1c5d909f88
This commit adds support for DMA RX in slave mode while using the new register set in the AST2600 and AST1030. This patch also pretty much assumes packet mode is enabled, I'm not sure if this will work in DMA step mode. This is particularly useful for testing IPMB exchanges between Zephyr and external devices, which requires multi-master I2C support and DMA in the new register mode, because the Zephyr drivers from Aspeed use DMA in the new mode by default. The Zephyr drivers are also using packet mode. The typical sequence of events for receiving data in DMA slave + packet mode is that the Zephyr firmware will configure the slave address register with an address to receive on and configure the bus's function control register to enable master mode and slave mode simultaneously at startup, before any transfers are initiated. RX DMA is enabled in the slave mode command register, and the slave RX DMA buffer address and slave RX DMA buffer length are set. TX DMA is not covered in this patch. When the Aspeed I2C controller receives data from some other I2C master, it will reset the I2CS_DMA_LEN RX_LEN value to zero, then buffer incoming data in the RX DMA buffer while incrementing the I2CC_DMA_ADDR address counter and decrementing the I2CC_DMA_LEN counter. It will also update the I2CS_DMA_LEN RX_LEN value along the way. Once all the data has been received, the bus controller will raise an interrupt indicating a packet command was completed, the slave address matched, a normal stop condition was seen, and the transfer was an RX operation. If the master sent a NACK instead of a normal stop condition, or the transfer timed out, then a slightly different set of interrupt status values would be set. Those conditions are not handled in this commit. The Zephyr firmware then collects data from the RX DMA buffer and clears the status register by writing the PKT_MODE_EN bit to the status register. In packet mode, clearing the packet mode interrupt enable bit also clears most of the other interrupt bits automatically (except for a few bits above it). Note: if the master transmit or receive functions were in use simultaneously with the slave mode receive functionality, then the master mode functions may have raised the interrupt line for the bus before the DMA slave transfer is complete. It's important to have the slave's interrupt status register clear throughout the receive operation, and if the slave attempts to raise the interrupt before the master interrupt status is cleared, then it needs to re-raise the interrupt once the master interrupt status is cleared. (And vice-versa). That's why in this commit, when the master interrupt status is cleared and the interrupt line is lowered, we call the slave interrupt _raise_ function, to see if the interrupt was pending. (And again, vice-versa). Signed-off-by: Peter Delevoryas <pdel@fb.com> Message-Id: <20220630045133.32251-8-me@pjd.dev> Signed-off-by: Cédric Le Goater <clg@kaod.org>
=========== QEMU README =========== QEMU is a generic and open source machine & userspace emulator and virtualizer. QEMU is capable of emulating a complete machine in software without any need for hardware virtualization support. By using dynamic translation, it achieves very good performance. QEMU can also integrate with the Xen and KVM hypervisors to provide emulated hardware while allowing the hypervisor to manage the CPU. With hypervisor support, QEMU can achieve near native performance for CPUs. When QEMU emulates CPUs directly it is capable of running operating systems made for one machine (e.g. an ARMv7 board) on a different machine (e.g. an x86_64 PC board). QEMU is also capable of providing userspace API virtualization for Linux and BSD kernel interfaces. This allows binaries compiled against one architecture ABI (e.g. the Linux PPC64 ABI) to be run on a host using a different architecture ABI (e.g. the Linux x86_64 ABI). This does not involve any hardware emulation, simply CPU and syscall emulation. QEMU aims to fit into a variety of use cases. It can be invoked directly by users wishing to have full control over its behaviour and settings. It also aims to facilitate integration into higher level management layers, by providing a stable command line interface and monitor API. It is commonly invoked indirectly via the libvirt library when using open source applications such as oVirt, OpenStack and virt-manager. QEMU as a whole is released under the GNU General Public License, version 2. For full licensing details, consult the LICENSE file. Documentation ============= Documentation can be found hosted online at `<https://www.qemu.org/documentation/>`_. The documentation for the current development version that is available at `<https://www.qemu.org/docs/master/>`_ is generated from the ``docs/`` folder in the source tree, and is built by `Sphinx <https://www.sphinx-doc.org/en/master/>_`. Building ======== QEMU is multi-platform software intended to be buildable on all modern Linux platforms, OS-X, Win32 (via the Mingw64 toolchain) and a variety of other UNIX targets. The simple steps to build QEMU are: .. code-block:: shell mkdir build cd build ../configure make Additional information can also be found online via the QEMU website: * `<https://wiki.qemu.org/Hosts/Linux>`_ * `<https://wiki.qemu.org/Hosts/Mac>`_ * `<https://wiki.qemu.org/Hosts/W32>`_ Submitting patches ================== The QEMU source code is maintained under the GIT version control system. .. code-block:: shell git clone https://gitlab.com/qemu-project/qemu.git When submitting patches, one common approach is to use 'git format-patch' and/or 'git send-email' to format & send the mail to the qemu-devel@nongnu.org mailing list. All patches submitted must contain a 'Signed-off-by' line from the author. Patches should follow the guidelines set out in the `style section <https://www.qemu.org/docs/master/devel/style.html>` of the Developers Guide. Additional information on submitting patches can be found online via the QEMU website * `<https://wiki.qemu.org/Contribute/SubmitAPatch>`_ * `<https://wiki.qemu.org/Contribute/TrivialPatches>`_ The QEMU website is also maintained under source control. .. code-block:: shell git clone https://gitlab.com/qemu-project/qemu-web.git * `<https://www.qemu.org/2017/02/04/the-new-qemu-website-is-up/>`_ A 'git-publish' utility was created to make above process less cumbersome, and is highly recommended for making regular contributions, or even just for sending consecutive patch series revisions. It also requires a working 'git send-email' setup, and by default doesn't automate everything, so you may want to go through the above steps manually for once. For installation instructions, please go to * `<https://github.com/stefanha/git-publish>`_ The workflow with 'git-publish' is: .. code-block:: shell $ git checkout master -b my-feature $ # work on new commits, add your 'Signed-off-by' lines to each $ git publish Your patch series will be sent and tagged as my-feature-v1 if you need to refer back to it in the future. Sending v2: .. code-block:: shell $ git checkout my-feature # same topic branch $ # making changes to the commits (using 'git rebase', for example) $ git publish Your patch series will be sent with 'v2' tag in the subject and the git tip will be tagged as my-feature-v2. Bug reporting ============= The QEMU project uses GitLab issues to track bugs. Bugs found when running code built from QEMU git or upstream released sources should be reported via: * `<https://gitlab.com/qemu-project/qemu/-/issues>`_ If using QEMU via an operating system vendor pre-built binary package, it is preferable to report bugs to the vendor's own bug tracker first. If the bug is also known to affect latest upstream code, it can also be reported via GitLab. For additional information on bug reporting consult: * `<https://wiki.qemu.org/Contribute/ReportABug>`_ ChangeLog ========= For version history and release notes, please visit `<https://wiki.qemu.org/ChangeLog/>`_ or look at the git history for more detailed information. Contact ======= The QEMU community can be contacted in a number of ways, with the two main methods being email and IRC * `<mailto:qemu-devel@nongnu.org>`_ * `<https://lists.nongnu.org/mailman/listinfo/qemu-devel>`_ * #qemu on irc.oftc.net Information on additional methods of contacting the community can be found online via the QEMU website: * `<https://wiki.qemu.org/Contribute/StartHere>`_