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SubjectRe: [PATCH v2 09/14] device core: Add ability to handle multiple dma offsets
Hello Andy,

On Tue, May 26, 2020 at 4:54 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> 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_?!

Yes, otherwise if the device gets unbound/bound repeatedly then there
would be a memory leak.

>
>
> Looking at r_size it should be rather kcalloc().

Yep.
>
>
> > + 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.

Okay, will change. I was trying to keep the comment style of the other
variables.

> > +#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
>
Okay.

>
> > + 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) {
> ...
> }
>
> ?
>
That won't work; 'm' is either null or a valid pointer to an array
which has an additional entry that is 0-filled.. If non-null, 'm'
will never turn into NULL via 'm++' and the while loop will not
terminate.
>
>
> > + 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.

Okay.
>
> > + 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


Thanks!
Jim Quinlan

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