RE: [PATCH] iommu/arm-smmu-v3: remove the approach of MSI polling for CMD SYNC

2020-07-20 Thread Song Bao Hua (Barry Song)
> -Original Message- > From: Song Bao Hua (Barry Song) > Sent: Friday, July 17, 2020 9:06 PM > To: 'Robin Murphy' ; w...@kernel.org; > j...@8bytes.org > Cc: linux-ker...@vger.kernel.org; Linuxarm ; > linux-arm-ker...@lists.infradead.org; iommu@lists.linux-foundation.org; > Zengtao (B)

RE: [PATCH] iommu/arm-smmu-v3: remove the approach of MSI polling for CMD SYNC

2020-07-17 Thread Song Bao Hua (Barry Song)
> -Original Message- > From: Robin Murphy [mailto:robin.mur...@arm.com] > Sent: Friday, July 17, 2020 8:55 PM > To: Song Bao Hua (Barry Song) ; w...@kernel.org; > j...@8bytes.org > Cc: linux-ker...@vger.kernel.org; Linuxarm ; > linux-arm-ker...@lists.infradead.org;

Re: [PATCH] iommu/arm-smmu-v3: remove the approach of MSI polling for CMD SYNC

2020-07-17 Thread Robin Murphy
On 2020-07-17 00:07, Barry Song wrote: Before commit 587e6c10a7ce ("iommu/arm-smmu-v3: Reduce contention during command-queue insertion"), msi polling perhaps performed better since it could run outside the spin_lock_irqsave() while the code polling cons reg was running in the lock. But after