RE: [EXT] Re: [PATCH] arm64: mm: Fix SOCs with DDR starting above zero
From: Elad Nachman
Date: Thu Jan 04 2024 - 13:35:14 EST
> -----Original Message-----
> From: Florian Fainelli <florian.fainelli@xxxxxxxxxxxx>
> Sent: Thursday, January 4, 2024 8:29 PM
> To: Elad Nachman <enachman@xxxxxxxxxxx>; Will Deacon
> <will@xxxxxxxxxx>
> Cc: catalin.marinas@xxxxxxx; thunder.leizhen@xxxxxxxxxx;
> bhe@xxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; yajun.deng@xxxxxxxxx;
> chris.zjh@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-arm-
> kernel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [EXT] Re: [PATCH] arm64: mm: Fix SOCs with DDR starting above
> zero
>
> On 1/4/24 04:38, Elad Nachman wrote:
> >
> >
> >> -----Original Message-----
> >> From: Florian Fainelli <florian.fainelli@xxxxxxxxxxxx>
> >> Sent: Wednesday, January 3, 2024 8:32 PM
> >> To: Will Deacon <will@xxxxxxxxxx>; Elad Nachman
> >> <enachman@xxxxxxxxxxx>
> >> Cc: catalin.marinas@xxxxxxx; thunder.leizhen@xxxxxxxxxx;
> >> bhe@xxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; yajun.deng@xxxxxxxxx;
> >> chris.zjh@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-arm-
> >> kernel@xxxxxxxxxxxxxxxxxxx
> >> Subject: [EXT] Re: [PATCH] arm64: mm: Fix SOCs with DDR starting above
> >> zero
> >>
> >> External Email
> >>
> >> ----------------------------------------------------------------------
> >> 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@xxxxxxxxxxx>
> >>>>
> >>>> 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@xxxxxxxxxxx>
> >>>> ---
> >>>> 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:
> >
> > That is below 4GB
>
> Right, I was just making sure that there would be no regressions with
> non-zero base addresses for DRAM, not that there should be, but getting
> Tested-by tags for such changes is always a good thing IMHO.
I do not have such board nor access to one.
Perhaps someone on your side can test this patch on the SOC which has DDR starting at 0x4000_0000 for regression?
Probably a quick one, boot + DMA sanity test.
Thanks,
>
> >
> >>
> >> 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@fe000000
> >> [ 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@be000000
> >> [ 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
> >
> > Do you have an example where this works when DDR memory starts above
> 4GB?
> > The code in max_zone_phys() has separate if clauses for memory starting
> above 4GB,
> > and for memory starting above zone mask but below 4GB...
>
> I am afraid I don't have such a system handy. The one with 2+2GB with
> the second 2GB starting at 12GB might be a tad difficult to start
> without the first 2GB due to a number of critical reserved memory
> regions being there.
> --
> Florian
Elad.