2023-11-24 19:27:20

by Jan Kuliga

Subject: [PATCH v3 5/5] dmaengine: xilinx: xdma: Ease dma_pool alignment requirements

According to the XDMA datasheet (PG195), the address of any descriptor
must be 32 byte aligned. The datasheet also states that a contiguous
block of descriptors must not cross a 4k address boundary. Therefore,
it is possible to ease the pressure put on the dma_pool allocator
just by requiring sufficient alignment and boundary values. Add proper
macro definition and change the values passed into the
dma_pool_create().

Signed-off-by: Jan Kuliga <[email protected]>
---
drivers/dma/xilinx/xdma-regs.h | 7 ++++---
drivers/dma/xilinx/xdma.c | 6 +++---
2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/dma/xilinx/xdma-regs.h b/drivers/dma/xilinx/xdma-regs.h
index 6bf7ae84e452..d5cb12e6b8d4 100644
--- a/drivers/dma/xilinx/xdma-regs.h
+++ b/drivers/dma/xilinx/xdma-regs.h
@@ -64,9 +64,10 @@ struct xdma_hw_desc {
__le64 next_desc;
};

-#define XDMA_DESC_SIZE sizeof(struct xdma_hw_desc)
-#define XDMA_DESC_BLOCK_SIZE (XDMA_DESC_SIZE * XDMA_DESC_ADJACENT)
-#define XDMA_DESC_BLOCK_ALIGN 4096
+#define XDMA_DESC_SIZE sizeof(struct xdma_hw_desc)
+#define XDMA_DESC_BLOCK_SIZE (XDMA_DESC_SIZE * XDMA_DESC_ADJACENT)
+#define XDMA_DESC_BLOCK_ALIGN 32
+#define XDMA_DESC_BLOCK_BOUNDARY 4096

/*
* Channel registers
diff --git a/drivers/dma/xilinx/xdma.c b/drivers/dma/xilinx/xdma.c
index de4615bd4ee5..d32ae93e18b6 100644
--- a/drivers/dma/xilinx/xdma.c
+++ b/drivers/dma/xilinx/xdma.c
@@ -735,9 +735,9 @@ static int xdma_alloc_chan_resources(struct dma_chan *chan)
return -EINVAL;
}

- xdma_chan->desc_pool = dma_pool_create(dma_chan_name(chan),
- dev, XDMA_DESC_BLOCK_SIZE,
- XDMA_DESC_BLOCK_ALIGN, 0);
+ xdma_chan->desc_pool = dma_pool_create(dma_chan_name(chan), dev,
+ XDMA_DESC_BLOCK_SIZE, XDMA_DESC_BLOCK_ALIGN,
+ XDMA_DESC_BLOCK_BOUNDARY);
if (!xdma_chan->desc_pool) {
xdma_err(xdev, "unable to allocate descriptor pool");
return -ENOMEM;
--
2.34.1

2023-11-27 16:44:11

by Lizhi Hou

Subject: Re: [PATCH v3 5/5] dmaengine: xilinx: xdma: Ease dma_pool alignment requirements

On 11/24/23 11:25, Jan Kuliga wrote:
> According to the XDMA datasheet (PG195), the address of any descriptor
> must be 32 byte aligned. The datasheet also states that a contiguous
> block of descriptors must not cross a 4k address boundary. Therefore,
> it is possible to ease the pressure put on the dma_pool allocator
> just by requiring sufficient alignment and boundary values. Add proper
> macro definition and change the values passed into the
> dma_pool_create().
>
> Signed-off-by: Jan Kuliga <[email protected]>
> ---
> drivers/dma/xilinx/xdma-regs.h | 7 ++++---
> drivers/dma/xilinx/xdma.c | 6 +++---
> 2 files changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/dma/xilinx/xdma-regs.h b/drivers/dma/xilinx/xdma-regs.h
> index 6bf7ae84e452..d5cb12e6b8d4 100644
> --- a/drivers/dma/xilinx/xdma-regs.h
> +++ b/drivers/dma/xilinx/xdma-regs.h
> @@ -64,9 +64,10 @@ struct xdma_hw_desc {
> __le64 next_desc;
> };
>
> -#define XDMA_DESC_SIZE sizeof(struct xdma_hw_desc)
> -#define XDMA_DESC_BLOCK_SIZE (XDMA_DESC_SIZE * XDMA_DESC_ADJACENT)
> -#define XDMA_DESC_BLOCK_ALIGN 4096
> +#define XDMA_DESC_SIZE sizeof(struct xdma_hw_desc)
> +#define XDMA_DESC_BLOCK_SIZE (XDMA_DESC_SIZE * XDMA_DESC_ADJACENT)
> +#define XDMA_DESC_BLOCK_ALIGN 32
> +#define XDMA_DESC_BLOCK_BOUNDARY 4096
>
> /*
> * Channel registers
> diff --git a/drivers/dma/xilinx/xdma.c b/drivers/dma/xilinx/xdma.c
> index de4615bd4ee5..d32ae93e18b6 100644
> --- a/drivers/dma/xilinx/xdma.c
> +++ b/drivers/dma/xilinx/xdma.c
> @@ -735,9 +735,9 @@ static int xdma_alloc_chan_resources(struct dma_chan *chan)
> return -EINVAL;
> }
>
> - xdma_chan->desc_pool = dma_pool_create(dma_chan_name(chan),
> - dev, XDMA_DESC_BLOCK_SIZE,
> - XDMA_DESC_BLOCK_ALIGN, 0);
> + xdma_chan->desc_pool = dma_pool_create(dma_chan_name(chan), dev,
> + XDMA_DESC_BLOCK_SIZE, XDMA_DESC_BLOCK_ALIGN,
> + XDMA_DESC_BLOCK_BOUNDARY);
> if (!xdma_chan->desc_pool) {
> xdma_err(xdev, "unable to allocate descriptor pool");
> return -ENOMEM;

This is probably not needed. The 32 adjacent descriptors here is 1024
bytes. Defining 4k alignment should be good enough.

Thanks,

Lizhi

2023-11-27 16:51:58

by Lizhi Hou

Subject: Re: [PATCH v3 5/5] dmaengine: xilinx: xdma: Ease dma_pool alignment requirements

On 11/27/23 08:43, Lizhi Hou wrote:
>
> On 11/24/23 11:25, Jan Kuliga wrote:
>> According to the XDMA datasheet (PG195), the address of any descriptor
>> must be 32 byte aligned. The datasheet also states that a contiguous
>> block of descriptors must not cross a 4k address boundary. Therefore,
>> it is possible to ease the pressure put on the dma_pool allocator
>> just by requiring sufficient alignment and boundary values. Add proper
>> macro definition and change the values passed into the
>> dma_pool_create().
>>
>> Signed-off-by: Jan Kuliga <[email protected]>
>> ---
>>   drivers/dma/xilinx/xdma-regs.h | 7 ++++---
>>   drivers/dma/xilinx/xdma.c      | 6 +++---
>>   2 files changed, 7 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/dma/xilinx/xdma-regs.h
>> b/drivers/dma/xilinx/xdma-regs.h
>> index 6bf7ae84e452..d5cb12e6b8d4 100644
>> --- a/drivers/dma/xilinx/xdma-regs.h
>> +++ b/drivers/dma/xilinx/xdma-regs.h
>> @@ -64,9 +64,10 @@ struct xdma_hw_desc {
>>       __le64        next_desc;
>>   };
>>   -#define XDMA_DESC_SIZE        sizeof(struct xdma_hw_desc)
>> -#define XDMA_DESC_BLOCK_SIZE    (XDMA_DESC_SIZE * XDMA_DESC_ADJACENT)
>> -#define XDMA_DESC_BLOCK_ALIGN    4096
>> +#define XDMA_DESC_SIZE            sizeof(struct xdma_hw_desc)
>> +#define XDMA_DESC_BLOCK_SIZE        (XDMA_DESC_SIZE *
>> XDMA_DESC_ADJACENT)
>> +#define XDMA_DESC_BLOCK_ALIGN        32
>> +#define XDMA_DESC_BLOCK_BOUNDARY    4096
>>     /*
>>    * Channel registers
>> diff --git a/drivers/dma/xilinx/xdma.c b/drivers/dma/xilinx/xdma.c
>> index de4615bd4ee5..d32ae93e18b6 100644
>> --- a/drivers/dma/xilinx/xdma.c
>> +++ b/drivers/dma/xilinx/xdma.c
>> @@ -735,9 +735,9 @@ static int xdma_alloc_chan_resources(struct
>> dma_chan *chan)
>>           return -EINVAL;
>>       }
>>   -    xdma_chan->desc_pool = dma_pool_create(dma_chan_name(chan),
>> -                           dev, XDMA_DESC_BLOCK_SIZE,
>> -                           XDMA_DESC_BLOCK_ALIGN, 0);
>> +    xdma_chan->desc_pool = dma_pool_create(dma_chan_name(chan), dev,
>> +                XDMA_DESC_BLOCK_SIZE, XDMA_DESC_BLOCK_ALIGN,
>> +                        XDMA_DESC_BLOCK_BOUNDARY);
>>       if (!xdma_chan->desc_pool) {
>>           xdma_err(xdev, "unable to allocate descriptor pool");
>>           return -ENOMEM;
>
> This is probably not needed. The 32 adjacent descriptors here is 1024
> bytes. Defining 4k alignment should be good enough.
Oh, Just noticed the you have changed the alignment to 32. Sorry, I just
hit send too quick.
>
> Thanks,
>
> Lizhi
>
>