Re: [PATCH] of: of_reserved_mem: Increase limit for reserved_mem regions

[Rob Herring <robh+dt@kernel.org>]

On Wed, Apr 20, 2022 at 4:09 PM Patrick Daly <quic_pdaly@quicinc.com> wrote:
>
> The reserved_mem array must be statically allocated because it is used
> prior to memblock being aware of all "no-map" or otherwise reserved
> regions which have fixed physical addresses. Due to this limitation,
> if one architecture/board has a large number of reserved_mem regions,
> this limit must be raised for all.
>
> In particular, certain new qcom boards currently have 63 reserved memory
> regions, which when new features are added, pushes them over the existing
> limit of 64.

Please revive this instead:

https://lore.kernel.org/all/20211119075844.2902592-3-calvinzhang.cool@gmail.com/

>
> A generalized breakdown by region type:
> 13 for linux-loaded device firmware

If loaded by linux, why do you need fixed carveouts in DT? The devices
can't be told what address their fw is at?

> 9 for guest-vms or inter-vm communication

Why does that need to be in DT?

> 15 cma heaps/dma-buf heaps

Sounds like not trusting the OS to allocate memory itself. From what
I've read, the kernel's memory allocation abilities are better now
than when CMA was added.

> 24 for bootloaders/hypervisor/secure-world devices or software
> 2 misc
>
> Although this number could be reduced by a minor amount by combining
> physically adjacent regions, this comes at the cost of losing
> documention on what/who the regions are used by. In addition, combining
> adjacent regions is not possible if there are phandles in devicetree
> referring to the regions in question, such as "memory-region".
>
> Vmlinux before:
> text      data      bss     dec       hex      filename
> 31030829  15807732  588524  47427085  2d3ae0d  dist/vmlinux
>
> Vmlinux after:
> text      data      bss     dec       hex      filename
> 31030877  15807668  592108  47430653  2d3bbfd  dist/vmlinux
>
> Signed-off-by: Patrick Daly <quic_pdaly@quicinc.com>
> ---
>  drivers/of/of_reserved_mem.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
> index 75caa6f..de0cdda 100644
> --- a/drivers/of/of_reserved_mem.c
> +++ b/drivers/of/of_reserved_mem.c
> @@ -26,7 +26,7 @@
>
>  #include "of_private.h"
>
> -#define MAX_RESERVED_REGIONS   64
> +#define MAX_RESERVED_REGIONS   128
>  static struct reserved_mem reserved_mem[MAX_RESERVED_REGIONS];
>  static int reserved_mem_count;
>
> --
> 2.7.4
>