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Date: Sat, 6 Aug 2022 14:13:12 +0800
From: Jianmin Lv <lvjianmin@...ngson.cn>
To: Robin Murphy <robin.murphy@....com>, lpieralisi@...nel.org,
guohanjun@...wei.com, sudeep.holla@....com, rafael@...nel.org,
lenb@...nel.org, robert.moore@...el.com
Cc: linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH V2 1/2] ACPI / scan: Support multiple dma windows with
different offsets
On 2022/8/5 下午8:46, Robin Murphy wrote:
> On 2022-08-05 08:31, Jianmin Lv wrote:
>> For DT, of_dma_get_range returns bus_dma_region typed dma regions,
>> which makes multiple dma windows with different offset available
>> for translation between dma address and cpu address.
>>
>> But for ACPI, acpi_dma_get_range doesn't return similar dma regions,
>> causing no path for setting dev->dma_range_map conveniently. So the
>> patch changes acpi_dma_get_range and returns bus_dma_region typed
>> dma regions according to of_dma_get_range.
>>
>> After changing acpi_dma_get_range, acpi_arch_dma_setup is changed for
>> ARM64, where original dma_addr and size are removed, and pass 0 and
>> U64_MAX for dma_base and size of arch_setup_dma_ops.
>
> Hmm, I realise the reasoning behind this exists largely in my head, so
> for the benefit of everyone else we should perhaps clarify that these
> arguments are now redundant, so this is a simplification consistent with
> what other ACPI architectures also pass to iommu_setup_dma_ops().
>
Ok, I'll add reason of changing it into commit log for everyone else.
>> Signed-off-by: Jianmin Lv <lvjianmin@...ngson.cn>
>> ---
>> drivers/acpi/arm64/dma.c | 44
>> +++++++++++++++++++++++++++++++++-----------
>> drivers/acpi/scan.c | 48
>> ++++++++++++++++++++++++------------------------
>> include/acpi/acpi_bus.h | 3 +--
>> include/linux/acpi.h | 7 +++----
>> 4 files changed, 61 insertions(+), 41 deletions(-)
>>
>> diff --git a/drivers/acpi/arm64/dma.c b/drivers/acpi/arm64/dma.c
>> index f16739a..64a41b2 100644
>> --- a/drivers/acpi/arm64/dma.c
>> +++ b/drivers/acpi/arm64/dma.c
>> @@ -4,11 +4,12 @@
>> #include <linux/device.h>
>> #include <linux/dma-direct.h>
>> -void acpi_arch_dma_setup(struct device *dev, u64 *dma_addr, u64
>> *dma_size)
>> +void acpi_arch_dma_setup(struct device *dev)
>> {
>> int ret;
>> u64 end, mask;
>> - u64 dmaaddr = 0, size = 0, offset = 0;
>> + u64 size = 0;
>> + const struct bus_dma_region *map = NULL;
>> /*
>> * If @dev is expected to be DMA-capable then the bus code that
>> created
>> @@ -26,7 +27,33 @@ void acpi_arch_dma_setup(struct device *dev, u64
>> *dma_addr, u64 *dma_size)
>> else
>> size = 1ULL << 32;
>> - ret = acpi_dma_get_range(dev, &dmaaddr, &offset, &size);
>> + ret = acpi_dma_get_range(dev, &map);
>> + if (!ret) {
>> + const struct bus_dma_region *r = map;
>> + u64 dma_start, dma_end = 0;
>> +
>> + /* determine the overall bounds of all dma regions */
>> + for (dma_start = U64_MAX; r->size; r++) {
>> +
>> + /* Take lower and upper limits */
>> + if (r->dma_start < dma_start)
>> + dma_start = r->dma_start;
>
> dma_start now only serves as an overcomplicated way to tell if the list
> was empty, so we don't need it...
Ok,thanks.
>
>> + if (r->dma_start + r->size - 1 > dma_end)
>> + dma_end = r->dma_start + r->size - 1;
>> + }
>> +
>> + if (dma_start >= dma_end) {
>> + dev_dbg(dev, "Invalid DMA regions configuration\n");
>> + return;
>
> ...but we also don't need this check anway - either there was at least
> one valid resource, so dma_end is now set to something sensible, or
> there were none, in which case the implementation of
> acpi_dma_get_range() here returns success while leaving map == NULL, so
> we've already crashed dereferencing r->size.
>
Ok, thanks.
>> + }
>> +
>> + mask = DMA_BIT_MASK(ilog2(dma_end) + 1);
>> + dev->bus_dma_limit = dma_end;
>> + dev->dma_range_map = map;
>> + dev->coherent_dma_mask = min(dev->coherent_dma_mask, mask);
>> + *dev->dma_mask = min(*dev->dma_mask, mask);
>
> Don't duplicate all this, just set "size = dma_end + 1" so the existing
> code below picks it up.
>
TBH, I'm not familiar with ARM64's DMA stuff, but from the code here, I
think there are two ways to get dma ranges: acpi_dma_get_range or
iort_dma_get_ranges.
Before the patch, after obtaining the dmaaddr, offset and size in any
way of the both, the bus_dma_limit, mask and dma_range_map will be
initialized, and dma_range_map is created a *new* one for *both* ways.
But after changing acpi_dma_get_range, when we are ok to obtain
dma_range_map by acpi_dma_get_range, we'll use it instead of creating a
new one like before. For iort_dma_get_ranges, we have to still create a
new dma_range_map. So, I have to handle separately each way here.
It seems that it's enough to handle dma_range_map separately, and others
can be still initialized in one place.
>> + }
>> +
>> if (ret == -ENODEV)
>> ret = iort_dma_get_ranges(dev, &size);
>> if (!ret) {
>> @@ -34,17 +61,12 @@ void acpi_arch_dma_setup(struct device *dev, u64
>> *dma_addr, u64 *dma_size)
>> * Limit coherent and dma mask based on size retrieved from
>> * firmware.
>> */
>> - end = dmaaddr + size - 1;
>> + end = size - 1;
>> mask = DMA_BIT_MASK(ilog2(end) + 1);
>> dev->bus_dma_limit = end;
>> dev->coherent_dma_mask = min(dev->coherent_dma_mask, mask);
>> *dev->dma_mask = min(*dev->dma_mask, mask);
>> - }
>> - *dma_addr = dmaaddr;
>> - *dma_size = size;
>> -
>> - ret = dma_direct_set_offset(dev, dmaaddr + offset, dmaaddr, size);
>> -
>> - dev_dbg(dev, "dma_offset(%#08llx)%s\n", offset, ret ? " failed!"
>> : "");
>> + ret = dma_direct_set_offset(dev, 0, 0, size);
>
> Don't call this - we're setting dev->dma_range_map now, so it will only
> scream and fail (or do nothing if there's no offset).
>
Same as above.
>> + }
>> }
>> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
>> index 762b61f..736517e 100644
>> --- a/drivers/acpi/scan.c
>> +++ b/drivers/acpi/scan.c
>> @@ -20,6 +20,7 @@
>> #include <linux/platform_data/x86/apple.h>
>> #include <linux/pgtable.h>
>> #include <linux/crc32.h>
>> +#include <linux/dma-direct.h>
>> #include "internal.h"
>> @@ -1492,15 +1493,15 @@ enum dev_dma_attr acpi_get_dma_attr(struct
>> acpi_device *adev)
>> *
>> * Return 0 on success, < 0 on failure.
>> */
>
> Don't forget to update the kerneldoc as well.
>
Ok, thanks.
>> -int acpi_dma_get_range(struct device *dev, u64 *dma_addr, u64 *offset,
>> - u64 *size)
>> +int acpi_dma_get_range(struct device *dev, const struct
>> bus_dma_region **map)
>> {
>> struct acpi_device *adev;
>> LIST_HEAD(list);
>> struct resource_entry *rentry;
>> int ret;
>> struct device *dma_dev = dev;
>> - u64 len, dma_start = U64_MAX, dma_end = 0, dma_offset = 0;
>> + int num_ranges = 0;
>> + struct bus_dma_region *r;
>> /*
>> * Walk the device tree chasing an ACPI companion with a _DMA
>> @@ -1525,31 +1526,31 @@ int acpi_dma_get_range(struct device *dev, u64
>> *dma_addr, u64 *offset,
>> ret = acpi_dev_get_dma_resources(adev, &list);
>> if (ret > 0) {
>> + list_for_each_entry(rentry, &list, node)
>> + num_ranges++;
>
> We already have the number of resources in ret.
>
Ok, thanks.
> Looking at this, I also now wonder if we're doing the right thing if the
> object is present but contains no resources. The spec isn't clear
> whether that's even really valid, but if it is, is it meaningful? It
> seems we'd currently consider an empty object equivalent to no object,
> but if anything it should perhaps be interpreted as the opposite, i.e.
> that no DMA is possible because the bus does not decode any ranges. Is
> anyone more familiar with the intent of the spec here?
>
> Thanks,
> Robin.
>
According to _DMA of ACPI spec, _DMA is optional, if without it(no _DMA
object configured in DSDT), kernel assumes that any address range placed
on bus by a child device is valid and can be decoded. So I think it is
still legal if _DMA is present and no resources contained in it. I mean
an empty _DMA object equals no _DMA object. But obviously it's not
meaningful for an empty _DMA object, anybody should not pass an empty
_DMA object.
>> +
>> + r = kcalloc(num_ranges + 1, sizeof(*r), GFP_KERNEL);
>> + if (!r) {
>> + ret = -ENOMEM;
>> + goto out;
>> + }
>> +
>> + *map = r;
>> +
>> list_for_each_entry(rentry, &list, node) {
>> - if (dma_offset && rentry->offset != dma_offset) {
>> + if (rentry->res->start >= rentry->res->end) {
>> ret = -EINVAL;
>> - dev_warn(dma_dev, "Can't handle multiple windows with
>> different offsets\n");
>> + dev_dbg(dma_dev, "Invalid DMA regions configuration\n");
>> goto out;
>> }
>> - dma_offset = rentry->offset;
>> -
>> - /* Take lower and upper limits */
>> - if (rentry->res->start < dma_start)
>> - dma_start = rentry->res->start;
>> - if (rentry->res->end > dma_end)
>> - dma_end = rentry->res->end;
>> - }
>> - if (dma_start >= dma_end) {
>> - ret = -EINVAL;
>> - dev_dbg(dma_dev, "Invalid DMA regions configuration\n");
>> - goto out;
>> + r->cpu_start = rentry->res->start;
>> + r->dma_start = rentry->res->start - rentry->offset;
>> + r->size = rentry->res->end - rentry->res->start + 1;
>> + r->offset = rentry->offset;
>> + r++;
>> }
>> - *dma_addr = dma_start - dma_offset;
>> - len = dma_end - dma_start;
>> - *size = max(len, len + 1);
>> - *offset = dma_offset;
>> }
>> out:
>> acpi_dev_free_resource_list(&list);
>> @@ -1639,20 +1640,19 @@ int acpi_dma_configure_id(struct device *dev,
>> enum dev_dma_attr attr,
>> const u32 *input_id)
>> {
>> const struct iommu_ops *iommu;
>> - u64 dma_addr = 0, size = 0;
>> if (attr == DEV_DMA_NOT_SUPPORTED) {
>> set_dma_ops(dev, &dma_dummy_ops);
>> return 0;
>> }
>> - acpi_arch_dma_setup(dev, &dma_addr, &size);
>> + acpi_arch_dma_setup(dev);
>> iommu = acpi_iommu_configure_id(dev, input_id);
>> if (PTR_ERR(iommu) == -EPROBE_DEFER)
>> return -EPROBE_DEFER;
>> - arch_setup_dma_ops(dev, dma_addr, size,
>> + arch_setup_dma_ops(dev, 0, U64_MAX,
>> iommu, attr == DEV_DMA_COHERENT);
>> return 0;
>> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
>> index 0dc1ea0b..e106073 100644
>> --- a/include/acpi/acpi_bus.h
>> +++ b/include/acpi/acpi_bus.h
>> @@ -611,8 +611,7 @@ struct acpi_pci_root {
>> int acpi_iommu_fwspec_init(struct device *dev, u32 id,
>> struct fwnode_handle *fwnode,
>> const struct iommu_ops *ops);
>> -int acpi_dma_get_range(struct device *dev, u64 *dma_addr, u64 *offset,
>> - u64 *size);
>> +int acpi_dma_get_range(struct device *dev, const struct
>> bus_dma_region **map);
>> int acpi_dma_configure_id(struct device *dev, enum dev_dma_attr attr,
>> const u32 *input_id);
>> static inline int acpi_dma_configure(struct device *dev,
>> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
>> index 44975c1..34e0545 100644
>> --- a/include/linux/acpi.h
>> +++ b/include/linux/acpi.h
>> @@ -280,12 +280,12 @@ int acpi_table_parse_madt(enum acpi_madt_type id,
>> #ifdef CONFIG_ARM64
>> void acpi_numa_gicc_affinity_init(struct acpi_srat_gicc_affinity *pa);
>> -void acpi_arch_dma_setup(struct device *dev, u64 *dma_addr, u64
>> *dma_size);
>> +void acpi_arch_dma_setup(struct device *dev);
>> #else
>> static inline void
>> acpi_numa_gicc_affinity_init(struct acpi_srat_gicc_affinity *pa) { }
>> static inline void
>> -acpi_arch_dma_setup(struct device *dev, u64 *dma_addr, u64 *dma_size)
>> { }
>> +acpi_arch_dma_setup(struct device *dev) { }
>> #endif
>> int acpi_numa_memory_affinity_init (struct acpi_srat_mem_affinity *ma);
>> @@ -974,8 +974,7 @@ static inline enum dev_dma_attr
>> acpi_get_dma_attr(struct acpi_device *adev)
>> return DEV_DMA_NOT_SUPPORTED;
>> }
>> -static inline int acpi_dma_get_range(struct device *dev, u64 *dma_addr,
>> - u64 *offset, u64 *size)
>> +static inline int acpi_dma_get_range(struct device *dev, const struct
>> bus_dma_region **map)
>> {
>> return -ENODEV;
>> }
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