma_addr_t to map or DMA_MAPPING_ERROR on failure
> + */
> +dma_addr_t pci_p2pdma_map_resource(struct pci_dev *provider,
> +		struct device *dma_dev, phys_addr_t phys_addr, size_t size,
> +		enum dma_data_direction dir, unsigned long attrs)
> +{
> +	struct pci_dev *client;
> +	int dist;
> +
> +	client = find_parent_pci_dev(dma_dev);
> +	if (!client)
> +		return DMA_MAPPING_ERROR;
> +
> +	dist = upstream_bridge_distance(provider, client, NULL);
> +	if (dist & P2PDMA_NOT_SUPPORTED)
> +		return DMA_MAPPING_ERROR;
> +
> +	if (dist & P2PDMA_THRU_HOST_BRIDGE)
> +		return dma_map_resource(dma_dev, phys_addr, size, dir, attrs);
> +	else
> +		return pci_p2pdma_phys_to_bus(provider, phys_addr, size);
> +}
> +EXPORT_SYMBOL_GPL(pci_p2pdma_map_resource);
> +
> +/**
> + * pci_p2pdma_unmap_resource - unmap a resource mapped with
> + *		pci_p2pdma_map_resource()
> + * @provider: pci device that provides the memory backed by phys_addr
> + * @dma_dev: device doing the DMA request
> + * @addr: dma address returned by pci_p2pdma_unmap_resource()
> + * @size: size of the memory to map
> + * @dir: DMA direction
> + * @attrs: dma attributes passed to dma_unmap_resource() (if called)
> + *
> + * Maps a BAR physical address for programming a DMA engine.
> + *
> + * Returns the dma_addr_t to map or DMA_MAPPING_ERROR on failure
> + */
> +void pci_p2pdma_unmap_resource(struct pci_dev *provider,
> +		struct device *dma_dev, dma_addr_t addr, size_t size,
> +		enum dma_data_direction dir, unsigned long attrs)
> +{
> +	struct pci_dev *client;
> +	int dist;
> +
> +	client = find_parent_pci_dev(dma_dev);
> +	if (!client)
> +		return;
> +
> +	dist = upstream_bridge_distance(provider, client, NULL);
> +	if (dist & P2PDMA_NOT_SUPPORTED)
> +		return;
> +
> +	if (dist & P2PDMA_THRU_HOST_BRIDGE)
> +		dma_unmap_resource(dma_dev, addr, size, dir, attrs);
> +}
> +EXPORT_SYMBOL_GPL(pci_p2pdma_unmap_resource);
> +
>   /**
>    * pci_p2pdma_enable_store - parse a configfs/sysfs attribute store
>    *		to enable p2pdma