Re: [RFT PATCH v3 12/27] of/address: Add infrastructure to declare MMIO as non-posted
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From: Hector Martin <hidden>
Date: 2021-03-05 17:20:15
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linux-arm-kernel, linux-devicetree, linux-doc, linux-samsung-soc, linux-serial, lkml
On 06/03/2021 01.43, Arnd Bergmann wrote:
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- setting ioremap() on PCI buses non-posted only makes them only slower but not more reliable, because the non-posted flag on the bus is discarded by the PCI host bridge.
Note that this doesn't work here *anyway*. The fabric is picky in both directions: thou shalt use nGnRnE for on-SoC MMIO and nGnRE for PCIe windows, or else, SError. Since these devices can support *any* PCI device via Thunderbolt, making PCI drivers be the oddball ones needing special APIs would mean hundreds of changes needed - the vast majority of PCI drivers in the kernel use plain ioremap variants that don't have any flags to look at. -- Hector Martin (marcan@marcan.st) Public Key: https://mrcn.st/pub