dmaengine: hsu: disable spurious interrupt

[ Upstream commit 035b73b2 ]

On Intel Tangier B0 and Anniedale the interrupt line, disregarding
to have different numbers, is shared between HSU DMA and UART IPs.
Thus on such SoCs we are expecting that IRQ handler is called in
UART driver only. hsu_pci_irq was handling the spurious interrupt
from HSU DMA by returning immediately. This wastes CPU time and
since HSU DMA and HSU UART interrupt occur simultaneously they race
to be handled causing delay to the HSU UART interrupt handling.
Fix this by disabling the interrupt entirely.

Fixes: 4831e0d9 ("serial: 8250_mid: handle interrupt correctly in DMA case")
Signed-off-by: Ferry Toth <ftoth@exalondelft.nl>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20210112223749.97036-1-ftoth@exalondelft.nl


Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>