Hello Théo,
On Fri, 21 Mar 2025 20:09:39 +0100
Théo Lebrun [off-list ref] wrote:
Introduce macb_dma_is_64b() and macb_dma_is_ptp() helper functions.
Many codepaths are made simpler by dropping conditional compilation.
This implies three changes:
- Always compile related structure definitions inside <macb.h>.
- Make the field hw_dma_cap in struct macb always present.
- MACB_EXT_DESC can be dropped as it is useless now.
The common case is:
#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
struct macb_dma_desc_64 *desc_64;
if (bp->hw_dma_cap & HW_DMA_CAP_64B) {
desc_64 = macb_64b_desc(bp, desc);
// ...
}
#endif
And replaced by:
struct macb_dma_desc_64 *desc_64;
if (macb_dma_is_64b(bp)) {
desc_64 = macb_64b_desc(bp, desc);
// ...
}
Just a thought, but this is adding some more branches in the hotpath on
32 bits DMA setups. Did you measure any performance changes on
these platforms (if you have access to one :) )
As the caps can't be changed dynamically, maybe these helpers could be
replaced more efficiently with some static_key ? This would benefit
both 32 and 64 bits systems as the following would be more efficient
if (bp->hw_dma_cap & HW_DMA_CAP_64B) {
// ...
}
Just a thought of course, maybe this patch doesn't really hurt perfs :)
Maxime