Re: Re: [PATCH] [PATCH] ARM64: Setup DMA32 zone size by bootargs

2020-09-25 Thread Catalin Marinas
On Thu, Sep 24, 2020 at 10:15:14PM +0800, Phil Chang wrote: > Actually, In a embedded system with 3GB memory, the memory bus width is not > the same among the 3GB. > (The first 2GB is 48-bit wide, and the latter 1GB is 16-bit wide.) So I guess that's the data bus width. Devices can still access

Re: Re: [PATCH] [PATCH] ARM64: Setup DMA32 zone size by bootargs

2020-09-24 Thread Phil Chang
Actually, In a embedded system with 3GB memory, the memory bus width is not the same among the 3GB. (The first 2GB is 48-bit wide, and the latter 1GB is 16-bit wide.) For memory throughput reason of hardware IPs, we need allocate memory from the first 2GB for the hardware IPs. And that is why we

Re: [PATCH] [PATCH] ARM64: Setup DMA32 zone size by bootargs

2020-09-16 Thread Catalin Marinas
On Wed, Sep 16, 2020 at 09:33:24PM +0800, Phil Chang wrote: > this patch allowing the DMA32 zone be configurable in ARM64. > For some devices, the main memory split into 2 part due to the memory > architecture, the efficient and less inefficient part. > One of the use case is fine-tune the dma32

[PATCH] [PATCH] ARM64: Setup DMA32 zone size by bootargs

2020-09-16 Thread Phil Chang
this patch allowing the DMA32 zone be configurable in ARM64. For some devices, the main memory split into 2 part due to the memory architecture, the efficient and less inefficient part. One of the use case is fine-tune the dma32 size to contain all the efficient part of memory block on this kind

Re: [PATCH] [PATCH] ARM64: Setup DMA32 zone size by bootargs

2020-09-16 Thread Christoph Hellwig
On Wed, Sep 16, 2020 at 03:22:06PM +0800, Phil Chang wrote: > this patch allowing the DMA32 zone be configurable in ARM64. Hell no. The point of the DMA32 zone is that it is exactly the first 4GiG, and not some random size someone decided without explaining why.

[PATCH] [PATCH] ARM64: Setup DMA32 zone size by bootargs

2020-09-16 Thread Phil Chang
this patch allowing the DMA32 zone be configurable in ARM64. Signed-off-by: Alix Wu Signed-off-by: YJ Chiang Signed-off-by: Phil Chang --- For some devices, the main memory split into 2 part due to the memory architecture, the efficient and less inefficient part. One of the use case is

[PATCH] [PATCH] ARM64: Setup DMA32 zone size by bootargs

2020-09-15 Thread Phil Chang
Allowing the DMA32 zone be configurable in ARM64 but at most 4Gb. Signed-off-by: Alix Wu Signed-off-by: YJ Chiang Signed-off-by: Phil Chang --- .../admin-guide/kernel-parameters.txt | 3 ++ arch/arm64/include/asm/memory.h | 2 + arch/arm64/mm/init.c

Re: [PATCH] [PATCH] ARM64: Setup DMA32 zone size by bootargs

2020-09-15 Thread Mike Rapoport
On Tue, Sep 15, 2020 at 11:08:55PM +0800, Phil Chang wrote: > Allowing the DMA32 zone be configurable in ARM64 but at most 4Gb. Please add more details why would you like to limit the DMA32 zone. > Signed-off-by: Alix Wu > Signed-off-by: YJ Chiang > Signed-off-by: Phil Chang > --- > >

Re: [PATCH] [PATCH] ARM64: Setup DMA32 zone size by bootargs

2020-09-15 Thread David Woodhouse
On 15 September 2020 16:08:55 BST, Phil Chang wrote: >Allowing the DMA32 zone be configurable in ARM64 but at most 4Gb. I don't think 4,000,000 bits is a particularly sensible limit. Perhaps you meant bytes, and perhaps you meant 4*1024*1024? That would be "4 GiB". -- Sent from my Android

Re: [PATCH] [PATCH] ARM64: Setup DMA32 zone size by bootargs

2020-09-15 Thread Catalin Marinas
On Tue, Sep 15, 2020 at 11:08:55PM +0800, Phil Chang wrote: > Allowing the DMA32 zone be configurable in ARM64 but at most 4Gb. Why? What is your use-case? -- Catalin