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lib: sbi: Allow relaxed MMIO writes in device ipi_send() callback

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Currently, we have a smp_wmb() between atomic_raw_set_bit() and
ipi_send() device callback whereas the MMIO writes done by the
device ipi_send() callback will also include a barrier.

We can avoid unnecessary/redundant barriers described above by
allowing relaxed MMIO writes in device ipi_send() callback. To
achieve this, we simply use  wmb() instead of smp_wmb() before
calling device ipi_send().

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reported-by: Bo Gan <ganboing@gmail.com>
This commit is contained in:
Anup Patel 2023-11-21 14:49:42 +05:30 • committed by Anup Patel
parent 791704cd09
commit f520256d03
3 changed files with 14 additions and 7 deletions
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15
lib/sbi/sbi_ipi.c
View file

@ -67,14 +67,12 @@ static int sbi_ipi_send(struct sbi_scratch *scratch, u32 remote_hartindex,
* trigger the interrupt
*/
atomic_raw_set_bit(event, &ipi_data->ipi_type);
smp_wmb();
if (ipi_dev && ipi_dev->ipi_send)
ipi_dev->ipi_send(remote_hartindex);
ret = sbi_ipi_raw_send(remote_hartindex);
sbi_pmu_ctr_incr_fw(SBI_PMU_FW_IPI_SENT);
return 0;
return ret;
}
static int sbi_ipi_sync(struct sbi_scratch *scratch, u32 event)
@ -243,6 +241,15 @@ int sbi_ipi_raw_send(u32 hartindex)
if (!ipi_dev || !ipi_dev->ipi_send)
return SBI_EINVAL;
/*
* Ensure that memory or MMIO writes done before
* this function are not observed after the memory
* or MMIO writes done by the ipi_send() device
* callback. This also allows the ipi_send() device
* callback to use relaxed MMIO writes.
*/
wmb();
ipi_dev->ipi_send(hartindex);
return 0;
}

2
lib/utils/ipi/aclint_mswi.c
View file

@ -41,7 +41,7 @@ static void mswi_ipi_send(u32 hart_index)
/* Set ACLINT IPI */
msip = (void *)mswi->addr;
writel(1, &msip[sbi_hartindex_to_hartid(hart_index) -
writel_relaxed(1, &msip[sbi_hartindex_to_hartid(hart_index) -
mswi->first_hartid]);
}

4
lib/utils/irqchip/imsic.c
View file

@ -186,8 +186,8 @@ static void imsic_ipi_send(u32 hart_index)
}
if (regs->size && (reloff < regs->size))
writel(IMSIC_IPI_ID,
(void *)(regs->addr + reloff + IMSIC_MMIO_PAGE_LE));
writel_relaxed(IMSIC_IPI_ID,
(void *)(regs->addr + reloff + IMSIC_MMIO_PAGE_LE));
}
static struct sbi_ipi_device imsic_ipi_device = {