[v2,10/11] arm64: edit zone_dma_bits to fine tune dma-direct min mask
diff mbox series

Message ID 20190820145821.27214-11-nsaenzjulienne@suse.de
State Superseded
Headers show
Series
  • Raspberry Pi 4 DMA addressing support
Related show

Commit Message

Nicolas Saenz Julienne Aug. 20, 2019, 2:58 p.m. UTC
With the introduction of ZONE_DMA in arm64 devices are not forced to
support 32 bit DMA masks. We have to inform dma-direct of this
limitation whenever it happens.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
---

Changes in v2:
- Make sure to filter the higher part of arm64_dma_phys_limit
- Rename variable to zone_dma_bits

 arch/arm64/mm/init.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Comments

Christoph Hellwig Aug. 26, 2019, 7:06 a.m. UTC | #1
On Tue, Aug 20, 2019 at 04:58:18PM +0200, Nicolas Saenz Julienne wrote:
> -	if (IS_ENABLED(CONFIG_ZONE_DMA))
> +	if (IS_ENABLED(CONFIG_ZONE_DMA)) {
>  		arm64_dma_phys_limit = max_zone_dma_phys();
> +		zone_dma_bits = ilog2((arm64_dma_phys_limit - 1) & GENMASK_ULL(31, 0)) + 1;

This adds a way too long line.  I also find the use of GENMASK_ULL
horribly obsfucating, but I know that opinion is't shared by everyone.
Nicolas Saenz Julienne Aug. 26, 2019, 11:08 a.m. UTC | #2
On Mon, 2019-08-26 at 09:06 +0200, Christoph Hellwig wrote:
> On Tue, Aug 20, 2019 at 04:58:18PM +0200, Nicolas Saenz Julienne wrote:
> > -	if (IS_ENABLED(CONFIG_ZONE_DMA))
> > +	if (IS_ENABLED(CONFIG_ZONE_DMA)) {
> >  		arm64_dma_phys_limit = max_zone_dma_phys();
> > +		zone_dma_bits = ilog2((arm64_dma_phys_limit - 1) &
> > GENMASK_ULL(31, 0)) + 1;
>
Hi Christoph,
thanks for the rewiews.

> This adds a way too long line.

I know, I couldn't find a way to split the operation without making it even
harder to read. I'll find a solution.

> I also find the use of GENMASK_ULL
> horribly obsfucating, but I know that opinion is't shared by everyone.

Don't have any preference so I'll happily change it. Any suggestions? Using the
explicit 0xffffffffULL seems hard to read, how about SZ_4GB - 1?
Petr Tesarik Aug. 27, 2019, 7:03 a.m. UTC | #3
On Mon, 26 Aug 2019 13:08:50 +0200
Nicolas Saenz Julienne <nsaenzjulienne@suse.de> wrote:

> On Mon, 2019-08-26 at 09:06 +0200, Christoph Hellwig wrote:
> > On Tue, Aug 20, 2019 at 04:58:18PM +0200, Nicolas Saenz Julienne wrote:  
> > > -	if (IS_ENABLED(CONFIG_ZONE_DMA))
> > > +	if (IS_ENABLED(CONFIG_ZONE_DMA)) {
> > >  		arm64_dma_phys_limit = max_zone_dma_phys();
> > > +		zone_dma_bits = ilog2((arm64_dma_phys_limit - 1) &
> > > GENMASK_ULL(31, 0)) + 1;  
> >  
> Hi Christoph,
> thanks for the rewiews.
> 
> > This adds a way too long line.  
> 
> I know, I couldn't find a way to split the operation without making it even
> harder to read. I'll find a solution.

If all else fails, move the code to an inline function and call it e.g.
phys_limit_to_dma_bits().

Just my two cents,
Petr T

Patch
diff mbox series

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index c51ce79b692b..c5e619f21ad8 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -22,6 +22,7 @@ 
 #include <linux/of_fdt.h>
 #include <linux/dma-mapping.h>
 #include <linux/dma-contiguous.h>
+#include <linux/dma-direct.h>
 #include <linux/efi.h>
 #include <linux/swiotlb.h>
 #include <linux/vmalloc.h>
@@ -437,8 +438,10 @@  void __init arm64_memblock_init(void)
 
 	early_init_fdt_scan_reserved_mem();
 
-	if (IS_ENABLED(CONFIG_ZONE_DMA))
+	if (IS_ENABLED(CONFIG_ZONE_DMA)) {
 		arm64_dma_phys_limit = max_zone_dma_phys();
+		zone_dma_bits = ilog2((arm64_dma_phys_limit - 1) & GENMASK_ULL(31, 0)) + 1;
+	}
 
 	if (IS_ENABLED(CONFIG_ZONE_DMA32))
 		arm64_dma32_phys_limit = max_zone_dma32_phys();