Some platforms do have DMA, but DMA there is always direct and coherent.
Currently, even on such platforms DMA sync operations are compiled and
called.
Add a new hidden Kconfig symbol, DMA_NEED_SYNC, and set it only when
either sync operations are needed or there is DMA ops or swiotlb
enabled. Set dma_need_sync() and dma_skip_sync() depending on this
symbol state and don't call sync ops when dma_skip_sync() is true.
The change allows for future optimizations of DMA sync calls depending
on compile-time or runtime conditions.
Signed-off-by: Alexander Lobakin <[email protected]>
---
kernel/dma/Kconfig | 4 ++
include/linux/dma-mapping.h | 80 +++++++++++++++++++++++++++++++------
kernel/dma/mapping.c | 20 +++++-----
3 files changed, 81 insertions(+), 23 deletions(-)
diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
index d62f5957f36b..1c9ff05b1ecb 100644
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -107,6 +107,10 @@ config DMA_BOUNCE_UNALIGNED_KMALLOC
bool
depends on SWIOTLB
+config DMA_NEED_SYNC
+ def_bool ARCH_HAS_SYNC_DMA_FOR_DEVICE || ARCH_HAS_SYNC_DMA_FOR_CPU || \
+ ARCH_HAS_SYNC_DMA_FOR_CPU_ALL || DMA_OPS || SWIOTLB
+
config DMA_RESTRICTED_POOL
bool "DMA Restricted Pool"
depends on OF && OF_RESERVED_MEM && SWIOTLB
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 4a658de44ee9..6c7640441214 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -117,13 +117,13 @@ dma_addr_t dma_map_resource(struct device *dev, phys_addr_t phys_addr,
size_t size, enum dma_data_direction dir, unsigned long attrs);
void dma_unmap_resource(struct device *dev, dma_addr_t addr, size_t size,
enum dma_data_direction dir, unsigned long attrs);
-void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, size_t size,
+void __dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, size_t size,
enum dma_data_direction dir);
-void dma_sync_single_for_device(struct device *dev, dma_addr_t addr,
+void __dma_sync_single_for_device(struct device *dev, dma_addr_t addr,
size_t size, enum dma_data_direction dir);
-void dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
+void __dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
int nelems, enum dma_data_direction dir);
-void dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
+void __dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
int nelems, enum dma_data_direction dir);
void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
gfp_t flag, unsigned long attrs);
@@ -147,7 +147,7 @@ u64 dma_get_required_mask(struct device *dev);
bool dma_addressing_limited(struct device *dev);
size_t dma_max_mapping_size(struct device *dev);
size_t dma_opt_mapping_size(struct device *dev);
-bool dma_need_sync(struct device *dev, dma_addr_t dma_addr);
+bool __dma_need_sync(struct device *dev, dma_addr_t dma_addr);
unsigned long dma_get_merge_boundary(struct device *dev);
struct sg_table *dma_alloc_noncontiguous(struct device *dev, size_t size,
enum dma_data_direction dir, gfp_t gfp, unsigned long attrs);
@@ -195,19 +195,19 @@ static inline void dma_unmap_resource(struct device *dev, dma_addr_t addr,
size_t size, enum dma_data_direction dir, unsigned long attrs)
{
}
-static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
- size_t size, enum dma_data_direction dir)
+static inline void __dma_sync_single_for_cpu(struct device *dev,
+ dma_addr_t addr, size_t size, enum dma_data_direction dir)
{
}
-static inline void dma_sync_single_for_device(struct device *dev,
+static inline void __dma_sync_single_for_device(struct device *dev,
dma_addr_t addr, size_t size, enum dma_data_direction dir)
{
}
-static inline void dma_sync_sg_for_cpu(struct device *dev,
+static inline void __dma_sync_sg_for_cpu(struct device *dev,
struct scatterlist *sg, int nelems, enum dma_data_direction dir)
{
}
-static inline void dma_sync_sg_for_device(struct device *dev,
+static inline void __dma_sync_sg_for_device(struct device *dev,
struct scatterlist *sg, int nelems, enum dma_data_direction dir)
{
}
@@ -277,7 +277,7 @@ static inline size_t dma_opt_mapping_size(struct device *dev)
{
return 0;
}
-static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr)
+static inline bool __dma_need_sync(struct device *dev, dma_addr_t dma_addr)
{
return false;
}
@@ -348,18 +348,72 @@ static inline void dma_unmap_single_attrs(struct device *dev, dma_addr_t addr,
return dma_unmap_page_attrs(dev, addr, size, dir, attrs);
}
+static inline void __dma_sync_single_range_for_cpu(struct device *dev,
+ dma_addr_t addr, unsigned long offset, size_t size,
+ enum dma_data_direction dir)
+{
+ __dma_sync_single_for_cpu(dev, addr + offset, size, dir);
+}
+
+static inline void __dma_sync_single_range_for_device(struct device *dev,
+ dma_addr_t addr, unsigned long offset, size_t size,
+ enum dma_data_direction dir)
+{
+ __dma_sync_single_for_device(dev, addr + offset, size, dir);
+}
+
+static inline bool dma_skip_sync(const struct device *dev)
+{
+ return !IS_ENABLED(CONFIG_DMA_NEED_SYNC);
+}
+
+static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr)
+{
+ return !dma_skip_sync(dev) ? __dma_need_sync(dev, dma_addr) : false;
+}
+
+static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
+ size_t size, enum dma_data_direction dir)
+{
+ if (!dma_skip_sync(dev))
+ __dma_sync_single_for_cpu(dev, addr, size, dir);
+}
+
+static inline void dma_sync_single_for_device(struct device *dev,
+ dma_addr_t addr, size_t size, enum dma_data_direction dir)
+{
+ if (!dma_skip_sync(dev))
+ __dma_sync_single_for_device(dev, addr, size, dir);
+}
+
+static inline void dma_sync_sg_for_cpu(struct device *dev,
+ struct scatterlist *sg, int nelems, enum dma_data_direction dir)
+{
+ if (!dma_skip_sync(dev))
+ __dma_sync_sg_for_cpu(dev, sg, nelems, dir);
+}
+
+static inline void dma_sync_sg_for_device(struct device *dev,
+ struct scatterlist *sg, int nelems, enum dma_data_direction dir)
+{
+ if (!dma_skip_sync(dev))
+ __dma_sync_sg_for_device(dev, sg, nelems, dir);
+}
+
static inline void dma_sync_single_range_for_cpu(struct device *dev,
dma_addr_t addr, unsigned long offset, size_t size,
enum dma_data_direction dir)
{
- return dma_sync_single_for_cpu(dev, addr + offset, size, dir);
+ if (!dma_skip_sync(dev))
+ __dma_sync_single_for_cpu(dev, addr + offset, size, dir);
}
static inline void dma_sync_single_range_for_device(struct device *dev,
dma_addr_t addr, unsigned long offset, size_t size,
enum dma_data_direction dir)
{
- return dma_sync_single_for_device(dev, addr + offset, size, dir);
+ if (!dma_skip_sync(dev))
+ __dma_sync_single_for_device(dev, addr + offset, size, dir);
}
/**
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 58db8fd70471..85feaa0e008c 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -329,7 +329,7 @@ void dma_unmap_resource(struct device *dev, dma_addr_t addr, size_t size,
}
EXPORT_SYMBOL(dma_unmap_resource);
-void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, size_t size,
+void __dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, size_t size,
enum dma_data_direction dir)
{
const struct dma_map_ops *ops = get_dma_ops(dev);
@@ -341,9 +341,9 @@ void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, size_t size,
ops->sync_single_for_cpu(dev, addr, size, dir);
debug_dma_sync_single_for_cpu(dev, addr, size, dir);
}
-EXPORT_SYMBOL(dma_sync_single_for_cpu);
+EXPORT_SYMBOL(__dma_sync_single_for_cpu);
-void dma_sync_single_for_device(struct device *dev, dma_addr_t addr,
+void __dma_sync_single_for_device(struct device *dev, dma_addr_t addr,
size_t size, enum dma_data_direction dir)
{
const struct dma_map_ops *ops = get_dma_ops(dev);
@@ -355,9 +355,9 @@ void dma_sync_single_for_device(struct device *dev, dma_addr_t addr,
ops->sync_single_for_device(dev, addr, size, dir);
debug_dma_sync_single_for_device(dev, addr, size, dir);
}
-EXPORT_SYMBOL(dma_sync_single_for_device);
+EXPORT_SYMBOL(__dma_sync_single_for_device);
-void dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
+void __dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
int nelems, enum dma_data_direction dir)
{
const struct dma_map_ops *ops = get_dma_ops(dev);
@@ -369,9 +369,9 @@ void dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
ops->sync_sg_for_cpu(dev, sg, nelems, dir);
debug_dma_sync_sg_for_cpu(dev, sg, nelems, dir);
}
-EXPORT_SYMBOL(dma_sync_sg_for_cpu);
+EXPORT_SYMBOL(__dma_sync_sg_for_cpu);
-void dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
+void __dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
int nelems, enum dma_data_direction dir)
{
const struct dma_map_ops *ops = get_dma_ops(dev);
@@ -383,7 +383,7 @@ void dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
ops->sync_sg_for_device(dev, sg, nelems, dir);
debug_dma_sync_sg_for_device(dev, sg, nelems, dir);
}
-EXPORT_SYMBOL(dma_sync_sg_for_device);
+EXPORT_SYMBOL(__dma_sync_sg_for_device);
/*
* The whole dma_get_sgtable() idea is fundamentally unsafe - it seems
@@ -841,7 +841,7 @@ size_t dma_opt_mapping_size(struct device *dev)
}
EXPORT_SYMBOL_GPL(dma_opt_mapping_size);
-bool dma_need_sync(struct device *dev, dma_addr_t dma_addr)
+bool __dma_need_sync(struct device *dev, dma_addr_t dma_addr)
{
const struct dma_map_ops *ops = get_dma_ops(dev);
@@ -849,7 +849,7 @@ bool dma_need_sync(struct device *dev, dma_addr_t dma_addr)
return dma_direct_need_sync(dev, dma_addr);
return ops->sync_single_for_cpu || ops->sync_single_for_device;
}
-EXPORT_SYMBOL_GPL(dma_need_sync);
+EXPORT_SYMBOL_GPL(__dma_need_sync);
unsigned long dma_get_merge_boundary(struct device *dev)
{
--
2.43.0
On 2024-02-14 4:21 pm, Alexander Lobakin wrote:
> Some platforms do have DMA, but DMA there is always direct and coherent.
> Currently, even on such platforms DMA sync operations are compiled and
> called.
> Add a new hidden Kconfig symbol, DMA_NEED_SYNC, and set it only when
> either sync operations are needed or there is DMA ops or swiotlb
> enabled. Set dma_need_sync() and dma_skip_sync() depending on this
> symbol state and don't call sync ops when dma_skip_sync() is true.
> The change allows for future optimizations of DMA sync calls depending
> on compile-time or runtime conditions.
>
> Signed-off-by: Alexander Lobakin <[email protected]>
> ---
> kernel/dma/Kconfig | 4 ++
> include/linux/dma-mapping.h | 80 +++++++++++++++++++++++++++++++------
> kernel/dma/mapping.c | 20 +++++-----
> 3 files changed, 81 insertions(+), 23 deletions(-)
>
> diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
> index d62f5957f36b..1c9ff05b1ecb 100644
> --- a/kernel/dma/Kconfig
> +++ b/kernel/dma/Kconfig
> @@ -107,6 +107,10 @@ config DMA_BOUNCE_UNALIGNED_KMALLOC
> bool
> depends on SWIOTLB
>
> +config DMA_NEED_SYNC
> + def_bool ARCH_HAS_SYNC_DMA_FOR_DEVICE || ARCH_HAS_SYNC_DMA_FOR_CPU || \
> + ARCH_HAS_SYNC_DMA_FOR_CPU_ALL || DMA_OPS || SWIOTLB
I'm not sure DMA_OPS belongs here - several architectures have
non-trivial ops without syncs, e.g. Alpha.
> +
> config DMA_RESTRICTED_POOL
> bool "DMA Restricted Pool"
> depends on OF && OF_RESERVED_MEM && SWIOTLB
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index 4a658de44ee9..6c7640441214 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -117,13 +117,13 @@ dma_addr_t dma_map_resource(struct device *dev, phys_addr_t phys_addr,
> size_t size, enum dma_data_direction dir, unsigned long attrs);
> void dma_unmap_resource(struct device *dev, dma_addr_t addr, size_t size,
> enum dma_data_direction dir, unsigned long attrs);
> -void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, size_t size,
> +void __dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, size_t size,
> enum dma_data_direction dir);
> -void dma_sync_single_for_device(struct device *dev, dma_addr_t addr,
> +void __dma_sync_single_for_device(struct device *dev, dma_addr_t addr,
> size_t size, enum dma_data_direction dir);
> -void dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
> +void __dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
> int nelems, enum dma_data_direction dir);
> -void dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
> +void __dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
> int nelems, enum dma_data_direction dir);
> void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
> gfp_t flag, unsigned long attrs);
> @@ -147,7 +147,7 @@ u64 dma_get_required_mask(struct device *dev);
> bool dma_addressing_limited(struct device *dev);
> size_t dma_max_mapping_size(struct device *dev);
> size_t dma_opt_mapping_size(struct device *dev);
> -bool dma_need_sync(struct device *dev, dma_addr_t dma_addr);
> +bool __dma_need_sync(struct device *dev, dma_addr_t dma_addr);
> unsigned long dma_get_merge_boundary(struct device *dev);
> struct sg_table *dma_alloc_noncontiguous(struct device *dev, size_t size,
> enum dma_data_direction dir, gfp_t gfp, unsigned long attrs);
> @@ -195,19 +195,19 @@ static inline void dma_unmap_resource(struct device *dev, dma_addr_t addr,
> size_t size, enum dma_data_direction dir, unsigned long attrs)
> {
> }
> -static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
> - size_t size, enum dma_data_direction dir)
> +static inline void __dma_sync_single_for_cpu(struct device *dev,
> + dma_addr_t addr, size_t size, enum dma_data_direction dir)
To me it would feel more logical to put all the wrappers inside the
#ifdef CONFIG_HAS_DMA and not touch these stubs at all (what does it
mean to skip an inline no-op?). Or in fact, if dma_skip_sync() is
constant false for !HAS_DMA, then we could also just make the external
function declarations unconditional and remove the stubs. Not a critical
matter though, and I defer to whatever Christoph thinks is most
maintainable.
> {
> }
> -static inline void dma_sync_single_for_device(struct device *dev,
> +static inline void __dma_sync_single_for_device(struct device *dev,
> dma_addr_t addr, size_t size, enum dma_data_direction dir)
> {
> }
> -static inline void dma_sync_sg_for_cpu(struct device *dev,
> +static inline void __dma_sync_sg_for_cpu(struct device *dev,
> struct scatterlist *sg, int nelems, enum dma_data_direction dir)
> {
> }
> -static inline void dma_sync_sg_for_device(struct device *dev,
> +static inline void __dma_sync_sg_for_device(struct device *dev,
> struct scatterlist *sg, int nelems, enum dma_data_direction dir)
> {
> }
> @@ -277,7 +277,7 @@ static inline size_t dma_opt_mapping_size(struct device *dev)
> {
> return 0;
> }
> -static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr)
> +static inline bool __dma_need_sync(struct device *dev, dma_addr_t dma_addr)
> {
> return false;
> }
> @@ -348,18 +348,72 @@ static inline void dma_unmap_single_attrs(struct device *dev, dma_addr_t addr,
> return dma_unmap_page_attrs(dev, addr, size, dir, attrs);
> }
>
> +static inline void __dma_sync_single_range_for_cpu(struct device *dev,
> + dma_addr_t addr, unsigned long offset, size_t size,
> + enum dma_data_direction dir)
> +{
> + __dma_sync_single_for_cpu(dev, addr + offset, size, dir);
> +}
> +
> +static inline void __dma_sync_single_range_for_device(struct device *dev,
> + dma_addr_t addr, unsigned long offset, size_t size,
> + enum dma_data_direction dir)
> +{
> + __dma_sync_single_for_device(dev, addr + offset, size, dir);
> +}
There is no need to introduce these two.
> +
> +static inline bool dma_skip_sync(const struct device *dev)
> +{
> + return !IS_ENABLED(CONFIG_DMA_NEED_SYNC);
> +}
> +
> +static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr)
> +{
> + return !dma_skip_sync(dev) ? __dma_need_sync(dev, dma_addr) : false;
> +}
That's a bit of a mind-bender... is it actually just
return !dma_skip_sync(dev) && __dma_need_sync(dev, dma_addr);
?
(I do still think the negative flag makes it all a little harder to
follow in general than a positive "device needs to consider syncs" flag
would.)
> +static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
> + size_t size, enum dma_data_direction dir)
> +{
> + if (!dma_skip_sync(dev))
> + __dma_sync_single_for_cpu(dev, addr, size, dir);
> +}
> +
> +static inline void dma_sync_single_for_device(struct device *dev,
> + dma_addr_t addr, size_t size, enum dma_data_direction dir)
> +{
> + if (!dma_skip_sync(dev))
> + __dma_sync_single_for_device(dev, addr, size, dir);
> +}
> +
> +static inline void dma_sync_sg_for_cpu(struct device *dev,
> + struct scatterlist *sg, int nelems, enum dma_data_direction dir)
> +{
> + if (!dma_skip_sync(dev))
> + __dma_sync_sg_for_cpu(dev, sg, nelems, dir);
> +}
> +
> +static inline void dma_sync_sg_for_device(struct device *dev,
> + struct scatterlist *sg, int nelems, enum dma_data_direction dir)
> +{
> + if (!dma_skip_sync(dev))
> + __dma_sync_sg_for_device(dev, sg, nelems, dir);
> +}
> +
> static inline void dma_sync_single_range_for_cpu(struct device *dev,
> dma_addr_t addr, unsigned long offset, size_t size,
> enum dma_data_direction dir)
> {
> - return dma_sync_single_for_cpu(dev, addr + offset, size, dir);
> + if (!dma_skip_sync(dev))
> + __dma_sync_single_for_cpu(dev, addr + offset, size, dir);
> }
>
> static inline void dma_sync_single_range_for_device(struct device *dev,
> dma_addr_t addr, unsigned long offset, size_t size,
> enum dma_data_direction dir)
> {
> - return dma_sync_single_for_device(dev, addr + offset, size, dir);
> + if (!dma_skip_sync(dev))
> + __dma_sync_single_for_device(dev, addr + offset, size, dir);
> }
These two don't need changing either, since the dma_sync_single_*
wrappers have already taken care of it.
Thanks,
Robin.
On 2024-02-14 4:21 pm, Alexander Lobakin wrote:
[...]
> +static inline bool dma_skip_sync(const struct device *dev)
> +{
> + return !IS_ENABLED(CONFIG_DMA_NEED_SYNC);
> +}
One more thing, could we please also make this conditional on
!CONFIG_DMA_API_DEBUG so that that doesn't lose coverage for validating
syncs?
Thanks,
Robin.
On Wed, Feb 14, 2024 at 06:09:08PM +0000, Robin Murphy wrote:
> On 2024-02-14 4:21 pm, Alexander Lobakin wrote:
> [...]
>> +static inline bool dma_skip_sync(const struct device *dev)
>> +{
>> + return !IS_ENABLED(CONFIG_DMA_NEED_SYNC);
>> +}
>
> One more thing, could we please also make this conditional on
> !CONFIG_DMA_API_DEBUG so that that doesn't lose coverage for validating
> syncs?
Agreed.
On Wed, Feb 14, 2024 at 05:20:50PM +0000, Robin Murphy wrote:
>> +config DMA_NEED_SYNC
>> + def_bool ARCH_HAS_SYNC_DMA_FOR_DEVICE || ARCH_HAS_SYNC_DMA_FOR_CPU || \
>> + ARCH_HAS_SYNC_DMA_FOR_CPU_ALL || DMA_OPS || SWIOTLB
>
> I'm not sure DMA_OPS belongs here - several architectures have non-trivial
> ops without syncs, e.g. Alpha.
True, but peeking through the ops is a bit hard. And I don't think it's
worth optimizing the dma sync performance on Alpha :)
>> +static inline void __dma_sync_single_for_cpu(struct device *dev,
>> + dma_addr_t addr, size_t size, enum dma_data_direction dir)
>
> To me it would feel more logical to put all the wrappers inside the #ifdef
> CONFIG_HAS_DMA and not touch these stubs at all (what does it mean to skip
> an inline no-op?). Or in fact, if dma_skip_sync() is constant false for
> !HAS_DMA, then we could also just make the external function declarations
> unconditional and remove the stubs. Not a critical matter though, and I
> defer to whatever Christoph thinks is most maintainable.
Your idea sounds reasonable to me, but I don't have a strong preference.
>> +static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr)
>> +{
>> + return !dma_skip_sync(dev) ? __dma_need_sync(dev, dma_addr) : false;
>> +}
>
> That's a bit of a mind-bender... is it actually just
>
> return !dma_skip_sync(dev) && __dma_need_sync(dev, dma_addr);
>
> ?
That looks a lot more readable for sure.
> (I do still think the negative flag makes it all a little harder to follow
> in general than a positive "device needs to consider syncs" flag would.)
Probably.
From: Robin Murphy <[email protected]>
Date: Wed, 14 Feb 2024 17:20:50 +0000
> On 2024-02-14 4:21 pm, Alexander Lobakin wrote:
[...]
>> -static inline void dma_sync_single_for_cpu(struct device *dev,
>> dma_addr_t addr,
>> - size_t size, enum dma_data_direction dir)
>> +static inline void __dma_sync_single_for_cpu(struct device *dev,
>> + dma_addr_t addr, size_t size, enum dma_data_direction dir)
>
> To me it would feel more logical to put all the wrappers inside the
> #ifdef CONFIG_HAS_DMA and not touch these stubs at all (what does it
> mean to skip an inline no-op?). Or in fact, if dma_skip_sync() is
> constant false for !HAS_DMA, then we could also just make the external
> function declarations unconditional and remove the stubs. Not a critical
> matter though, and I defer to whatever Christoph thinks is most
> maintainable.
It's done like that due to that I'm adding a runtime check in the second
patch. I don't feel like touching this twice makes sense.
[...]
>> @@ -348,18 +348,72 @@ static inline void dma_unmap_single_attrs(struct
>> device *dev, dma_addr_t addr,
>> return dma_unmap_page_attrs(dev, addr, size, dir, attrs);
>> }
>> +static inline void __dma_sync_single_range_for_cpu(struct device *dev,
>> + dma_addr_t addr, unsigned long offset, size_t size,
>> + enum dma_data_direction dir)
>> +{
>> + __dma_sync_single_for_cpu(dev, addr + offset, size, dir);
>> +}
>> +
>> +static inline void __dma_sync_single_range_for_device(struct device
>> *dev,
>> + dma_addr_t addr, unsigned long offset, size_t size,
>> + enum dma_data_direction dir)
>> +{
>> + __dma_sync_single_for_device(dev, addr + offset, size, dir);
>> +}
>
> There is no need to introduce these two.
I already replied to this in the previous thread. Some subsys may want
to check for the shortcut earlier to avoid call ladders of their own
functions. See patch 6 for example where I use this one.
>
>> +
>> +static inline bool dma_skip_sync(const struct device *dev)
>> +{
>> + return !IS_ENABLED(CONFIG_DMA_NEED_SYNC);
>> +}
>> +
>> +static inline bool dma_need_sync(struct device *dev, dma_addr_t
>> dma_addr)
>> +{
>> + return !dma_skip_sync(dev) ? __dma_need_sync(dev, dma_addr) : false;
>> +}
>
> That's a bit of a mind-bender... is it actually just
>
> return !dma_skip_sync(dev) && __dma_need_sync(dev, dma_addr);
Oh, indeed ._.
>
> ?
>
> (I do still think the negative flag makes it all a little harder to
> follow in general than a positive "device needs to consider syncs" flag
> would.)
I think it was in the original Eric's idea and I kept this.
I'm fine with inverting it.
[...]
> Thanks,
> Robin.
Thanks,
Olek
On 19/02/2024 12:53 pm, Alexander Lobakin wrote:
> From: Robin Murphy <[email protected]>
> Date: Wed, 14 Feb 2024 17:20:50 +0000
>
>> On 2024-02-14 4:21 pm, Alexander Lobakin wrote:
>
> [...]
>
>>> -static inline void dma_sync_single_for_cpu(struct device *dev,
>>> dma_addr_t addr,
>>> - size_t size, enum dma_data_direction dir)
>>> +static inline void __dma_sync_single_for_cpu(struct device *dev,
>>> + dma_addr_t addr, size_t size, enum dma_data_direction dir)
>>
>> To me it would feel more logical to put all the wrappers inside the
>> #ifdef CONFIG_HAS_DMA and not touch these stubs at all (what does it
>> mean to skip an inline no-op?). Or in fact, if dma_skip_sync() is
>> constant false for !HAS_DMA, then we could also just make the external
>> function declarations unconditional and remove the stubs. Not a critical
>> matter though, and I defer to whatever Christoph thinks is most
>> maintainable.
>
> It's done like that due to that I'm adding a runtime check in the second
> patch. I don't feel like touching this twice makes sense.
Huh? Why would anything need touching twice? All I'm saying is that it's
pretty pointless to add any invocations of dma_skip_sync() in !HAS_DMA
paths where we already know the whole API is stubbed out anyway. The
only cases which are worth differentiating here are HAS_DMA +
DMA_NEED_SYNC vs. HAS_DMA + !DMA_NEED_SYNC (with the subsequent runtime
check then just subdividing the former).
>
> [...]
>
>>> @@ -348,18 +348,72 @@ static inline void dma_unmap_single_attrs(struct
>>> device *dev, dma_addr_t addr,
>>> return dma_unmap_page_attrs(dev, addr, size, dir, attrs);
>>> }
>>> +static inline void __dma_sync_single_range_for_cpu(struct device *dev,
>>> + dma_addr_t addr, unsigned long offset, size_t size,
>>> + enum dma_data_direction dir)
>>> +{
>>> + __dma_sync_single_for_cpu(dev, addr + offset, size, dir);
>>> +}
>>> +
>>> +static inline void __dma_sync_single_range_for_device(struct device
>>> *dev,
>>> + dma_addr_t addr, unsigned long offset, size_t size,
>>> + enum dma_data_direction dir)
>>> +{
>>> + __dma_sync_single_for_device(dev, addr + offset, size, dir);
>>> +}
>>
>> There is no need to introduce these two.
>
> I already replied to this in the previous thread. Some subsys may want
> to check for the shortcut earlier to avoid call ladders of their own
> functions. See patch 6 for example where I use this one.
Ugh, no. If the page pool code wants to be clever poking around and
sidestepping parts of the documented API, it can flippin' well open-code
a single addition to call __dma_sync_single_for_device() directly
itself. I'm not at all keen on having to maintain "common" APIs for such
niche trickery.
Thanks,
Robin.