Patch "arm64: mm: Set ZONE_DMA size based on devicetree's dma-ranges" has been added to the 5.10-stable tree

[gregkh at linuxfoundation.org]

This is a note to let you know that I've just added the patch titled

    arm64: mm: Set ZONE_DMA size based on devicetree's dma-ranges

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm64-mm-set-zone_dma-size-based-on-devicetree-s-dma-ranges.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable at vger.kernel.org> know about it.


>From foo at baz Sun Mar  7 04:22:37 PM CET 2021
From: Jing Xiangfeng <jingxiangfeng at huawei.com>
Date: Wed, 3 Mar 2021 15:33:17 +0800
Subject: arm64: mm: Set ZONE_DMA size based on devicetree's dma-ranges
To: <gregkh at linuxfoundation.org>, <catalin.marinas at arm.com>, <will at kernel.org>, <akpm at linux-foundation.org>, <nsaenzjulienne at suse.de>, <paul.walmsley at sifive.com>, <palmer at dabbelt.com>, <aou at eecs.berkeley.edu>, <rppt at kernel.org>, <lorenzo.pieralisi at arm.com>, <guohanjun at huawei.com>, <sudeep.holla at arm.com>, <rjw at rjwysocki.net>, <lenb at kernel.org>, <song.bao.hua at hisilicon.com>, <ardb at kernel.org>, <anshuman.khandual at arm.com>, <bhelgaas at google.com>, <guro at fb.com>, <robh+dt at kernel.org>
Cc: <stable at vger.kernel.org>, <linux-arm-kernel at lists.infradead.org>, <frowand.list at gmail.com>, <devicetree at vger.kernel.org>, <linux-kernel at vger.kernel.org>, <linux-mm at kvack.org>, <linux-riscv at lists.infradead.org>, <jingxiangfeng at huawei.com>, <wangkefeng.wang at huawei.com>
Message-ID: <20210303073319.2215839-6-jingxiangfeng at huawei.com>

From: Nicolas Saenz Julienne <nsaenzjulienne at suse.de>

commit 8424ecdde7df99d5426e1a1fd9f0fb36f4183032 upstream

We recently introduced a 1 GB sized ZONE_DMA to cater for platforms
incorporating masters that can address less than 32 bits of DMA, in
particular the Raspberry Pi 4, which has 4 or 8 GB of DRAM, but has
peripherals that can only address up to 1 GB (and its PCIe host
bridge can only access the bottom 3 GB)

The DMA layer also needs to be able to allocate memory that is
guaranteed to meet those DMA constraints, for bounce buffering as well
as allocating the backing for consistent mappings. This is why the 1 GB
ZONE_DMA was introduced recently. Unfortunately, it turns out the having
a 1 GB ZONE_DMA as well as a ZONE_DMA32 causes problems with kdump, and
potentially in other places where allocations cannot cross zone
boundaries. Therefore, we should avoid having two separate DMA zones
when possible.

So, with the help of of_dma_get_max_cpu_address() get the topmost
physical address accessible to all DMA masters in system and use that
information to fine-tune ZONE_DMA's size. In the absence of addressing
limited masters ZONE_DMA will span the whole 32-bit address space,
otherwise, in the case of the Raspberry Pi 4 it'll only span the 30-bit
address space, and have ZONE_DMA32 cover the rest of the 32-bit address
space.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne at suse.de>
Link: https://lore.kernel.org/r/20201119175400.9995-6-nsaenzjulienne@suse.de
Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
Cc: <stable at vger.kernel.org>
Signed-off-by: Jing Xiangfeng <jingxiangfeng at huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 arch/arm64/mm/init.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -42,8 +42,6 @@
 #include <asm/tlb.h>
 #include <asm/alternative.h>
 
-#define ARM64_ZONE_DMA_BITS	30
-
 /*
  * We need to be able to catch inadvertent references to memstart_addr
  * that occur (potentially in generic code) before arm64_memblock_init()
@@ -188,9 +186,11 @@ static phys_addr_t __init max_zone_phys(
 static void __init zone_sizes_init(unsigned long min, unsigned long max)
 {
 	unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
+	unsigned int __maybe_unused dt_zone_dma_bits;
 
 #ifdef CONFIG_ZONE_DMA
-	zone_dma_bits = ARM64_ZONE_DMA_BITS;
+	dt_zone_dma_bits = fls64(of_dma_get_max_cpu_address(NULL));
+	zone_dma_bits = min(32U, dt_zone_dma_bits);
 	arm64_dma_phys_limit = max_zone_phys(zone_dma_bits);
 	max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit);
 #endif


Patches currently in stable-queue which might be from jingxiangfeng at huawei.com are

queue-5.10/of-unittest-add-test-for-of_dma_get_max_cpu_address.patch
queue-5.10/mm-remove-examples-from-enum-zone_type-comment.patch
queue-5.10/arm64-mm-set-zone_dma-size-based-on-devicetree-s-dma-ranges.patch
queue-5.10/of-address-introduce-of_dma_get_max_cpu_address.patch
queue-5.10/arm64-mm-move-zone_dma_bits-initialization-into-zone_sizes_init.patch
queue-5.10/arm64-mm-set-zone_dma-size-based-on-early-iort-scan.patch
queue-5.10/arm64-mm-move-reserve_crashkernel-into-mem_init.patch