[PATCH v9 08/12] device core: Introduce DMA range map, supplanting dma_pfn_offset

[Jim Quinlan]

On Sat, Aug 1, 2020 at 1:17 PM Nicolas Saenz Julienne
<nsaenzjulienne at suse.de> wrote:
>
> Hi Jim, here's some comments after testing your series against RPi4.
>
> On Fri, 2020-07-24 at 16:33 -0400, Jim Quinlan wrote:
> > The new field 'dma_range_map' in struct device is used to facilitate the
> > use of single or multiple offsets between mapping regions of cpu addrs and
> > dma addrs.  It subsumes the role of "dev->dma_pfn_offset" which was only
> > capable of holding a single uniform offset and had no region bounds
> > checking.
> >
> > The function of_dma_get_range() has been modified so that it takes a single
> > argument -- the device node -- and returns a map, NULL, or an error code.
> > The map is an array that holds the information regarding the DMA regions.
> > Each range entry contains the address offset, the cpu_start address, the
> > dma_start address, and the size of the region.
> >
> > of_dma_configure() is the typical manner to set range offsets but there are
> > a number of ad hoc assignments to "dev->dma_pfn_offset" in the kernel
> > driver code.  These cases now invoke the function
> > dma_attach_offset_range(dev, cpu_addr, dma_addr, size).
> >
> > Signed-off-by: Jim Quinlan <james.quinlan at broadcom.com>
> > ---
>
> [...]
>
> > diff --git a/drivers/of/address.c b/drivers/of/address.c
> > index 8eea3f6e29a4..4b718d199efe 100644
> > --- a/drivers/of/address.c
> > +++ b/drivers/of/address.c
> > @@ -918,33 +918,33 @@ void __iomem *of_io_request_and_map(struct device_node *np, int index,
> >  }
> >  EXPORT_SYMBOL(of_io_request_and_map);
> >
> > +#ifdef CONFIG_HAS_DMA
> >  /**
> > - * of_dma_get_range - Get DMA range info
> > + * of_dma_get_range - Get DMA range info and put it into a map array
> >   * @np:              device node to get DMA range info
> > - * @dma_addr:        pointer to store initial DMA address of DMA range
> > - * @paddr:   pointer to store initial CPU address of DMA range
> > - * @size:    pointer to store size of DMA range
> > + * @map:     dma range structure to return
> >   *
> >   * Look in bottom up direction for the first "dma-ranges" property
> > - * and parse it.
> > - *  dma-ranges format:
> > + * and parse it.  Put the information into a DMA offset map array.
> > + *
> > + * dma-ranges format:
> >   *   DMA addr (dma_addr)     : naddr cells
> >   *   CPU addr (phys_addr_t)  : pna cells
> >   *   size                    : nsize cells
> >   *
> > - * It returns -ENODEV if "dma-ranges" property was not found
> > - * for this device in DT.
> > + * It returns -ENODEV if "dma-ranges" property was not found for this
> > + * device in the DT.
> >   */
> > -int of_dma_get_range(struct device_node *np, u64 *dma_addr, u64 *paddr, u64 *size)
> > +int of_dma_get_range(struct device_node *np, const struct bus_dma_region **map)
> >  {
> >       struct device_node *node = of_node_get(np);
> >       const __be32 *ranges = NULL;
> > -     int len;
> > -     int ret = 0;
> >       bool found_dma_ranges = false;
> >       struct of_range_parser parser;
> >       struct of_range range;
> > -     u64 dma_start = U64_MAX, dma_end = 0, dma_offset = 0;
> > +     struct bus_dma_region *r;
> > +     int len, num_ranges = 0;
> > +     int ret;
> >
> >       while (node) {
> >               ranges = of_get_property(node, "dma-ranges", &len);
> > @@ -970,44 +970,35 @@ int of_dma_get_range(struct device_node *np, u64 *dma_addr, u64 *paddr, u64 *siz
> >       }
> >
> >       of_dma_range_parser_init(&parser, node);
> > +     for_each_of_range(&parser, &range)
> > +             num_ranges++;
> > +
> > +     of_dma_range_parser_init(&parser, node);
> > +
> > +     ret = -ENOMEM;
> > +     r = kcalloc(num_ranges + 1, sizeof(*r), GFP_KERNEL);
> > +     if (!r)
> > +             goto out;
> >
> > +     /*
> > +      * Record all info in the generic DMA ranges array for struct device.
> > +      */
> > +     *map = r;
> >       for_each_of_range(&parser, &range) {
> >               pr_debug("dma_addr(%llx) cpu_addr(%llx) size(%llx)\n",
> >                        range.bus_addr, range.cpu_addr, range.size);
> > -
> > -             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;
> > -             }
> > -             dma_offset = range.cpu_addr - range.bus_addr;
> > -
> > -             /* Take lower and upper limits */
> > -             if (range.bus_addr < dma_start)
> > -                     dma_start = range.bus_addr;
> > -             if (range.bus_addr + range.size > dma_end)
> > -                     dma_end = range.bus_addr + range.size;
> > -     }
> > -
> > -     if (dma_start >= dma_end) {
> > -             ret = -EINVAL;
> > -             pr_debug("Invalid DMA ranges configuration on node(%pOF)\n",
> > -                      node);
> > -             goto out;
> > +             r->cpu_start = range.cpu_addr;
> > +             r->dma_start = range.bus_addr;
> > +             r->size = range.size;
> > +             r->offset = (u64)range.cpu_addr - (u64)range.bus_addr;
> > +             r++;
> >       }
> >
> > -     *dma_addr = dma_start;
> > -     *size = dma_end - dma_start;
> > -     *paddr = dma_start + dma_offset;
> > -
> > -     pr_debug("final: dma_addr(%llx) cpu_addr(%llx) size(%llx)\n",
> > -              *dma_addr, *paddr, *size);
> > -
>
> I think you're missing here:
>
>         ret = 0;
Yes.  It somehow passed my tests because it still sets dev->dma_range_map.

Thanks again,
Jiom

>
> >  out:
> >       of_node_put(node);
> > -
> >       return ret;
> >  }
>
> Regards,
> Nicolas
>