Re: [PATCH] powerpc: dma-mapping: Return dma_direct_ops variable when dev == NULL

[Chunhe Lan]

On 01/14/2014 06:14 PM, Benjamin Herrenschmidt wrote:
On Tue, 2014-01-14 at 17:44 +0800, Chunhe Lan wrote:
Without this patch, kind of below error will be dumped if
'insmod ixgbevf.ko' is executed:
     ixgbevf: Intel(R) 10 Gigabit PCI Express Virtual Function
              Network Driver - version 2.7.12-k
     ixgbevf: Copyright (c) 2009 - 2012 Intel Corporation.
     ixgbevf 0000:01:10.0: enabling device (0000 -> 0002)
     ixgbevf 0000:01:10.0: No usable DMA configuration, aborting
     ixgbevf: probe of 0000:01:10.0 failed with error -5
     ......
     ......
That's not right. The DMA ops must be set properly for the VF somewhere
in the arch code instead. When creating VFs, is there a hook allowing
the arch to fix things up ?

(Also adding linux-pci on CC)

Ben.

Signed-off-by: Chunhe Lan <chunhe....@freescale.com>
Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Tested-by: Chunhe Lan <chunhe....@freescale.com>
---
  arch/powerpc/include/asm/dma-mapping.h |   13 +++++++++----
  1 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/dma-mapping.h 
b/arch/powerpc/include/asm/dma-mapping.h
index e27e9ad..b8c10de 100644
--- a/arch/powerpc/include/asm/dma-mapping.h
+++ b/arch/powerpc/include/asm/dma-mapping.h
@@ -84,10 +84,15 @@ static inline struct dma_map_ops *get_dma_ops(struct device 
*dev)
        I see the get_dma_ops function in 
arch/*x86*/include/asm/dma-mapping.h as the following:

 32 static inline struct dma_map_ops *get_dma_ops(struct device *dev)
 33 {
 34 #ifndef CONFIG_X86_DEV_DMA_OPS
 35         return dma_ops;
 36 #else
 37         if (unlikely(!dev) || !dev->archdata.dma_ops)
 38                 return dma_ops;
 39         else
 40                 return dev->archdata.dma_ops;
 41 #endif
 42 }

        And also  see the get_dma_ops function in 
arch/*arm*/include/asm/dma-mapping.h as the following:

 18 static inline struct dma_map_ops *get_dma_ops(struct device *dev)
 19 {
 20         if (dev && dev->archdata.dma_ops)
 21                 return dev->archdata.dma_ops;
 22         return &arm_dma_ops;
 23 }

      Why not powerpc use this method to process dev == NULL ?

Thanks,
-Chunhe

         * only ISA DMA device we support is the floppy and we have a hack
         * in the floppy driver directly to get a device for us.
         */
-       if (unlikely(dev == NULL))
-               return NULL;
-
-       return dev->archdata.dma_ops;
+       if (dev && dev->archdata.dma_ops)
+               return dev->archdata.dma_ops;
+       /*
+        * In some cases (for example, use the Intel(R) 10 Gigabit PCI
+        * expression Virtual Function Network Driver -- ixgbevf.ko),
+        * their value of dev is the NULL. If return NULL, the driver is
+        * aborting. So return dma_direct_ops variable when dev == NULL.
+        */
+       return &dma_direct_ops;
  }
  
  static inline void set_dma_ops(struct device *dev, struct dma_map_ops *ops)






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