[PATCH] drm/xe: Make irq enabled flag atomic
Rodrigo Vivi
rodrigo.vivi at intel.com
Wed Dec 11 18:13:49 UTC 2024
On Tue, Dec 10, 2024 at 07:35:06PM +0200, Ilia Levi wrote:
> The irq.enabled flag was protected by a spin lock (irq.lock).
> By making it atomic we no longer need to wait for the spin lock in
> irq handlers. This will become especially useful for MSI-X irq
> handlers to prevent lock contention between different interrupts.
>
> Signed-off-by: Ilia Levi <ilia.levi at intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
pushing soon to drm-xe-next. Thanks for the patch
> ---
> drivers/gpu/drm/xe/display/ext/i915_irq.c | 13 +---------
> drivers/gpu/drm/xe/xe_device_types.h | 2 +-
> drivers/gpu/drm/xe/xe_irq.c | 29 ++++++-----------------
> 3 files changed, 9 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/display/ext/i915_irq.c b/drivers/gpu/drm/xe/display/ext/i915_irq.c
> index a7dbc6554d69..ac4cda2d81c7 100644
> --- a/drivers/gpu/drm/xe/display/ext/i915_irq.c
> +++ b/drivers/gpu/drm/xe/display/ext/i915_irq.c
> @@ -53,18 +53,7 @@ void gen2_irq_init(struct intel_uncore *uncore, struct i915_irq_regs regs,
>
> bool intel_irqs_enabled(struct xe_device *xe)
> {
> - /*
> - * XXX: i915 has a racy handling of the irq.enabled, since it doesn't
> - * lock its transitions. Because of that, the irq.enabled sometimes
> - * is not read with the irq.lock in place.
> - * However, the most critical cases like vblank and page flips are
> - * properly using the locks.
> - * We cannot take the lock in here or run any kind of assert because
> - * of i915 inconsistency.
> - * But at this point the xe irq is better protected against races,
> - * although the full solution would be protecting the i915 side.
> - */
> - return xe->irq.enabled;
> + return atomic_read(&xe->irq.enabled);
> }
>
> void intel_synchronize_irq(struct xe_device *xe)
> diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
> index 1373a222f5a5..ace22e35e769 100644
> --- a/drivers/gpu/drm/xe/xe_device_types.h
> +++ b/drivers/gpu/drm/xe/xe_device_types.h
> @@ -347,7 +347,7 @@ struct xe_device {
> spinlock_t lock;
>
> /** @irq.enabled: interrupts enabled on this device */
> - bool enabled;
> + atomic_t enabled;
> } irq;
>
> /** @ttm: ttm device */
> diff --git a/drivers/gpu/drm/xe/xe_irq.c b/drivers/gpu/drm/xe/xe_irq.c
> index 7bf7201529ac..1c509e66694d 100644
> --- a/drivers/gpu/drm/xe/xe_irq.c
> +++ b/drivers/gpu/drm/xe/xe_irq.c
> @@ -348,12 +348,8 @@ static irqreturn_t xelp_irq_handler(int irq, void *arg)
> unsigned long intr_dw[2];
> u32 identity[32];
>
> - spin_lock(&xe->irq.lock);
> - if (!xe->irq.enabled) {
> - spin_unlock(&xe->irq.lock);
> + if (!atomic_read(&xe->irq.enabled))
> return IRQ_NONE;
> - }
> - spin_unlock(&xe->irq.lock);
>
> master_ctl = xelp_intr_disable(xe);
> if (!master_ctl) {
> @@ -417,12 +413,8 @@ static irqreturn_t dg1_irq_handler(int irq, void *arg)
>
> /* TODO: This really shouldn't be copied+pasted */
>
> - spin_lock(&xe->irq.lock);
> - if (!xe->irq.enabled) {
> - spin_unlock(&xe->irq.lock);
> + if (!atomic_read(&xe->irq.enabled))
> return IRQ_NONE;
> - }
> - spin_unlock(&xe->irq.lock);
>
> master_tile_ctl = dg1_intr_disable(xe);
> if (!master_tile_ctl) {
> @@ -644,12 +636,8 @@ static irqreturn_t vf_mem_irq_handler(int irq, void *arg)
> struct xe_tile *tile;
> unsigned int id;
>
> - spin_lock(&xe->irq.lock);
> - if (!xe->irq.enabled) {
> - spin_unlock(&xe->irq.lock);
> + if (!atomic_read(&xe->irq.enabled))
> return IRQ_NONE;
> - }
> - spin_unlock(&xe->irq.lock);
>
> for_each_tile(tile, xe, id)
> xe_memirq_handler(&tile->memirq);
> @@ -674,10 +662,9 @@ static void irq_uninstall(void *arg)
> struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
> int irq;
>
> - if (!xe->irq.enabled)
> + if (!atomic_xchg(&xe->irq.enabled, 0))
> return;
>
> - xe->irq.enabled = false;
> xe_irq_reset(xe);
>
> irq = pci_irq_vector(pdev, 0);
> @@ -724,7 +711,7 @@ int xe_irq_install(struct xe_device *xe)
> return err;
> }
>
> - xe->irq.enabled = true;
> + atomic_set(&xe->irq.enabled, 1);
>
> xe_irq_postinstall(xe);
>
> @@ -744,9 +731,7 @@ void xe_irq_suspend(struct xe_device *xe)
> {
> int irq = to_pci_dev(xe->drm.dev)->irq;
>
> - spin_lock_irq(&xe->irq.lock);
> - xe->irq.enabled = false; /* no new irqs */
> - spin_unlock_irq(&xe->irq.lock);
> + atomic_set(&xe->irq.enabled, 0); /* no new irqs */
>
> synchronize_irq(irq); /* flush irqs */
> xe_irq_reset(xe); /* turn irqs off */
> @@ -762,7 +747,7 @@ void xe_irq_resume(struct xe_device *xe)
> * 1. no irq will arrive before the postinstall
> * 2. display is not yet resumed
> */
> - xe->irq.enabled = true;
> + atomic_set(&xe->irq.enabled, 1);
> xe_irq_reset(xe);
> xe_irq_postinstall(xe); /* turn irqs on */
>
> --
> 2.43.2
>
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