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Date: Wed, 2 Jul 2014 17:39:03 +0100
From: Mark Rutland <mark.rutland@....com>
To: "suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>
Cc: Marc Zyngier <Marc.Zyngier@....com>,
"jason@...edaemon.net" <jason@...edaemon.net>,
Pawel Moll <Pawel.Moll@....com>,
Catalin Marinas <Catalin.Marinas@....com>,
Will Deacon <Will.Deacon@....com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"Harish.Kasiviswanathan@....com" <Harish.Kasiviswanathan@....com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 3/3 V2] irqchip: gic: Add supports for ARM GICv2m MSI(-X)
On Wed, Jul 02, 2014 at 04:22:23PM +0100, suravee.suthikulpanit@....com wrote:
> From: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
>
> ARM GICv2m specification extends GICv2 to support MSI(-X) with
> a new set of register frames. This patch introduces support for
> the non-secure GICv2m register frame.
>
> The driver currently matchs "arm,gic-400-plus" in device tree binding,
> which implements GICv2m.
As far as I am aware, "GIC 400 plus" is not a product name.
> The "msi-controller" keyword in ARM GIC devicetree binding is used to indentify
> GIC driver that it should enable MSI(-X) support, The region of GICv2m MSI
> register frame is specified using the register frame index 4 in the device tree.
> MSI support is optional.
>
> Each GIC maintains an "msi_chip" structure. To discover the msi_chip,
> PCI host driver can do the following:
>
> struct device_node *gic_node = of_irq_find_parent(pdev->dev.of_node);
> pcie_bus->msi_chip = of_pci_find_msi_chip_by_node(gic_node);
>
> Cc: Mark Rutland <Mark.Rutland@....com>
> Cc: Marc Zyngier <Marc.Zyngier@....com>
> Cc: Jason Cooper <jason@...edaemon.net>
> Cc: Catalin Marinas <Catalin.Marinas@....com>
> Cc: Will Deacon <Will.Deacon@....com>
>
> Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
> ---
> Documentation/devicetree/bindings/arm/gic.txt | 19 +-
> drivers/irqchip/Kconfig | 6 +
> drivers/irqchip/Makefile | 1 +
> drivers/irqchip/irq-gic-v2m.c | 248 ++++++++++++++++++++++++++
> drivers/irqchip/irq-gic-v2m.h | 13 ++
> 5 files changed, 284 insertions(+), 3 deletions(-)
> create mode 100644 drivers/irqchip/irq-gic-v2m.c
> create mode 100644 drivers/irqchip/irq-gic-v2m.h
>
> diff --git a/Documentation/devicetree/bindings/arm/gic.txt b/Documentation/devicetree/bindings/arm/gic.txt
> index 5573c08..9e46f7f 100644
> --- a/Documentation/devicetree/bindings/arm/gic.txt
> +++ b/Documentation/devicetree/bindings/arm/gic.txt
> @@ -12,11 +12,13 @@ Main node required properties:
>
> - compatible : should be one of:
> "arm,gic-400"
> + "arm,gic-400-plus"
I am not keen on this name.
> "arm,cortex-a15-gic"
> "arm,cortex-a9-gic"
> "arm,cortex-a7-gic"
> "arm,arm11mp-gic"
> - interrupt-controller : Identifies the node as an interrupt controller
> +
> - #interrupt-cells : Specifies the number of cells needed to encode an
> interrupt source. The type shall be a <u32> and the value shall be 3.
Random (inconsistent) whitespace change?
> @@ -37,9 +39,16 @@ Main node required properties:
> the 8 possible cpus attached to the GIC. A bit set to '1' indicated
> the interrupt is wired to that CPU. Only valid for PPI interrupts.
>
> -- reg : Specifies base physical address(s) and size of the GIC registers. The
> - first region is the GIC distributor register base and size. The 2nd region is
> - the GIC cpu interface register base and size.
> +- reg : Specifies base physical address(s) and size of the GIC register frames.
> +
> + Region | Description
> + Index |
> + -------------------------------------------------------------------
> + 0 | GIC distributor register base and size
> + 1 | GIC cpu interface register base and size
> + 2 | VGIC interface control register base and size (Optional)
> + 3 | VGIC CPU interface register base and size (Optional)
> + 4 | GICv2m MSI interface register base and size (Optional)
As far as I am aware, the MSI interface is completely orthogonal to
having a GICH and GICV.
We should figure out how we expect to handle that (zero-sized reg
entries? reg-names?).
>
> Optional
> - interrupts : Interrupt source of the parent interrupt controller on
> @@ -55,6 +64,10 @@ Optional
> by a crossbar/multiplexer preceding the GIC. The GIC irq
> input line is assigned dynamically when the corresponding
> peripheral's crossbar line is mapped.
> +
> +- msi-controller : Identifies the node as an MSI controller. This requires
> + the register region index 4.
That last clarifying comment is more confusing than helpful.
[...]
> +#define GIC_V2M_MIN_SPI 32
> +#define GIC_V2M_MAX_SPI 1024
GIC interrupt IDs 1020 and above are reserved, no?
Surely the max ID an SPI can take is 1019?
> +#define GIC_OF_MSIV2M_RANGE_INDEX 4
> +
> +/**
> + * alloc_msi_irq - Allocate MSIs from avaialbe MSI bitmap.
> + * @data: Pointer to v2m_data
> + * @nvec: Number of interrupts to allocate
> + * @irq: Pointer to the allocated irq
> + *
> + * Allocates interrupts only if the contiguous range of MSIs
> + * with specified nvec are available. Otherwise return the number
> + * of available interrupts. If none are available, then returns -ENOENT.
> + */
This function is overly complicated, and pointlessly so.
It doesn't achieve anything useful as it returns the size of the _last_
contiguous block rather than the _largest_ contiguous block, and the
only caller (gicv2m_setup_msi_irq) doesn't even care.
Simplify this to just return an error code if allocation is impossible.
> +static int alloc_msi_irq(struct v2m_data *data, int nvec, int *irq)
> +{
> + int size = data->nr_spis;
> + int next = size, i = nvec, ret;
Initialise ret to -ENOENT here...
> +
> + /* We should never allocate more than available nr_spis */
> + if (i >= size)
> + i = size - 1;
...return -ENOENT here...
> +
> + spin_lock(&data->msi_cnt_lock);
> +
> + for (; i > 0; i--) {
> + next = bitmap_find_next_zero_area(data->bm,
> + size, 0, i, 0);
> + if (next < size)
> + break;
> + }
> +
> + if (next >= size || i != nvec) {
> + ret = i ? : -ENOENT;
> + } else {
> + bitmap_set(data->bm, next, nvec);
> + *irq = data->spi_start + next;
> + ret = 0;
> + }
...and change this if-else block to:
if (next < size) {
bitmap_set(data->bm, next, nvec);
*irq = data->spi_start + next;
ret = 0;
}
> +
> + spin_unlock(&data->msi_cnt_lock);
> +
> + return ret;
> +}
[...]
> +static int gicv2m_setup_msi_irq(struct msi_chip *chip, struct pci_dev *pdev,
> + struct msi_desc *desc)
> +{
> + int avail, irq = 0;
> + struct msi_msg msg;
> + phys_addr_t addr;
> + struct v2m_data *data = to_v2m_data(chip);
> +
> + if (!desc) {
> + dev_err(&pdev->dev,
> + "GICv2m: MSI setup failed. Invalid msi descriptor\n");
> + return -EINVAL;
> + }
> +
> + avail = alloc_msi_irq(data, 1, &irq);
> + if (avail != 0) {
> + dev_err(&pdev->dev,
> + "GICv2m: MSI setup failed. Cannnot allocate IRQ\n");
> + return -ENOSPC;
> + }
As mentioned above, in all failure cases for alloc_msi_irq we simply
return -ENOSPC here, so there's no need for alloc_msi_irq to be so
complicated.
We can move the alloc_msi_irq() call into the test, and get rid of the
avail variable.
> + irq_set_chip_data(irq, chip);
> + irq_set_msi_desc(irq, desc);
> + irq_set_irq_type(irq, IRQ_TYPE_EDGE_RISING);
> +
> + addr = data->res.start + MSI_SETSPI_NS;
> +
> + msg.address_hi = (u32)(addr >> 32);
> + msg.address_lo = (u32)(addr);
> + msg.data = irq;
> +#ifdef CONFIG_PCI_MSI
> + write_msi_msg(irq, &msg);
> +#endif
Is it worth doing any of the above if !CONFIG_PCI_MSI?
> + return 0;
> +}
> +
> +static int __init
> +gicv2m_msi_init(struct device_node *node, struct v2m_data *v2m)
> +{
> + unsigned int val;
> +
> + if (of_address_to_resource(node, GIC_OF_MSIV2M_RANGE_INDEX,
> + &v2m->res)) {
> + pr_err("GICv2m: Failed locate GICv2m MSI register frame\n");
> + return -EINVAL;
> + }
> +
> + v2m->base = of_iomap(node, GIC_OF_MSIV2M_RANGE_INDEX);
of_iomap can return NULL...
> + /*
> + * MSI_TYPER:
> + * [31:26] Reserved
> + * [25:16] lowest SPI assigned to MSI
> + * [15:10] Reserved
> + * [9:0] Numer of SPIs assigned to MSI
> + */
> + val = readl_relaxed(v2m->base + MSI_TYPER);
> + if (!val) {
> + pr_warn("GICv2m: Failed to read MSI_TYPER register\n");
> + return -EINVAL;
> + }
> +
> + v2m->spi_start = (val >> 16) & 0x3ff;
> + v2m->nr_spis = val & 0x3ff;
Rather than have the comment above the readl_relaxed, Why not define
some macros for these magic numbers and keep the comment with them?
> +
> + if (v2m->spi_start < GIC_V2M_MIN_SPI ||
> + v2m->nr_spis >= GIC_V2M_MAX_SPI) {
> + pr_err("GICv2m: Init failed\n");
> + return -EINVAL;
> + }
It would be nice to point out why we failed here: the hardware reported
bad values.
> + v2m->bm = kzalloc(sizeof(long) * BITS_TO_LONGS(v2m->nr_spis),
> + GFP_KERNEL);
This looks better than last time :)
[...]
> + ret = of_pci_msi_chip_add(&gic->msi_chip);
> + if (ret) {
> + /* MSI is optional and not supported here */
> + pr_warn("GICv2m: MSI is not supported.\n");
> + return 0;
> + }
Why not pr_info?
Thanks,
Mark.
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