[PATCH] cxgb4vf: remove obsolete DECLARE_PCI_UNMAP_ADDR usage

[PATCH] cxgb4vf: remove obsolete DECLARE_PCI_UNMAP_ADDR usage

[FUJITA Tomonori]

We could use DEFINE_DMA_UNMAP_ADDR instead but using
CONFIG_NEED_DMA_MAP_STATE is a simpler way to see if a platform does
real DMA unmapping.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
---
 drivers/net/cxgb4vf/sge.c |   14 +++++---------
 1 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/net/cxgb4vf/sge.c b/drivers/net/cxgb4vf/sge.c
index 3a7c02f..4bc1858 100644
--- a/drivers/net/cxgb4vf/sge.c
+++ b/drivers/net/cxgb4vf/sge.c
@@ -228,15 +228,11 @@ static inline bool is_buf_mapped(const struct rx_sw_desc *sdesc)
  */
 static inline int need_skb_unmap(void)
 {
-	/*
-	 * This structure is used to tell if the platfrom needs buffer
-	 * unmapping by checking if DECLARE_PCI_UNMAP_ADDR defines anything.
-	 */
-	struct dummy {
-		DECLARE_PCI_UNMAP_ADDR(addr);
-	};
-
-	return sizeof(struct dummy) != 0;
+#ifdef CONFIG_NEED_DMA_MAP_STATE
+	return 1;
+#else
+	return 0;
+#endif
 }
 
 /**
-- 
1.6.5

Re: [PATCH] cxgb4vf: remove obsolete DECLARE_PCI_UNMAP_ADDR usage

[FUJITA Tomonori]

On Thu, 8 Jul 2010 18:52:37 +0900
FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:

> We could use DEFINE_DMA_UNMAP_ADDR instead but using
> CONFIG_NEED_DMA_MAP_STATE is a simpler way to see if a platform does
> real DMA unmapping.
> 
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> ---
>  drivers/net/cxgb4vf/sge.c |   14 +++++---------
>  1 files changed, 5 insertions(+), 9 deletions(-)

btw, I'm not sure that seeing if a platform does real DMA unmapping in
a driver is a good thing. But I suppose that we need to accept it if
this leads to big performance boost.

Both can be applied to net-next.

Re: [PATCH] cxgb4vf: remove obsolete DECLARE_PCI_UNMAP_ADDR usage

[David Miller]

From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Date: Thu, 8 Jul 2010 18:52:37 +0900

> We could use DEFINE_DMA_UNMAP_ADDR instead but using
> CONFIG_NEED_DMA_MAP_STATE is a simpler way to see if a platform does
> real DMA unmapping.
> 
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

Applied.

Re: [PATCH] cxgb4vf: remove obsolete DECLARE_PCI_UNMAP_ADDR usage

[David Miller]

From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Date: Thu, 08 Jul 2010 19:01:26 +0900

> On Thu, 8 Jul 2010 18:52:37 +0900
> FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
> 
>> We could use DEFINE_DMA_UNMAP_ADDR instead but using
>> CONFIG_NEED_DMA_MAP_STATE is a simpler way to see if a platform does
>> real DMA unmapping.
>> 
>> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
>> ---
>>  drivers/net/cxgb4vf/sge.c |   14 +++++---------
>>  1 files changed, 5 insertions(+), 9 deletions(-)
> 
> btw, I'm not sure that seeing if a platform does real DMA unmapping in
> a driver is a good thing. But I suppose that we need to accept it if
> this leads to big performance boost.
> 
> Both can be applied to net-next.

I think the value of these "optimizations" is rapidly decreasing to
zero.  And I believe I've told the authors of either this driver or
another one that they should just remove this stuff completely.

Re: [PATCH] cxgb4vf: remove obsolete DECLARE_PCI_UNMAP_ADDR usage

[FUJITA Tomonori]

On Thu, 08 Jul 2010 23:09:39 -0700 (PDT)
David Miller <davem@davemloft.net> wrote:

> > btw, I'm not sure that seeing if a platform does real DMA unmapping in
> > a driver is a good thing. But I suppose that we need to accept it if
> > this leads to big performance boost.
> > 
> > Both can be applied to net-next.
> 
> I think the value of these "optimizations" is rapidly decreasing to
> zero.  And I believe I've told the authors of either this driver or
> another one that they should just remove this stuff completely.

I prefer to remove this stuff completely too.

If this trick improves the performance greatly, we could add this to
the DMA API (that's better than adding such ifdef hack to drivers).