path: root/stand/efi/fdt
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authorWarner Losh <imp@FreeBSD.org>2019-09-04 20:08:36 +0000
committerWarner Losh <imp@FreeBSD.org>2019-09-04 20:08:36 +0000
commitf93b7f954e96d5162007561ea3ddc1443468d912 (patch)
tree8f672da7f1e16731d81d3bd8aa22902e9389b21b /stand/efi/fdt
parentc07d4a0a681c7db4fd30dd27a3b949f1820e63c3 (diff)
Support doorbell strides != 0.
The NVMe standard (1.4) states >>> 8.6 Doorbell Stride for Software Emulation >>> The doorbell stride,...is useful in software emulation of an NVM >>> Express controller. ... For hardware implementations of the NVM >>> Express interface, the expected doorbell stride value is 0h. However, hardware in the wild exists with a doorbell stride of 1 (meaning 8 byte separation). This change supports that hardware, as well as software emulators as envisioned in Section 8.6. Since this is the fast path, care has been taken to make this computation efficient. The bit of math to compute an offset for each is replaced by a memory load from cache of a pre-computed value. MFC After: 3 days Reviewed by: scottl@ Differential Revision: https://reviews.freebsd.org/D21514
Notes: svn path=/head/; revision=351828
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