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Message-ID: <fc6f3fff-9915-4ffd-93f0-a633d5662147@broadcom.com>
Date: Wed, 3 Jan 2024 10:32:28 -0800
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: Will Deacon <will@...nel.org>, Elad Nachman <enachman@...vell.com>
Cc: catalin.marinas@....com, thunder.leizhen@...wei.com, bhe@...hat.com,
akpm@...ux-foundation.org, yajun.deng@...ux.dev, chris.zjh@...wei.com,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm64: mm: Fix SOCs with DDR starting above zero
On 1/3/24 09:45, Will Deacon wrote:
> On Wed, Jan 03, 2024 at 07:00:02PM +0200, Elad Nachman wrote:
>> From: Elad Nachman <enachman@...vell.com>
>>
>> Some SOCs, like the Marvell AC5/X/IM, have a combination
>> of DDR starting at 0x2_0000_0000 coupled with DMA controllers
>> limited to 31 and 32 bit of addressing.
>> This requires to properly arrange ZONE_DMA and ZONE_DMA32 for
>> these SOCs, so swiotlb and coherent DMA allocation would work
>> properly.
>> Change initialization so device tree dma zone bits are taken as
>> function of offset from DRAM start, and when calculating the
>> maximal zone physical RAM address for physical DDR starting above
>> 32-bit, combine the physical address start plus the zone mask
>> passed as parameter.
>> This creates the proper zone splitting for these SOCs:
>> 0..2GB for ZONE_DMA
>> 2GB..4GB for ZONE_DMA32
>> 4GB..8GB for ZONE_NORMAL
>>
>> Signed-off-by: Elad Nachman <enachman@...vell.com>
>> ---
>> arch/arm64/mm/init.c | 20 +++++++++++++++-----
>> 1 file changed, 15 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
>> index 74c1db8ce271..8288c778916e 100644
>> --- a/arch/arm64/mm/init.c
>> +++ b/arch/arm64/mm/init.c
>> @@ -115,20 +115,21 @@ static void __init arch_reserve_crashkernel(void)
>>
>> /*
>> * Return the maximum physical address for a zone accessible by the given bits
>> - * limit. If DRAM starts above 32-bit, expand the zone to the maximum
>> - * available memory, otherwise cap it at 32-bit.
>> + * limit. If DRAM starts above 32-bit, expand the zone to the available memory
>> + * start limited by the zone bits mask, otherwise cap it at 32-bit.
>> */
>> static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
>> {
>> phys_addr_t zone_mask = DMA_BIT_MASK(zone_bits);
>> phys_addr_t phys_start = memblock_start_of_DRAM();
>> + phys_addr_t phys_end = memblock_end_of_DRAM();
>>
>> if (phys_start > U32_MAX)
>> - zone_mask = PHYS_ADDR_MAX;
>> + zone_mask = phys_start | zone_mask;
>> else if (phys_start > zone_mask)
>> zone_mask = U32_MAX;
>>
>> - return min(zone_mask, memblock_end_of_DRAM() - 1) + 1;
>> + return min(zone_mask, phys_end - 1) + 1;
>> }
>>
>> static void __init zone_sizes_init(void)
>> @@ -140,7 +141,16 @@ static void __init zone_sizes_init(void)
>>
>> #ifdef CONFIG_ZONE_DMA
>> acpi_zone_dma_bits = fls64(acpi_iort_dma_get_max_cpu_address());
>> - dt_zone_dma_bits = fls64(of_dma_get_max_cpu_address(NULL));
>> + /*
>> + * When calculating the dma zone bits from the device tree, subtract
>> + * the DRAM start address, in case it does not start from address
>> + * zero. This way. we pass only the zone size related bits to
>> + * max_zone_phys(), which will add them to the base of the DRAM.
>> + * This prevents miscalculations on arm64 SOCs which combines
>> + * DDR starting above 4GB with memory controllers limited to
>> + * 32-bits or less:
>> + */
>> + dt_zone_dma_bits = fls64(of_dma_get_max_cpu_address(NULL) - memblock_start_of_DRAM());
>> zone_dma_bits = min3(32U, dt_zone_dma_bits, acpi_zone_dma_bits);
>> arm64_dma_phys_limit = max_zone_phys(zone_dma_bits);
>> max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit);
>
> Hmm, I'm a bit worried this could regress other platforms since you seem
> to be assuming that DMA address 0 corresponds to the physical start of
> DRAM. What if that isn't the case?
All of our most recent Set-top-box SoCs map DRAM starting at PA
0x4000_0000 FWIW. We have the following memory maps:
1. DRAM mapped at PA 0x0000_0000
2. DRAM mapped at PA 0x4000_0000 with another memory controller starting
at 0x3_0000_0000
3. DRAM mapped at PA 0x4000_0000 with a single memory controller.
Here is the before/after diff with debugging prints introduced to print
start, end, min, mask and the dt_zone_dma_bits value:
Memory map 1. with 2GB -> no change in output
Memory map 2. with 2+2GB -> no change in output
Memory map 3. with 4GB:
@@ -39,7 +39,7 @@
[ 0.000000] OF: reserved mem:
0x00000000fdfff000..0x00000000fdffffff (4 KiB) nomap non-reusable NWMBOX
[ 0.000000] OF: reserved mem:
0x00000000fe000000..0x00000000ffffffff (32768 KiB) nomap non-reusable
SRR@...00000
[ 0.000000] max_zone_phys: start: 0x0000000040000000, end:
0x0000000140000000, min: 0x0000000100000000, mask: 0x00000000ffffffff
-[ 0.000000] zone_sizes_init: dt_zone_dma_bits: 0x00000021
+[ 0.000000] zone_sizes_init: dt_zone_dma_bits: 0x00000020
[ 0.000000] max_zone_phys: start: 0x0000000040000000, end:
0x0000000140000000, min: 0x0000000100000000, mask: 0x00000000ffffffff
[ 0.000000] Zone ranges:
[ 0.000000] DMA [mem 0x0000000040000000-0x00000000ffffffff]
@@ -88,243 +88,243 @@
Memory map 3. with 2GB:
@@ -39,11 +39,11 @@
[ 0.000000] OF: reserved mem:
0x00000000bdfff000..0x00000000bdffffff (4 KiB) nomap non-reusable NWMBOX
[ 0.000000] OF: reserved mem:
0x00000000be000000..0x00000000bfffffff (32768 KiB) nomap non-reusable
SRR@...00000
[ 0.000000] max_zone_phys: start: 0x0000000040000000, end:
0x00000000c0000000, min: 0x00000000c0000000, mask: 0x00000000ffffffff
-[ 0.000000] zone_sizes_init: dt_zone_dma_bits: 0x00000020
-[ 0.000000] max_zone_phys: start: 0x0000000040000000, end:
0x00000000c0000000, min: 0x00000000c0000000, mask: 0x00000000ffffffff
+[ 0.000000] zone_sizes_init: dt_zone_dma_bits: 0x0000001f
+[ 0.000000] max_zone_phys: start: 0x0000000040000000, end:
0x00000000c0000000, min: 0x0000000080000000, mask: 0x000000007fffffff
[ 0.000000] Zone ranges:
-[ 0.000000] DMA [mem 0x0000000040000000-0x00000000bfffffff]
-[ 0.000000] DMA32 empty
+[ 0.000000] DMA [mem 0x0000000040000000-0x000000007fffffff]
+[ 0.000000] DMA32 [mem 0x0000000080000000-0x00000000bfffffff]
[ 0.000000] Normal empty
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
@@ -54,7 +54,7 @@
--
Florian
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