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IPMMU hardware on R-Car Gen3 and RZ/G2 is simple. Each bus-master device like eMMC host and PCIe controllers has a micro-TLB of The IPMMU, and after enabled it, all transactions of the device are under the IPMMU. eMMC host ---(micro-TLB of eMMC)--- IPMMU cache --- IPMMU main PCIe --------(micro-TLB of PCIe)--- IPMMU cache --- IPMMU main Now this IPMMU driver allows eMMC host, and it is safe to use the IPMMU. So, we can assume that it is safe to use the IPMMU from PCIe devices too, because all PCIe devices transactions will go to the micro-TLB of PCIe. So, add a new condition whether the device is a PCIe device or not in the ipmmu_device_is_allowed() which will be called if the PCIe host controller has iommu-map property. This can improve CPU load because the PCIe controllers only have a capability for lower 32-bit memory area so that this can avoid using swiotlb. Note that IPMMU on R-Car Gen4 is different than R-Car Gen3 and RZ/G2's one, especially OS-ID. But, for now, the IPMMU driver takes care of OS-ID 0 only. In other words, all PCIe devices will go to the micro-TLB of PCIe. Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be> Link: https://lore.kernel.org/r/20230728014659.411751-1-yoshihiro.shimoda.uh@renesas.com Signed-off-by: Joerg Roedel <jroedel@suse.de>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.