* Re: [PATCH] AHCI: Clear GHC.IS to prevent unexpectly asserting INTx
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@ 2016-07-20 15:11 ` tj
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From: tj @ 2016-07-20 15:11 UTC (permalink / raw)
To: Pang Raymond; +Cc: ide linux, kernel linux
On Wed, Jul 20, 2016 at 12:13:46PM +0000, Pang Raymond wrote:
>
> Due to PCI subsystem behaviour, unloading AHCI driver will disable
> MSI and enable INTx. When HBA supports MSIx or Multiple MSI, Driver's
> irq handler doesn't clear GHC.IS register. It works well when reading or
> writing data and GHC.IS is always non-zero. But when unloading driver
> (or any other operation which causes disable MSIx and enable INTx), PCI
> subsystem uses config write(Rx04.bit10) to enable INTx. Because
> GHC.IS is non-zero, HBA will falsely assume some port needs interrupt
> service. Then it asserts INTx. To make things worse, when AHCI controller
> shares the same interrupt pin with other PCI device, that PCI device's ISR
> will be called and nobody de-asserts previous INTx.
> This patch clears GHC.IS in ahci_port_stop() even when using MSIx or
> MMSI to prevent this case. It ensures GHC.IS is zero before PCI subsystem
> enables INTx.
>
> Signed-off-by: Raymond Pang <raymond_rule@hotmail.com>
Applied to libata/for-4.8 with minor updates to the comment.
Thanks.
--
tejun
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