Re: [PATCH v2] swiotlb: introduce Kconfig option for compile-time default pool size
Marek Szyprowski <[email protected]>
| Newsgroups | gmane.linux.kernel,gmane.linux.documentation |
|---|---|
| Message-ID | <[email protected]> |
On 02.07.2026 16:09, [email protected] wrote: > From: Jagadeesh Pagadala <[email protected]> > > The SWIOTLB bounce buffer pool size is hardcoded at 64 MB via > IO_TLB_DEFAULT_SIZE with no compile-time knob to adjust it. On > memory-constrained embedded or mobile platforms equipped with a > hardware IOMMU (e.g., ARM SMMU) covering most DMA-capable devices, > reserving 64 MB at boot is unnecessarily wasteful — the SWIOTLB is > only exercised for devices that bypass the IOMMU or have restricted > DMA address ranges. > > Introduce CONFIG_SWIOTLB_DEFAULT_SIZE_MB, an integer Kconfig option > (range 1–64 MB, default 64) that allows platforms to set a smaller > compile-time default. IO_TLB_DEFAULT_SIZE is updated to derive from > this value when CONFIG_SWIOTLB is enabled, preserving the existing > 64 MB default when the option is not configured. > > The runtime "swiotlb=<nslabs>" kernel parameter override remains > fully supported and takes precedence over the compile-time default. > > Signed-off-by: Jagadeesh Pagadala <[email protected]> > Signed-off-by: Bibek Kumar Patro <[email protected]> Applied to dma-mapping-for-next, thanks! Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland