Re: [PATCH v2 09/14] device core: Add ability to handle multiple dma offsets

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Tue, May 26, 2020 at 03:12:48PM -0400, Jim Quinlan wrote:
> The new field in struct device 'dma_pfn_offset_map' is used to facilitate
> the use of multiple pfn offsets between cpu addrs and dma addrs.  It is
> similar to 'dma_pfn_offset' except that the offset chosen depends on the
> cpu or dma address involved.
> 
> Signed-off-by: Jim Quinlan <james.quinlan@broadcom.com>
> ---
>  drivers/of/address.c        | 65 +++++++++++++++++++++++++++++++++++--
>  drivers/usb/core/message.c  |  3 ++
>  drivers/usb/core/usb.c      |  3 ++
>  include/linux/device.h      | 10 +++++-
>  include/linux/dma-direct.h  | 10 ++++--
>  include/linux/dma-mapping.h | 46 ++++++++++++++++++++++++++
>  kernel/dma/Kconfig          | 13 ++++++++
>  7 files changed, 144 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/of/address.c b/drivers/of/address.c
> index 96d8cfb14a60..a01afffcde7d 100644
> --- a/drivers/of/address.c
> +++ b/drivers/of/address.c
> @@ -918,6 +918,47 @@ void __iomem *of_io_request_and_map(struct device_node *np, int index,
>  }
>  EXPORT_SYMBOL(of_io_request_and_map);
>  
> +#ifdef CONFIG_DMA_PFN_OFFSET_MAP
> +static int attach_dma_pfn_offset_map(struct device *dev,
> +				     struct device_node *node, int num_ranges)
> +{
> +	struct of_range_parser parser;
> +	struct of_range range;
> +	size_t r_size = (num_ranges + 1)
> +		* sizeof(struct dma_pfn_offset_region);
> +	struct dma_pfn_offset_region *r;
> +

> +	r = devm_kzalloc(dev, r_size, GFP_KERNEL);

devm_?!

Looking at r_size it should be rather kcalloc().

> +	if (!r)
> +		return -ENOMEM;
> +	dev->dma_pfn_offset_map = r;
> +	of_dma_range_parser_init(&parser, node);
> +
> +	/*
> +	 * Record all info for DMA ranges array.  We could
> +	 * just use the of_range struct, but if we did that it
> +	 * would require more calculations for phys_to_dma and
> +	 * dma_to_phys conversions.
> +	 */
> +	for_each_of_range(&parser, &range) {
> +		r->cpu_beg = range.cpu_addr;
> +		r->cpu_end = r->cpu_beg + range.size;
> +		r->dma_beg = range.bus_addr;
> +		r->dma_end = r->dma_beg + range.size;
> +		r->pfn_offset = PFN_DOWN(range.cpu_addr)
> +			- PFN_DOWN(range.bus_addr);
> +		r++;
> +	}
> +	return 0;
> +}
> +#else
> +static int attach_dma_pfn_offset_map(struct device *dev,
> +				     struct device_node *node, int num_ranges)
> +{
> +	return 0;
> +}
> +#endif
> +
>  /**
>   * of_dma_get_range - Get DMA range info
>   * @dev:	device pointer; only needed for a corner case.
> @@ -947,6 +988,8 @@ int of_dma_get_range(struct device *dev, struct device_node *np, u64 *dma_addr,
>  	struct of_range_parser parser;
>  	struct of_range range;
>  	u64 dma_start = U64_MAX, dma_end = 0, dma_offset = 0;
> +	bool dma_multi_pfn_offset = false;
> +	int num_ranges = 0;
>  
>  	while (node) {
>  		ranges = of_get_property(node, "dma-ranges", &len);
> @@ -977,10 +1020,19 @@ int of_dma_get_range(struct device *dev, struct device_node *np, u64 *dma_addr,
>  		pr_debug("dma_addr(%llx) cpu_addr(%llx) size(%llx)\n",
>  			 range.bus_addr, range.cpu_addr, range.size);
>  
> +		num_ranges++;
>  		if (dma_offset && range.cpu_addr - range.bus_addr != dma_offset) {
> -			pr_warn("Can't handle multiple dma-ranges with different offsets on node(%pOF)\n", node);
> -			/* Don't error out as we'd break some existing DTs */
> -			continue;
> +			if (!IS_ENABLED(CONFIG_DMA_PFN_OFFSET_MAP)) {
> +				pr_warn("Can't handle multiple dma-ranges with different offsets on node(%pOF)\n", node);
> +				pr_warn("Perhaps set DMA_PFN_OFFSET_MAP=y?\n");
> +				/*
> +				 * Don't error out as we'd break some existing
> +				 * DTs that are using configs w/o
> +				 * CONFIG_DMA_PFN_OFFSET_MAP set.
> +				 */
> +				continue;
> +			}
> +			dma_multi_pfn_offset = true;
>  		}
>  		dma_offset = range.cpu_addr - range.bus_addr;
>  
> @@ -991,6 +1043,13 @@ int of_dma_get_range(struct device *dev, struct device_node *np, u64 *dma_addr,
>  			dma_end = range.bus_addr + range.size;
>  	}
>  
> +	if (dma_multi_pfn_offset) {
> +		dma_offset = 0;
> +		ret = attach_dma_pfn_offset_map(dev, node, num_ranges);
> +		if (ret)
> +			return ret;
> +	}
> +
>  	if (dma_start >= dma_end) {
>  		ret = -EINVAL;
>  		pr_debug("Invalid DMA ranges configuration on node(%pOF)\n",
> diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
> index 6197938dcc2d..aaa3e58f5eb4 100644
> --- a/drivers/usb/core/message.c
> +++ b/drivers/usb/core/message.c
> @@ -1960,6 +1960,9 @@ int usb_set_configuration(struct usb_device *dev, int configuration)
>  		 */
>  		intf->dev.dma_mask = dev->dev.dma_mask;
>  		intf->dev.dma_pfn_offset = dev->dev.dma_pfn_offset;
> +#ifdef CONFIG_DMA_PFN_OFFSET_MAP
> +		intf->dev.dma_pfn_offset_map = dev->dev.dma_pfn_offset_map;
> +#endif
>  		INIT_WORK(&intf->reset_ws, __usb_queue_reset_device);
>  		intf->minor = -1;
>  		device_initialize(&intf->dev);
> diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
> index f16c26dc079d..d2ed4d90e56e 100644
> --- a/drivers/usb/core/usb.c
> +++ b/drivers/usb/core/usb.c
> @@ -612,6 +612,9 @@ struct usb_device *usb_alloc_dev(struct usb_device *parent,
>  	 */
>  	dev->dev.dma_mask = bus->sysdev->dma_mask;
>  	dev->dev.dma_pfn_offset = bus->sysdev->dma_pfn_offset;
> +#ifdef CONFIG_DMA_PFN_OFFSET_MAP
> +	dev->dev.dma_pfn_offset_map = bus->sysdev->dma_pfn_offset_map;
> +#endif
>  	set_dev_node(&dev->dev, dev_to_node(bus->sysdev));
>  	dev->state = USB_STATE_ATTACHED;
>  	dev->lpm_disable_count = 1;
> diff --git a/include/linux/device.h b/include/linux/device.h
> index ac8e37cd716a..67a240ad4fc5 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -493,6 +493,8 @@ struct dev_links_info {
>   * @bus_dma_limit: Limit of an upstream bridge or bus which imposes a smaller
>   *		DMA limit than the device itself supports.
>   * @dma_pfn_offset: offset of DMA memory range relatively of RAM
> + * @dma_pfn_offset_map:	Like dma_pfn_offset but used when there are multiple
> + *		pfn offsets for multiple dma-ranges.
>   * @dma_parms:	A low level driver may set these to teach IOMMU code about
>   * 		segment limitations.
>   * @dma_pools:	Dma pools (if dma'ble device).
> @@ -578,7 +580,13 @@ struct device {
>  					     allocations such descriptors. */
>  	u64		bus_dma_limit;	/* upstream dma constraint */
>  	unsigned long	dma_pfn_offset;
> -
> +#ifdef CONFIG_DMA_PFN_OFFSET_MAP
> +	const struct dma_pfn_offset_region *dma_pfn_offset_map;

> +					/* Like dma_pfn_offset, but for
> +					 * the unlikely case of multiple
> +					 * offsets. If non-null, dma_pfn_offset
> +					 * will be set to 0. */

A bit harder to read comment indented too much and located after the declared variable.

> +#endif
>  	struct device_dma_parameters *dma_parms;
>  
>  	struct list_head	dma_pools;	/* dma pools (if dma'ble) */
> diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
> index 24b8684aa21d..03110a57eabc 100644
> --- a/include/linux/dma-direct.h
> +++ b/include/linux/dma-direct.h
> @@ -14,15 +14,21 @@ extern unsigned int zone_dma_bits;
>  static inline dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t paddr)
>  {
>  	dma_addr_t dev_addr = (dma_addr_t)paddr;
> +	/* The compiler should remove the 2nd term if !DMA_PFN_OFFSET_MAP */
> +	unsigned long dma_pfn_offset = dev->dma_pfn_offset
> +		+ dma_pfn_offset_from_phys_addr(dev, paddr);
>  
> -	return dev_addr - ((dma_addr_t)dev->dma_pfn_offset << PAGE_SHIFT);
> +	return dev_addr - ((dma_addr_t)dma_pfn_offset << PAGE_SHIFT);
>  }
>  
>  static inline phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t dev_addr)
>  {
>  	phys_addr_t paddr = (phys_addr_t)dev_addr;
> +	/* The compiler should remove the 2nd term if !DMA_PFN_OFFSET_MAP */
> +	unsigned long dma_pfn_offset = dev->dma_pfn_offset
> +		+ dma_pfn_offset_from_dma_addr(dev, paddr);
>  
> -	return paddr + ((phys_addr_t)dev->dma_pfn_offset << PAGE_SHIFT);
> +	return paddr + ((phys_addr_t)dma_pfn_offset << PAGE_SHIFT);
>  }
>  #endif /* !CONFIG_ARCH_HAS_PHYS_TO_DMA */
>  
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index 330ad58fbf4d..91940bba2229 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -256,6 +256,52 @@ static inline void dma_direct_sync_sg_for_cpu(struct device *dev,
>  size_t dma_direct_max_mapping_size(struct device *dev);
>  
>  #ifdef CONFIG_HAS_DMA
> +#ifdef CONFIG_DMA_PFN_OFFSET_MAP
> +struct dma_pfn_offset_region {

> +	phys_addr_t	cpu_beg;
> +	phys_addr_t	cpu_end;
> +	dma_addr_t	dma_beg;
> +	dma_addr_t	dma_end;

Perhaps
	s,beg,start,
in above names

> +	unsigned long	pfn_offset;
> +};
> +
> +static inline unsigned long dma_pfn_offset_from_dma_addr(struct device *dev,
> +							 dma_addr_t dma_addr)
> +{
> +	const struct dma_pfn_offset_region *m = dev->dma_pfn_offset_map;

> +	if (m)
> +		for (; m->cpu_end; m++)

Why not simple

	while (m) {
		...
	}

?


> +			if (dma_addr >= m->dma_beg && dma_addr < m->dma_end)
> +				return m->pfn_offset;
> +	return 0;
> +}
> +
> +static inline unsigned long dma_pfn_offset_from_phys_addr(struct device *dev,
> +							  phys_addr_t paddr)
> +{
> +	const struct dma_pfn_offset_region *m = dev->dma_pfn_offset_map;
> +

> +	if (m)
> +		for (; m->cpu_end; m++)

Ditto.

> +			if (paddr >= m->cpu_beg && paddr < m->cpu_end)
> +				return m->pfn_offset;
> +	return 0;
> +}
> +#else  /* CONFIG_DMA_PFN_OFFSET_MAP */
> +static inline unsigned long dma_pfn_offset_from_dma_addr(struct device *dev,
> +							 dma_addr_t dma_addr)
> +{
> +	return 0;
> +}
> +
> +static inline unsigned long dma_pfn_offset_from_phys_addr(struct device *dev,
> +							  phys_addr_t paddr)
> +{
> +	return 0;
> +}
> +#endif /* CONFIG_DMA_PFN_OFFSET_MAP */
> +
>  #include <asm/dma-mapping.h>
>  
>  static inline const struct dma_map_ops *get_dma_ops(struct device *dev)
> diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
> index 4c103a24e380..ceb7e5e8f501 100644
> --- a/kernel/dma/Kconfig
> +++ b/kernel/dma/Kconfig
> @@ -195,3 +195,16 @@ config DMA_API_DEBUG_SG
>  	  is technically out-of-spec.
>  
>  	  If unsure, say N.
> +
> +config DMA_PFN_OFFSET_MAP
> +	bool "Uses a DMA range map to calculate PFN offset"
> +	depends on PCIE_BRCMSTB

> +	default n

Redundant.

> +	help
> +	  Some devices have a dma-range that gets converted to
> +	  a dev->dma_pfn_offset value.  This option is for the
> +	  atypical case of there being multiple dma-ranges requiring
> +	  multiple pfn offsets, which are selected from when
> +	  converting to phys to dma and vice versa.
> +
> +	  If unsure, say N.
> -- 
> 2.17.1
> 

-- 
With Best Regards,
Andy Shevchenko


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