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SubjectRe: [PATCH 04/24] thunderbolt: Add MSI-X support
On Thu, May 18, 2017 at 4:38 PM, Mika Westerberg
<mika.westerberg@linux.intel.com> wrote:
> Intel Thunderbolt controllers support up to 16 MSI-X vectors. Using
Is that true for all generations? If so can we remove the legacy path?

> MSI-X is preferred over MSI or legacy interrupt and may bring additional
> performance because there is no need to check the status registers which
> interrupt was triggered.
>
> While there we convert comments in structs tb_ring and tb_nhi to follow
> kernel-doc format more closely.
>
> This code is based on the work done by Amir Levy and Michael Jamet.
>
> Signed-off-by: Michael Jamet <michael.jamet@intel.com>
> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> Reviewed-by: Yehezkel Bernat <yehezkel.bernat@intel.com>
> ---
> drivers/thunderbolt/ctl.c | 4 +-
> drivers/thunderbolt/nhi.c | 159 ++++++++++++++++++++++++++++++++++++-----
> drivers/thunderbolt/nhi.h | 56 +++++++++++----
> drivers/thunderbolt/nhi_regs.h | 9 +++
> 4 files changed, 196 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/thunderbolt/ctl.c b/drivers/thunderbolt/ctl.c
> index 1031d97407a8..889a32dd21e7 100644
> --- a/drivers/thunderbolt/ctl.c
> +++ b/drivers/thunderbolt/ctl.c
> @@ -488,11 +488,11 @@ struct tb_ctl *tb_ctl_alloc(struct tb_nhi *nhi, hotplug_cb cb, void *cb_data)
> if (!ctl->frame_pool)
> goto err;
>
> - ctl->tx = ring_alloc_tx(nhi, 0, 10);
> + ctl->tx = ring_alloc_tx(nhi, 0, 10, RING_FLAG_NO_SUSPEND);
> if (!ctl->tx)
> goto err;
>
> - ctl->rx = ring_alloc_rx(nhi, 0, 10);
> + ctl->rx = ring_alloc_rx(nhi, 0, 10, RING_FLAG_NO_SUSPEND);
> if (!ctl->rx)
> goto err;
>
> diff --git a/drivers/thunderbolt/nhi.c b/drivers/thunderbolt/nhi.c
> index a8c20413dbda..17f3b1bdb7da 100644
> --- a/drivers/thunderbolt/nhi.c
> +++ b/drivers/thunderbolt/nhi.c
> @@ -21,6 +21,12 @@
>
> #define RING_TYPE(ring) ((ring)->is_tx ? "TX ring" : "RX ring")
>
> +/*
> + * Minimal number of vectors when we use MSI-X. Two for control channel
> + * Rx/Tx and the rest four are for cross domain DMA paths.
> + */
> +#define MSIX_MIN_VECS 6
> +#define MSIX_MAX_VECS 16
>
> static int ring_interrupt_index(struct tb_ring *ring)
> {
> @@ -239,8 +245,82 @@ int __ring_enqueue(struct tb_ring *ring, struct ring_frame *frame)
> return ret;
> }
>
> +static irqreturn_t ring_msix(int irq, void *data)
> +{
> + struct tb_ring *ring = data;
> +
> + schedule_work(&ring->work);
> + return IRQ_HANDLED;
> +}
> +
> +static void ring_map_unmap_msix(struct tb_ring *ring, bool map)
> +{
This function does the same as ring_interrupt_active just for msix,
right? Can we rename one (or both) to express that?
For example rename ring_interrput_active -> ring_map_unmap_msi. Or
just roll this one into ring_interrupt_active and do the right thing
internally.

> + u32 step, shift, ivr, misc;
> + int index;
> +
> + if (ring->irq <= 0)
> + return;
> +
> + if (ring->is_tx)
> + index = ring->hop;
> + else
> + index = ring->hop + ring->nhi->hop_count;
> +
> + /*
> + * Ask the hardware to clear interrupt status bits automatically
> + * since we already know which interrupt was triggered.
> + */
> + misc = ioread32(ring->nhi->iobase + REG_DMA_MISC);
> + if (!(misc & REG_DMA_MISC_INT_AUTO_CLEAR)) {
> + misc |= REG_DMA_MISC_INT_AUTO_CLEAR;
> + iowrite32(misc, ring->nhi->iobase + REG_DMA_MISC);
> + }
> +
> + step = index / REG_INT_VEC_ALLOC_REGS * REG_INT_VEC_ALLOC_BITS;
> + shift = index % REG_INT_VEC_ALLOC_REGS * REG_INT_VEC_ALLOC_BITS;
> + ivr = ioread32(ring->nhi->iobase + REG_INT_VEC_ALLOC_BASE + step);
> + ivr &= ~(REG_INT_VEC_ALLOC_MASK << shift);
> + if (map)
> + ivr |= ring->vector << shift;
> + iowrite32(ivr, ring->nhi->iobase + REG_INT_VEC_ALLOC_BASE + step);
> +}
> +
> +static int ring_request_msix(struct tb_ring *ring, bool no_suspend)
> +{
> + struct tb_nhi *nhi = ring->nhi;
> + unsigned long irqflags;
> + int ret;
> +
> + if (!nhi->pdev->msix_enabled)
> + return 0;
> +
> + ret = ida_simple_get(&nhi->msix_ida, 0, MSIX_MAX_VECS, GFP_KERNEL);
> + if (ret < 0)
> + return ret;
> +
> + ring->vector = ret;
> +
> + ring->irq = pci_irq_vector(ring->nhi->pdev, ring->vector);
> + if (ring->irq < 0)
> + return ring->irq;
> +
> + irqflags = no_suspend ? IRQF_NO_SUSPEND : 0;
> + return request_irq(ring->irq, ring_msix, irqflags, "thunderbolt", ring);
> +}
> +
> +static void ring_release_msix(struct tb_ring *ring)
> +{
> + if (ring->irq <= 0)
> + return;
> +
> + free_irq(ring->irq, ring);
> + ida_simple_remove(&ring->nhi->msix_ida, ring->vector);
> + ring->vector = 0;
> + ring->irq = 0;
> +}
> +
> static struct tb_ring *ring_alloc(struct tb_nhi *nhi, u32 hop, int size,
> - bool transmit)
> + bool transmit, unsigned int flags)
> {
> struct tb_ring *ring = NULL;
> dev_info(&nhi->pdev->dev, "allocating %s ring %d of size %d\n",
> @@ -271,9 +351,14 @@ static struct tb_ring *ring_alloc(struct tb_nhi *nhi, u32 hop, int size,
> ring->hop = hop;
> ring->is_tx = transmit;
> ring->size = size;
> + ring->flags = flags;
> ring->head = 0;
> ring->tail = 0;
> ring->running = false;
> +
> + if (ring_request_msix(ring, flags & RING_FLAG_NO_SUSPEND))
> + goto err;
> +
> ring->descriptors = dma_alloc_coherent(&ring->nhi->pdev->dev,
> size * sizeof(*ring->descriptors),
> &ring->descriptors_dma, GFP_KERNEL | __GFP_ZERO);
> @@ -295,14 +380,16 @@ static struct tb_ring *ring_alloc(struct tb_nhi *nhi, u32 hop, int size,
> return NULL;
> }
>
> -struct tb_ring *ring_alloc_tx(struct tb_nhi *nhi, int hop, int size)
> +struct tb_ring *ring_alloc_tx(struct tb_nhi *nhi, int hop, int size,
> + unsigned int flags)
> {
> - return ring_alloc(nhi, hop, size, true);
> + return ring_alloc(nhi, hop, size, true, flags);
> }
>
> -struct tb_ring *ring_alloc_rx(struct tb_nhi *nhi, int hop, int size)
> +struct tb_ring *ring_alloc_rx(struct tb_nhi *nhi, int hop, int size,
> + unsigned int flags)
> {
> - return ring_alloc(nhi, hop, size, false);
> + return ring_alloc(nhi, hop, size, false, flags);
> }
>
> /**
> @@ -334,6 +421,7 @@ void ring_start(struct tb_ring *ring)
> ring_iowrite32options(ring,
> RING_FLAG_ENABLE | RING_FLAG_RAW, 0);
> }
> + ring_map_unmap_msix(ring, true);
> ring_interrupt_active(ring, true);
> ring->running = true;
> err:
> @@ -366,6 +454,7 @@ void ring_stop(struct tb_ring *ring)
> goto err;
> }
> ring_interrupt_active(ring, false);
> + ring_map_unmap_msix(ring, false);
>
> ring_iowrite32options(ring, 0, 0);
> ring_iowrite64desc(ring, 0, 0);
> @@ -413,6 +502,8 @@ void ring_free(struct tb_ring *ring)
> RING_TYPE(ring), ring->hop);
> }
>
> + ring_release_msix(ring);
> +
> dma_free_coherent(&ring->nhi->pdev->dev,
> ring->size * sizeof(*ring->descriptors),
> ring->descriptors, ring->descriptors_dma);
There is a comment a couple lines below that states that ring->work is
only scheduled by nhi_interrupt_work and ring_stop. Please add
ring_msix to the list.

> @@ -528,9 +619,51 @@ static void nhi_shutdown(struct tb_nhi *nhi)
> * We have to release the irq before calling flush_work. Otherwise an
> * already executing IRQ handler could call schedule_work again.
> */
> - devm_free_irq(&nhi->pdev->dev, nhi->pdev->irq, nhi);
> + if (!nhi->pdev->msix_enabled)
> + devm_free_irq(&nhi->pdev->dev, nhi->pdev->irq, nhi);
> flush_work(&nhi->interrupt_work);
> mutex_destroy(&nhi->lock);
> + ida_destroy(&nhi->msix_ida);
> +}
> +
> +static int nhi_init_msi(struct tb_nhi *nhi)
> +{
> + struct pci_dev *pdev = nhi->pdev;
> + int res, irq, nvec;
> +
> + /* In case someone left them on. */
> + nhi_disable_interrupts(nhi);
> +
> + ida_init(&nhi->msix_ida);
> +
> + /*
> + * The NHI has 16 MSI-X vectors or a single MSI. We first try to
> + * get all MSI-X vectors and if we succeed, each ring will have
> + * one MSI-X. If for some reason that does not work out, we
> + * fallback to a single MSI.
> + */
> + nvec = pci_alloc_irq_vectors(pdev, MSIX_MIN_VECS, MSIX_MAX_VECS,
> + PCI_IRQ_MSIX);
> + if (nvec < 0) {
> + nvec = pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_MSI);
> + if (nvec < 0)
> + return nvec;
> +
> + INIT_WORK(&nhi->interrupt_work, nhi_interrupt_work);
As far as I can see INIT_WORK is only called here in the fallback
case. But flush_work is still called unconditionally in nhi_shutdown.
> +
> + irq = pci_irq_vector(nhi->pdev, 0);
> + if (irq < 0)
> + return irq;
> +
> + res = devm_request_irq(&pdev->dev, irq, nhi_msi,
> + IRQF_NO_SUSPEND, "thunderbolt", nhi);
> + if (res) {
> + dev_err(&pdev->dev, "request_irq failed, aborting\n");
> + return res;
> + }
> + }
> +
> + return 0;
> }
>
> static int nhi_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> @@ -545,12 +678,6 @@ static int nhi_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> return res;
> }
>
> - res = pci_enable_msi(pdev);
> - if (res) {
> - dev_err(&pdev->dev, "cannot enable MSI, aborting\n");
> - return res;
> - }
> -
> res = pcim_iomap_regions(pdev, 1 << 0, "thunderbolt");
> if (res) {
> dev_err(&pdev->dev, "cannot obtain PCI resources, aborting\n");
> @@ -568,7 +695,6 @@ static int nhi_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> if (nhi->hop_count != 12 && nhi->hop_count != 32)
> dev_warn(&pdev->dev, "unexpected hop count: %d\n",
> nhi->hop_count);
> - INIT_WORK(&nhi->interrupt_work, nhi_interrupt_work);
>
> nhi->tx_rings = devm_kcalloc(&pdev->dev, nhi->hop_count,
> sizeof(*nhi->tx_rings), GFP_KERNEL);
> @@ -577,12 +703,9 @@ static int nhi_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> if (!nhi->tx_rings || !nhi->rx_rings)
> return -ENOMEM;
>
> - nhi_disable_interrupts(nhi); /* In case someone left them on. */
> - res = devm_request_irq(&pdev->dev, pdev->irq, nhi_msi,
> - IRQF_NO_SUSPEND, /* must work during _noirq */
> - "thunderbolt", nhi);
> + res = nhi_init_msi(nhi);
> if (res) {
> - dev_err(&pdev->dev, "request_irq failed, aborting\n");
> + dev_err(&pdev->dev, "cannot enable MSI, aborting\n");
> return res;
> }
>
> diff --git a/drivers/thunderbolt/nhi.h b/drivers/thunderbolt/nhi.h
> index 317242939b31..630f44140530 100644
> --- a/drivers/thunderbolt/nhi.h
> +++ b/drivers/thunderbolt/nhi.h
> @@ -7,45 +7,75 @@
> #ifndef DSL3510_H_
> #define DSL3510_H_
>
> +#include <linux/idr.h>
> #include <linux/mutex.h>
> #include <linux/workqueue.h>
>
> /**
> * struct tb_nhi - thunderbolt native host interface
> + * @lock: Must be held during ring creation/destruction. Is acquired by
> + * interrupt_work when dispatching interrupts to individual rings.
> + * @pdev: Pointer to the PCI device
> + * @iobase: MMIO space of the NHI
> + * @tx_rings: All Tx rings available on this host controller
> + * @rx_rings: All Rx rings available on this host controller
> + * @msix_ida: Used to allocate MSI-X vectors for rings
> + * @interrupt_work: Work scheduled to handle ring interrupt when no
> + * MSI-X is used.
> + * @hop_count: Number of rings (end point hops) supported by NHI.
> */
> struct tb_nhi {
> - struct mutex lock; /*
> - * Must be held during ring creation/destruction.
> - * Is acquired by interrupt_work when dispatching
> - * interrupts to individual rings.
> - **/
> + struct mutex lock;
> struct pci_dev *pdev;
> void __iomem *iobase;
> struct tb_ring **tx_rings;
> struct tb_ring **rx_rings;
> + struct ida msix_ida;
> struct work_struct interrupt_work;
> - u32 hop_count; /* Number of rings (end point hops) supported by NHI. */
> + u32 hop_count;
> };
>
> /**
> * struct tb_ring - thunderbolt TX or RX ring associated with a NHI
> + * @lock: Lock serializing actions to this ring. Must be acquired after
> + * nhi->lock.
> + * @nhi: Pointer to the native host controller interface
> + * @size: Size of the ring
> + * @hop: Hop (DMA channel) associated with this ring
> + * @head: Head of the ring (write next descriptor here)
> + * @tail: Tail of the ring (complete next descriptor here)
> + * @descriptors: Allocated descriptors for this ring
> + * @queue: Queue holding frames to be transferred over this ring
> + * @in_flight: Queue holding frames that are currently in flight
> + * @work: Interrupt work structure
> + * @is_tx: Is the ring Tx or Rx
> + * @running: Is the ring running
> + * @irq: MSI-X irq number if the ring uses MSI-X. %0 otherwise.
> + * @vector: MSI-X vector number the ring uses (only set if @irq is > 0)
> + * @flags: Ring specific flags
> */
> struct tb_ring {
> - struct mutex lock; /* must be acquired after nhi->lock */
> + struct mutex lock;
> struct tb_nhi *nhi;
> int size;
> int hop;
> - int head; /* write next descriptor here */
> - int tail; /* complete next descriptor here */
> + int head;
> + int tail;
> struct ring_desc *descriptors;
> dma_addr_t descriptors_dma;
> struct list_head queue;
> struct list_head in_flight;
> struct work_struct work;
> - bool is_tx:1; /* rx otherwise */
> + bool is_tx:1;
> bool running:1;
> + int irq;
> + u8 vector;
> + unsigned int flags;
> };
>
> +/* Leave ring interrupt enabled on suspend */
> +#define RING_FLAG_NO_SUSPEND BIT(0)
> +
> struct ring_frame;
> typedef void (*ring_cb)(struct tb_ring*, struct ring_frame*, bool canceled);
>
> @@ -64,8 +94,10 @@ struct ring_frame {
>
> #define TB_FRAME_SIZE 0x100 /* minimum size for ring_rx */
>
> -struct tb_ring *ring_alloc_tx(struct tb_nhi *nhi, int hop, int size);
> -struct tb_ring *ring_alloc_rx(struct tb_nhi *nhi, int hop, int size);
> +struct tb_ring *ring_alloc_tx(struct tb_nhi *nhi, int hop, int size,
> + unsigned int flags);
> +struct tb_ring *ring_alloc_rx(struct tb_nhi *nhi, int hop, int size,
> + unsigned int flags);
> void ring_start(struct tb_ring *ring);
> void ring_stop(struct tb_ring *ring);
> void ring_free(struct tb_ring *ring);
> diff --git a/drivers/thunderbolt/nhi_regs.h b/drivers/thunderbolt/nhi_regs.h
> index 75cf0691e6c5..48b98d3c7e6a 100644
> --- a/drivers/thunderbolt/nhi_regs.h
> +++ b/drivers/thunderbolt/nhi_regs.h
> @@ -95,7 +95,16 @@ struct ring_desc {
> #define REG_RING_INTERRUPT_BASE 0x38200
> #define RING_INTERRUPT_REG_COUNT(nhi) ((31 + 2 * nhi->hop_count) / 32)
>
> +/* Interrupt Vector Allocation */
> +#define REG_INT_VEC_ALLOC_BASE 0x38c40
> +#define REG_INT_VEC_ALLOC_BITS 4
> +#define REG_INT_VEC_ALLOC_MASK GENMASK(3, 0)
> +#define REG_INT_VEC_ALLOC_REGS (32 / REG_INT_VEC_ALLOC_BITS)
> +
> /* The last 11 bits contain the number of hops supported by the NHI port. */
> #define REG_HOP_COUNT 0x39640
>
> +#define REG_DMA_MISC 0x39864
> +#define REG_DMA_MISC_INT_AUTO_CLEAR BIT(2)
> +
> #endif
> --
> 2.11.0
>

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