> From: Simon Glass <s...@chromium.org>
> Date: Sun, 19 Sep 2021 21:16:00 -0600
>
> Hi Mark,
>
> On Sat, 18 Sept 2021 at 07:55, Mark Kettenis <kette...@openbsd.org> wrote:
> >
> > The DART is an IOMMU that is used on Apple's M1 SoC. This driver
> > supports the DART in bypass mode as well as in a mode where it
> > creates a 1:1 mapping of a subset of RAM as not all DARTs support
> > bypass mode. The USB3 ports integrated on the SoC use a DART
> > that supports bypass mode. The 1:1 mapping will be used in the
> > future to support other devices such as the PCIe host bridge
> > of the M1 SoC.
> >
> > Signed-off-by: Mark Kettenis <kette...@openbsd.org>
> > ---
> > drivers/misc/Kconfig | 7 ++
> > drivers/misc/Makefile | 1 +
> > drivers/misc/apple_dart.c | 171 ++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 179 insertions(+)
> > create mode 100644 drivers/misc/apple_dart.c
> >
> > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> > index 997b713221..d70b060e74 100644
> > --- a/drivers/misc/Kconfig
> > +++ b/drivers/misc/Kconfig
> > @@ -38,6 +38,13 @@ config ALTERA_SYSID
> > Select this to enable a sysid for Altera devices. Please find
> > details on the "Embedded Peripherals IP User Guide" of Altera.
> >
> > +config APPLE_DART
> > + bool "Apple DART support"
> > + depends on MISC && ARCH_APPLE
> > + default y
> > + help
> > + Enable support for the DART on Apple SoCs.
>
> Should have at least 3 lines. E.g. what does DART stand for, what does
> it do and what does the driver support?
Sure. The DART is what we usually call an IOMMU.
> > +
> > config ATSHA204A
> > bool "Support for Atmel ATSHA204A module"
> > depends on MISC
> > diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> > index b64cd2a4de..f666cd392d 100644
> > --- a/drivers/misc/Makefile
> > +++ b/drivers/misc/Makefile
> > @@ -29,6 +29,7 @@ endif
> > endif
> > obj-$(CONFIG_ALI152X) += ali512x.o
> > obj-$(CONFIG_ALTERA_SYSID) += altera_sysid.o
> > +obj-$(CONFIG_APPLE_DART) += apple_dart.o
> > obj-$(CONFIG_ATSHA204A) += atsha204a-i2c.o
> > obj-$(CONFIG_CBMEM_CONSOLE) += cbmem_console.o
> > obj-$(CONFIG_DS4510) += ds4510.o
> > diff --git a/drivers/misc/apple_dart.c b/drivers/misc/apple_dart.c
> > new file mode 100644
> > index 0000000000..f619a624d0
> > --- /dev/null
> > +++ b/drivers/misc/apple_dart.c
> > @@ -0,0 +1,171 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Copyright (C) 2021 Mark Kettenis <kette...@openbsd.org>
> > + */
> > +
> > +#include <common.h>
> > +#include <clk.h>
> > +#include <cpu_func.h>
> > +#include <dm.h>
> > +#include <mapmem.h>
> > +#include <asm/io.h>
> > +
> > +#define DART_PARAMS2 0x0004
> > +#define DART_PARAMS2_BYPASS_SUPPORT BIT(0)
> > +#define DART_TLB_OP 0x0020
> > +#define DART_TLB_OP_OPMASK (0xfff << 20)
> > +#define DART_TLB_OP_FLUSH (0x001 << 20)
> > +#define DART_TLB_OP_BUSY BIT(2)
> > +#define DART_TLB_OP_SIDMASK 0x0034
> > +#define DART_ERROR_STATUS 0x0040
> > +#define DART_TCR(sid) (0x0100 + 4 * (sid))
> > +#define DART_TCR_TRANSLATE_ENABLE BIT(7)
> > +#define DART_TCR_BYPASS_DART BIT(8)
> > +#define DART_TCR_BYPASS_DAPF BIT(12)
> > +#define DART_TTBR(sid, idx) (0x0200 + 16 * (sid) + 4 * (idx))
> > +#define DART_TTBR_VALID BIT(31)
> > +#define DART_TTBR_SHIFT 12
> > +
> > +struct apple_dart_priv {
>
> How about s/apple_dart/dart/ ?
>
> It makes the code easier to read.
I think using apple_dart_ consistently as a prefix makes more sense.
> > + struct clk_bulk clks;
> > + void *base;
> > +};
> > +
> > +dma_addr_t apple_dart_bus_start;
> > +phys_addr_t apple_dart_phys_start;
> > +phys_size_t apple_dart_size = SZ_512M;
>
> Try to avoid variables in drivers. Can these go in a priv struct?
Not really since the intent is that these variables specify a global
"window" that is mapped 1:1 into all the DARTs.
> > +
> > +static void apple_dart_flush_tlb(struct apple_dart_priv *priv)
>
> comments on these functions
>
> > +{
> > + u32 status;
> > +
> > + writel(0xffffffff, priv->base + DART_TLB_OP_SIDMASK);
> > + writel(DART_TLB_OP_FLUSH, priv->base + DART_TLB_OP);
> > +
> > + for (;;) {
> > + status = readl(priv->base + DART_TLB_OP);
> > + if ((status & DART_TLB_OP_OPMASK) == 0)
> > + break;
> > + if ((status & DART_TLB_OP_BUSY) == 0)
> > + break;
> > + }
> > +}
> > +
> > +static int apple_dart_clk_init(struct udevice *dev,
> > + struct apple_dart_priv *priv)
> > +{
> > + int ret;
> > +
> > + ret = clk_get_bulk(dev, &priv->clks);
> > + if (ret == -ENOSYS || ret == -ENOENT)
>
> Does -ENOSYS not indicate an error? If it doesn't, I think a comment
> would help here.
So we just learned that what we previously considered to be clocks are
really better modelled as power domains. So this code will go away.
> > + return 0;
> > + if (ret)
> > + return ret;
> > +
> > + ret = clk_enable_bulk(&priv->clks);
> > + if (ret) {
> > + clk_release_bulk(&priv->clks);
> > + return ret;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static int apple_dart_bind(struct udevice *dev)
> > +{
> > + void *base;
> > + int sid, i;
> > +
> > + base = dev_read_addr_ptr(dev);
> > + if (!base)
> > + return -EINVAL;
> > +
> > + u32 params2 = readl(base + DART_PARAMS2);
> > + if (params2 & DART_PARAMS2_BYPASS_SUPPORT) {
> > + for (sid = 0; sid < 16; sid++) {
> > + writel(DART_TCR_BYPASS_DART | DART_TCR_BYPASS_DAPF,
> > + base + DART_TCR(sid));
> > + for (i = 0; i < 4; i++)
> > + writel(0, base + DART_TTBR(sid, i));
> > + }
> > + }
>
> Not allowed hardware access in bind(). Can this more to probe() ?
Well, I need to make sure that this happens before other drivers get
probed (in particular the xhci-dwc3 driver). Is there a better
mechanism to achieve that?
> > +
> > + return 0;
> > +}
> > +
> > +static int apple_dart_probe(struct udevice *dev)
> > +{
> > + struct apple_dart_priv *priv = dev_get_priv(dev);
> > + phys_addr_t phys;
> > + u64 *l1, *l2;
> > + int sid, i, j;
> > + int ret;
> > +
> > + apple_dart_phys_start = gd->ram_top - apple_dart_size;
> > +
> > + priv->base = dev_read_addr_ptr(dev);
> > + if (!priv->base)
> > + return -EINVAL;
> > +
> > + ret = apple_dart_clk_init(dev, priv);
> > + if (ret)
> > + return ret;
> > +
> > + l1 = memalign(SZ_64K, SZ_64K);
> > + memset(l1, 0, SZ_64K);
> > +
> > + i = 0;
> > + phys = apple_dart_phys_start;
> > + while (phys < apple_dart_phys_start + apple_dart_size) {
> > + l2 = memalign(SZ_16K, SZ_16K);
>
> check for error
>
> > + memset(l2, 0, SZ_16K);
> > +
> > + for (j = 0; j < 2048; j++) {
> > + l2[j] = phys | 0x3;
> > + phys += SZ_16K;
> > + }
> > + flush_dcache_range((unsigned long)l2,
> > + (unsigned long)l2 + SZ_16K);
> > +
> > + l1[i++] = (phys_addr_t)l2 | 0x8 | 0x3;
>
> Do you need the cast? What are the magic numbers here? Can you use an
> enum/#define ?
Not sure if we know the exact meaning of those bits yet. But there is
a Linux driver now, so maybe I need to look at it again.
> > + }
> > +
> > + flush_dcache_range((unsigned long)l1, (unsigned long)l1 + SZ_64K);
> > +
> > + for (sid = 0; sid < 16; sid++) {
>
> comment,...what is this doing?
>
> > + for (i = 0; i < 4; i++)
> > + writel(0, priv->base + DART_TTBR(sid, i));
> > + }
> > +
> > + apple_dart_flush_tlb(priv);
> > +
> > + for (sid = 0; sid < 16; sid++) {
> > + phys = (phys_addr_t)l1;
> > + for (i = 0; i < 4; i++) {
> > + writel((phys >> DART_TTBR_SHIFT) | DART_TTBR_VALID,
> > + priv->base + DART_TTBR(sid, i));
> > + phys += SZ_16K;
> > + }
> > + }
> > +
> > + apple_dart_flush_tlb(priv);
> > +
> > + for (sid = 0; sid < 16; sid++)
> > + writel(DART_TCR_TRANSLATE_ENABLE, priv->base +
> > DART_TCR(sid));
> > +
> > + return 0;
> > +}
> > +
> > +static const struct udevice_id apple_dart_ids[] = {
> > + { .compatible = "apple,t8103-dart" },
> > + { /* sentinel */ }
> > +};
> > +
> > +U_BOOT_DRIVER(apple_dart) = {
> > + .name = "apple_dart",
> > + .id = UCLASS_MISC,
> > + .of_match = apple_dart_ids,
> > + .priv_auto = sizeof(struct apple_dart_priv),
> > + .bind = apple_dart_bind,
> > + .probe = apple_dart_probe
> > +};
> > --
> > 2.33.0
> >
>
> Regards,
> Simon
>
