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usb: xhci: guarantee that IMAN register is flushed

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Add read call to guarantee that the write to the IMAN register has
been flushed.

xHCI specification 1.2, section 5.5.2.1, Note:
"Most systems have write buffers that minimize overhead, but this may
 require a read operation to guarantee that the write has been flushed
 from the posted buffer."

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20250515135621.335595-17-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Niklas Neronin 2025-05-15 16:56:13 +03:00 committed by Greg Kroah-Hartman
parent 9f7f74735a
commit f5bce30ad2
2 changed files with 6 additions and 0 deletions
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3
drivers/usb/host/xhci-ring.c
View File

@ -3087,6 +3087,9 @@ static void xhci_clear_interrupt_pending(struct xhci_interrupter *ir)
irq_pending = readl(&ir->ir_set->irq_pending);
irq_pending |= IMAN_IP;
writel(irq_pending, &ir->ir_set->irq_pending);
/* Read operation to guarantee the write has been flushed from posted buffers */
readl(&ir->ir_set->irq_pending);
}
}

3
drivers/usb/host/xhci.c
View File

@ -335,6 +335,8 @@ int xhci_enable_interrupter(struct xhci_interrupter *ir)
iman |= IMAN_IE;
writel(iman, &ir->ir_set->irq_pending);
/* Read operation to guarantee the write has been flushed from posted buffers */
readl(&ir->ir_set->irq_pending);
return 0;
}
@ -350,6 +352,7 @@ int xhci_disable_interrupter(struct xhci_interrupter *ir)
iman &= ~IMAN_IE;
writel(iman, &ir->ir_set->irq_pending);
readl(&ir->ir_set->irq_pending);
return 0;
}