On 3/19/21 5:22 PM, Stefano Stabellini wrote: > On Fri, 19 Mar 2021, Konrad Rzeszutek Wilk wrote: >> On Fri, Mar 19, 2021 at 02:07:31PM +0100, Christoph Hellwig wrote: >>> On Thu, Mar 18, 2021 at 09:03:33PM -0700, Florian Fainelli wrote: >>>> #ifdef CONFIG_ARM_LPAE >>>> + if (swiotlb_force == SWIOTLB_FORCE || >>>> + max_pfn > arm_dma_pfn_limit) >>> >>> Does arm_dma_pfn_limit do the right thing even with the weirdest >>> remapping ranges? Maybe a commen here would be useful. >>> >>>> + swiotlb_init(1); >>>> + else >>>> + swiotlb_force = SWIOTLB_NO_FORCE; >>> >>> Konrad: what do you think of setting swiotlb_force to SWIOTLB_NO_FORCE >>> and only switching it to SWIOTLB_NORMAL when swiotlb_init* is called? >>> That kind makes more sense than forcing the callers to do it. >>> >>> While we're at it, I think swiotlb_force should probably be renamed to >>> swiotlb_mode or somethng like that. >> >> swiotlb_mode sounds good. >> >> Also it got me thinking - ARM on Xen at some point was a bit strange, so not >> sure how >> the logic works here, Stefano? > > There is nothing strange in regards to swiotlb_force. swiotlb_force is only > used > in swiotlb-xen map_page to figure out whether: > > - we actually have to use the swiotlb bounce buffer (this is the > swiotlb_xen == SWIOTLB_FORCE case) > - or we can use the provided page directly for dma if other conditions > are met (dma_capable, !range_straddles_page_boundary, ...) > > > I don't think that switching to "swiotlb_mode" would cause any issues. >
Should I toss this in Russell's patch tracker or do you need me to make some changes to the patch? -- Florian
