From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: Jeremy Linton <jeremy.linton@arm.com>,
Ard Biesheuvel <ardb@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>,
Frank Rowand <frowand.list@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
iommu@lists.linux-foundation.org,
Rob Herring <robh+dt@kernel.org>,
linux-rpi-kernel@lists.infradead.org,
Will Deacon <will@kernel.org>, Christoph Hellwig <hch@lst.de>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH 1/4] of/fdt: Update zone_dma_bits when running in bcm2711
Date: Fri, 09 Oct 2020 10:37:50 +0200 [thread overview]
Message-ID: <e5e724bc6f07c766f1f4188729d0b757dea363f3.camel@suse.de> (raw)
In-Reply-To: <978e01a1-71e6-7286-0876-bb10698ba1d2@arm.com>
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Hi Jeremy.
On Thu, 2020-10-08 at 22:59 -0500, Jeremy Linton wrote:
> On 10/8/20 2:43 PM, Ard Biesheuvel wrote:
> > (+ Lorenzo)
> >
> > On Thu, 8 Oct 2020 at 12:14, Catalin Marinas <catalin.marinas@arm.com> wrote:
> > > On Thu, Oct 08, 2020 at 12:05:25PM +0200, Nicolas Saenz Julienne wrote:
> > > > On Fri, 2020-10-02 at 12:55 +0100, Catalin Marinas wrote:
> > > > > On Thu, Oct 01, 2020 at 07:31:19PM +0200, Nicolas Saenz Julienne wrote:
> > > > > > On Thu, 2020-10-01 at 18:23 +0100, Catalin Marinas wrote:
> > > > > > > On Thu, Oct 01, 2020 at 06:15:01PM +0100, Catalin Marinas wrote:
> > > > > > > > On Thu, Oct 01, 2020 at 06:17:37PM +0200, Nicolas Saenz Julienne wrote:
> > > > > > > > > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> > > > > > > > > index 4602e467ca8b..cd0d115ef329 100644
> > > > > > > > > --- a/drivers/of/fdt.c
> > > > > > > > > +++ b/drivers/of/fdt.c
> > > > > > > > > @@ -25,6 +25,7 @@
> > > > > > > > > #include <linux/serial_core.h>
> > > > > > > > > #include <linux/sysfs.h>
> > > > > > > > > #include <linux/random.h>
> > > > > > > > > +#include <linux/dma-direct.h> /* for zone_dma_bits */
> > > > > > > > >
> > > > > > > > > #include <asm/setup.h> /* for COMMAND_LINE_SIZE */
> > > > > > > > > #include <asm/page.h>
> > > > > > > > > @@ -1198,6 +1199,14 @@ void __init early_init_dt_scan_nodes(void)
> > > > > > > > > of_scan_flat_dt(early_init_dt_scan_memory, NULL);
> > > > > > > > > }
> > > > > > > > >
> > > > > > > > > +void __init early_init_dt_update_zone_dma_bits(void)
> > > > > > > > > +{
> > > > > > > > > + unsigned long dt_root = of_get_flat_dt_root();
> > > > > > > > > +
> > > > > > > > > + if (of_flat_dt_is_compatible(dt_root, "brcm,bcm2711"))
> > > > > > > > > + zone_dma_bits = 30;
> > > > > > > > > +}
> > > > > > > >
> > > > > > > > I think we could keep this entirely in the arm64 setup_machine_fdt() and
> > > > > > > > not pollute the core code with RPi4-specific code.
> > > > > > >
> > > > > > > Actually, even better, could we not move the check to
> > > > > > > arm64_memblock_init() when we initialise zone_dma_bits?
> > > > > >
> > > > > > I did it this way as I vaguely remembered Rob saying he wanted to centralise
> > > > > > all early boot fdt code in one place. But I'll be happy to move it there.
> > > > >
> > > > > I can see Rob replied and I'm fine if that's his preference. However,
> > > > > what I don't particularly like is that in the arm64 code, if
> > > > > zone_dma_bits == 24, we set it to 32 assuming that it wasn't touched by
> > > > > the early_init_dt_update_zone_dma_bits(). What if at some point we'll
> > > > > get a platform that actually needs 24 here (I truly hope not, but just
> > > > > the principle of relying on magic values)?
> > > > >
> > > > > So rather than guessing, I'd prefer if the arch code can override
> > > > > ZONE_DMA_BITS_DEFAULT. Then, in arm64, we'll just set it to 32 and no
> > > > > need to explicitly touch the zone_dma_bits variable.
> > > >
> > > > Yes, sonds like the way to go. TBH I wasn't happy with that solution either,
> > > > but couldn't think of a nicer alternative.
> > > >
> > > > Sadly I just realised that the series is incomplete, we have RPi4 users that
> > > > want to boot unsing ACPI, and this series would break things for them. I'll
> > > > have a word with them to see what we can do for their use-case.
> > >
> > > Is there a way to get some SoC information from ACPI?
> > >
> >
> > This is unfortunate. We used ACPI _DMA methods as they were designed
> > to communicate the DMA limit of the XHCI controller to the OS.
> >
> > It shouldn't be too hard to match the OEM id field in the DSDT, and
> > switch to the smaller mask. But it sucks to have to add a quirk like
> > that.
> > It also requires delaying setting the arm64_dma_phy_limit a bit, but
> that doesn't appear to be causing a problem. I've been boot/compiling
> with a patch like:
>
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> index cada0b816c8a..9dfe776c1c75 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -14,6 +14,7 @@
>
> #include <linux/acpi.h>
> #include <linux/cpumask.h>
> +#include <linux/dma-direct.h>
> #include <linux/efi.h>
> #include <linux/efi-bgrt.h>
> #include <linux/init.h>
> @@ -168,6 +169,11 @@ static int __init acpi_fadt_sanity_check(void)
> ret = -EINVAL;
> }
>
> + if (!strncmp(table->oem_id, "RPIFDN", ACPI_OEM_ID_SIZE) &&
> + !strncmp(table->oem_table_id, "RPI4 ",
> ACPI_OEM_TABLE_ID_SIZE) &&
> + table->oem_revision <= 0x200) {
> + zone_dma_bits = 30;
> + }
> out:
> /*
> * acpi_get_table() creates FADT table mapping that
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index cd5caca8a929..6c8aaf1570ce 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -195,6 +195,7 @@ static void __init zone_sizes_init(unsigned long
> min, unsigned long max)
> unsigned long max_zone_pfns[MAX_NR_ZONES] = {0};
>
> #ifdef CONFIG_ZONE_DMA
> + arm64_dma_phys_limit = max_zone_phys(zone_dma_bits);
> max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit);
> #endif
> #ifdef CONFIG_ZONE_DMA32
> @@ -393,7 +394,6 @@ void __init arm64_memblock_init(void)
> */
> if (zone_dma_bits == ZONE_DMA_BITS_DEFAULT)
> zone_dma_bits = 32;
> - arm64_dma_phys_limit = max_zone_phys(zone_dma_bits);
> }
>
> if (IS_ENABLED(CONFIG_ZONE_DMA32))
>
>
Thanks for taking the time to look at this!
Regards,
Nicolas
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next prev parent reply other threads:[~2020-10-09 8:38 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-01 16:17 [PATCH 0/4] arm64: Default to 32-bit wide ZONE_DMA Nicolas Saenz Julienne
2020-10-01 16:17 ` [PATCH 1/4] of/fdt: Update zone_dma_bits when running in bcm2711 Nicolas Saenz Julienne
2020-10-01 17:15 ` Catalin Marinas
2020-10-01 17:23 ` Catalin Marinas
2020-10-01 17:31 ` Nicolas Saenz Julienne
2020-10-01 20:02 ` Rob Herring
2020-10-02 11:55 ` Catalin Marinas
2020-10-08 10:05 ` Nicolas Saenz Julienne
2020-10-08 10:13 ` Catalin Marinas
2020-10-08 19:43 ` Ard Biesheuvel
2020-10-09 3:59 ` Jeremy Linton
2020-10-09 8:37 ` Nicolas Saenz Julienne [this message]
2020-10-09 7:10 ` Christoph Hellwig
2020-10-09 7:37 ` Ard Biesheuvel
2020-10-09 8:36 ` Nicolas Saenz Julienne
2020-10-09 9:13 ` Ard Biesheuvel
2020-10-09 13:33 ` Nicolas Saenz Julienne
2020-10-09 15:24 ` Lorenzo Pieralisi
2020-10-09 16:23 ` Ard Biesheuvel
2020-10-09 17:10 ` Catalin Marinas
2020-10-10 10:36 ` Ard Biesheuvel
2020-10-10 10:53 ` Nicolas Saenz Julienne
2020-10-10 12:38 ` Catalin Marinas
2020-10-12 6:47 ` Christoph Hellwig
2020-10-12 8:47 ` Catalin Marinas
2020-10-02 9:05 ` kernel test robot
2020-10-01 16:17 ` [PATCH 2/4] dma-direct: Turn zone_dma_bits default value into a define Nicolas Saenz Julienne
2020-10-01 16:17 ` [PATCH 3/4] arm64: Default to 32-bit ZONE_DMA Nicolas Saenz Julienne
2020-10-01 17:19 ` Catalin Marinas
2020-10-01 16:17 ` [PATCH 4/4] mm: Update DMA zones description Nicolas Saenz Julienne
2020-10-01 17:19 ` Catalin Marinas
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