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thunderbolt: Use shadow copy for ring interrupt mask

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Each time we mask or unmask ring interrupt we do a read-modify-write and
that is not without a cost when on a hot path. We can get rid of that
read by making a shadow copy of the interrupt mask register and using
that in place of a register read.

Assisted-by: LLM
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
This commit is contained in:
Mika Westerberg 2026-08-14 16:55:04 +03:00
parent 85e5f54bb3
commit 26e6e964d5
2 changed files with 36 additions and 21 deletions
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55
drivers/thunderbolt/nhi.c
View File

@ -52,15 +52,28 @@ static int ring_interrupt_index(const struct tb_ring *ring)
static void nhi_mask_interrupt(struct tb_nhi *nhi, u32 mask, int reg_index)
{
int offset = reg_index * 4;
u32 val;
if (nhi->quirks & QUIRK_AUTO_CLEAR_INT) {
u32 val;
/* Use shadow copy instead of reading the register */
val = nhi->interrupt_mask[reg_index] & ~mask;
nhi->interrupt_mask[reg_index] = val;
val = ioread32(nhi->iobase + REG_RING_INTERRUPT_BASE + offset);
iowrite32(val & ~mask, nhi->iobase + REG_RING_INTERRUPT_BASE + offset);
} else {
if (nhi->quirks & QUIRK_AUTO_CLEAR_INT)
iowrite32(val, nhi->iobase + REG_RING_INTERRUPT_BASE + offset);
else
iowrite32(mask, nhi->iobase + REG_RING_INTERRUPT_MASK_CLEAR_BASE + offset);
}
}
static void nhi_unmask_interrupt(struct tb_nhi *nhi, u32 mask, int reg_index)
{
int offset = reg_index * 4;
u32 val;
/* Use shadow copy instead of reading the register */
val = nhi->interrupt_mask[reg_index] | mask;
nhi->interrupt_mask[reg_index] = val;
iowrite32(val, nhi->iobase + REG_RING_INTERRUPT_BASE + offset);
}
static void nhi_clear_interrupt(struct tb_nhi *nhi, int reg_index)
@ -128,7 +141,7 @@ static void ring_interrupt_active(struct tb_ring *ring, bool active)
ring->vector * 4);
}
old = ioread32(ring->nhi->iobase + reg);
old = ring->nhi->interrupt_mask[reg_index];
if (active)
new = old | mask;
else
@ -140,10 +153,10 @@ static void ring_interrupt_active(struct tb_ring *ring, bool active)
if (new == old) {
/*
* Rings that are polled mask the interrupt using while
* the completions are being advanced (see
* __ring_interrupt()) so for those it can already be
* disabled by the time the ring is stopped.
* Rings that are polled mask the interrupt while the
* completions are being advanced (see __ring_interrupt())
* so for those it can already be disabled by the time
* the ring is stopped.
*/
if (active || !ring->start_poll)
dev_WARN(ring->nhi->dev,
@ -153,7 +166,7 @@ static void ring_interrupt_active(struct tb_ring *ring, bool active)
}
if (active)
iowrite32(new, ring->nhi->iobase + reg);
nhi_unmask_interrupt(ring->nhi, mask, reg_index);
else
nhi_mask_interrupt(ring->nhi, mask, reg_index);
}
@ -436,17 +449,14 @@ EXPORT_SYMBOL_GPL(tb_ring_poll);
static void __ring_interrupt_mask(struct tb_ring *ring, bool mask)
{
int idx = ring_interrupt_index(ring);
int reg = REG_RING_INTERRUPT_BASE + idx / 32 * 4;
int bit = idx % 32;
u32 val;
int interrupt_index = ring_interrupt_index(ring);
int reg_index = interrupt_index / 32;
int interrupt_bit = interrupt_index % 32;
val = ioread32(ring->nhi->iobase + reg);
if (mask)
val &= ~BIT(bit);
nhi_mask_interrupt(ring->nhi, BIT(interrupt_bit), reg_index);
else
val |= BIT(bit);
iowrite32(val, ring->nhi->iobase + reg);
nhi_unmask_interrupt(ring->nhi, BIT(interrupt_bit), reg_index);
}
/* Both @nhi->lock and @ring->lock should be held */
@ -1310,7 +1320,10 @@ int nhi_probe(struct tb_nhi *nhi)
sizeof(*nhi->tx_rings), GFP_KERNEL);
nhi->rx_rings = devm_kcalloc(dev, nhi->hop_count,
sizeof(*nhi->rx_rings), GFP_KERNEL);
if (!nhi->tx_rings || !nhi->rx_rings)
nhi->interrupt_mask = devm_kcalloc(dev, RING_INTERRUPT_REG_COUNT(nhi),
sizeof(*nhi->interrupt_mask),
GFP_KERNEL);
if (!nhi->tx_rings || !nhi->rx_rings || !nhi->interrupt_mask)
return -ENOMEM;
nhi_reset(nhi);

2
include/linux/thunderbolt.h
View File

@ -506,6 +506,7 @@ void tb_service_properties_changed(struct tb_service *svc);
* @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
* @interrupt_mask: Shadow copy of the ring interrupt mask register
* @going_away: The host controller device is about to disappear so when
* this flag is set, avoid touching the hardware anymore.
* @iommu_dma_protection: An IOMMU will isolate external-facing ports.
@ -527,6 +528,7 @@ struct tb_nhi {
void __iomem *iobase;
struct tb_ring **tx_rings;
struct tb_ring **rx_rings;
u32 *interrupt_mask;
bool going_away;
bool iommu_dma_protection;
struct work_struct interrupt_work;