[DragonFlyBSD - Bug #3448] (New) iwm(4): allow 36-bit DMA for the RX/TX data buffers

[sigttou]

Issue #3448 has been reported by sigttou.

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Bug #3448: iwm(4): allow 36-bit DMA for the RX/TX data buffers
http://bugs.dragonflybsd.org/issues/3448

* Author: sigttou
* Status: New
* Priority: Normal
* Category: Driver
* Target version: 6.6
* Start date: 2026-10-16
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iwm(4) creates its RX and TX data-buffer DMA tags with @BUS_SPACE_MAXADDR_32BIT at . On hosts with more than 4 GB of RAM essentially all Wi-Fi traffic is bounced through busdma, and the bounce zone can exhaust under load: TX frames are dropped (@can't map mbuf@) and RX replenishment fails.

Raise only the two data-buffer tags to @0xfffffffff@ (36-bit), the limit Linux iwlwifi uses for non-gen2 devices (7000/8000/9000: @tfd.addr_size = 36@; gen2 22000+ uses 64-bit). The hardware paths already support it: 9000-series MQ RX free descriptors are written as full 64-bit addresses, the legacy RX descriptor stores @addr >> 8@, and TX TFD buffer addresses carry bits @[35:32]@ via the existing @iwm_get_dma_hi_addr()@ handling.

---Files--------------------------------
0002-iwm-4-allow-36-bit-DMA-for-the-RX-TX-data-buffers.patch (1.85 KB)


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