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irqchip/gic: Atomically update affinity

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The GIC driver uses a RMW sequence to update the affinity, and
relies on the gic_lock_irqsave/gic_unlock_irqrestore sequences
to update it atomically.

But these sequences only expand into anything meaningful if
the BL_SWITCHER option is selected, which almost never happens.

It also turns out that using a RMW and locks is just as silly,
as the GIC distributor supports byte accesses for the GICD_TARGETRn
registers, which when used make the update atomic by definition.

Drop the terminally broken code and replace it by a byte write.

Fixes: 04c8b0f82c ("irqchip/gic: Make locking a BL_SWITCHER only feature")
Cc: stable@vger.kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Marc Zyngier 2020-06-21 14:43:15 +01:00
parent 559fe74ba6
commit 005c34ae4b
1 changed files with 3 additions and 11 deletions
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14
drivers/irqchip/irq-gic.c
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@ -329,10 +329,8 @@ static int gic_irq_set_vcpu_affinity(struct irq_data *d, void *vcpu)
static int gic_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
bool force)
{
void __iomem *reg = gic_dist_base(d) + GIC_DIST_TARGET + (gic_irq(d) & ~3);
unsigned int cpu, shift = (gic_irq(d) % 4) * 8;
u32 val, mask, bit;
unsigned long flags;
void __iomem *reg = gic_dist_base(d) + GIC_DIST_TARGET + gic_irq(d);
unsigned int cpu;
if (!force)
cpu = cpumask_any_and(mask_val, cpu_online_mask);
@ -342,13 +340,7 @@ static int gic_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
if (cpu >= NR_GIC_CPU_IF || cpu >= nr_cpu_ids)
return -EINVAL;
gic_lock_irqsave(flags);
mask = 0xff << shift;
bit = gic_cpu_map[cpu] << shift;
val = readl_relaxed(reg) & ~mask;
writel_relaxed(val | bit, reg);
gic_unlock_irqrestore(flags);
writeb_relaxed(gic_cpu_map[cpu], reg);
irq_data_update_effective_affinity(d, cpumask_of(cpu));
return IRQ_SET_MASK_OK_DONE;