Documentation: x86 device tree processing and memory map
Add documentation on: * FSP Silicon Init * How to start the x86 device tree processing for ramstage * Disabling the PCI devices * Generic PCI device drivers * Memory map support TEST=None Change-Id: If8f729a0ea1d48db4d5ec1d4ae3ad693e9fe44f0 Signed-off-by: Lee Leahy <leroy.p.leahy@intel.com> Reviewed-on: https://review.coreboot.org/13718 Tested-by: build bot (Jenkins) Reviewed-by: Martin Roth <martinroth@google.com>
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Lee Leahy
@@ -26,6 +26,12 @@
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<li>Add the <a href="#MemoryInit">MemoryInit</a> Support</li>
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</ol>
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</li>
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<li><a href="#Ramstage">Ramstage</a>
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<ol type="A">
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<li><a href="#DeviceTree">Start Device Tree Processing</a></li>
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<li>Set up the <a href="#MemoryMap">Memory Map"</a></li>
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</ol>
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</li>
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</ol>
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@@ -382,6 +388,176 @@ Use the following steps to debug the call to TempRamInit:
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<hr>
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<p>Modified: 31 January 2016</p>
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<h1><a name="Ramstage">Ramstage</a></h1>
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<h2><a name="DeviceTree">Start Device Tree Processing</a></h2>
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<p>
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The src/mainboard/<Vendor>/<Board>/devicetree.cb file drives the
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execution during ramstage. This file is processed by the util/sconfig utility
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to generate build/mainboard/<Vendor>/<Board>/static.c. The various
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state routines in
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src/lib/<a target="_blank" href="http://review.coreboot.org/gitweb?p=coreboot.git;a=blob;f=src/lib/hardwaremain.c;hb=HEAD#l128">hardwaremain.c</a>
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call dev_* routines which use the tables in static.c to locate operation tables
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associated with the various chips and devices. After location the operation
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tables, the state routines call one or more functions depending upon the
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state of the state machine.
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</p>
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<h3><a name="ChipOperations">Chip Operations</a></h3>
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<p>
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Kick-starting the ramstage state machine requires creating the operation table
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for the chip listed in devicetree.cb:
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</p>
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<ol>
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<li>Edit src/soc/<SoC Vendor>/<SoC Family>/chip.c:
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<ol type="A">
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<li>
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This chip's operation table has the name
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soc_<SoC Vendor>_<SoC Family>_ops which is derived from the
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chip path specified in the devicetree.cb file.
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</li>
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<li>Use the CHIP_NAME macro to specify the name for the chip</li>
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<li>For FSP 1.1, specify a .init routine which calls intel_silicon_init</li>
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</ol>
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</li>
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<li>Edit src/soc/<SoC Vendor>/<SoC Family>/Makefile.inc and add chip.c to ramstage</li>
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</ol>
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<h3>Domain Operations</h3>
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<p>
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coreboot uses the domain operation table to initiate operations on all of the
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devices in the domain. By default coreboot enables all PCI devices which it
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finds. Listing a device in devicetree.cb gives the board vendor control over
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the device state. Non-PCI devices may also be listed under PCI device such as
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the LPC bus or SMbus devices.
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</p>
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<ol>
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<li>Edit src/soc/<SoC Vendor>/<SoC Family>/chip.c:
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<ol type="A">
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<li>
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The domain operation table is typically placed in
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src/soc/<SoC Vendor>/<SoC Family>/chip.c.
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The table typically looks like the following:
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<pre><code>static struct device_operations pci_domain_ops = {
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.read_resources = pci_domain_read_resources,
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.set_resources = pci_domain_set_resources,
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.scan_bus = pci_domain_scan_bus,
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.ops_pci_bus = pci_bus_default_ops,
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};
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</code></pre>
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</li>
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<li>
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Create a .enable_dev entry in the chip operations table which points to a
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routine which sets the domain table for the device with the DEVICE_PATH_DOMAIN.
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<pre><code> if (dev->path.type == DEVICE_PATH_DOMAIN) {
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dev->ops = &pci_domain_ops;
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}
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</code></pre>
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</li>
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<li>
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During the BS_DEV_ENUMERATE state, ramstage now display the device IDs
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for the PCI devices on the bus.
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</li>
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</ol>
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</li>
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<li>Set CONFIG_DEBUG_BOOT_STATE=y in the .config file</li>
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<li>
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Debug the result until the PCI vendor and device IDs are displayed
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during the BS_DEV_ENUMERATE state.
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</li>
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</ol>
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<h2><a name="DeviceDrivers">PCI Device Drivers</a></h2>
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<p>
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PCI device drivers consist of a ".c" file which contains a "pci_driver" data
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structure at the end of the file with the attribute tag "__pci_driver". This
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attribute tag places an entry into a link time table listing the various
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coreboot device drivers.
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</p>
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<p>
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Specify the following fields in the table:
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</p>
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<ol>
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<li>.vendor - PCI vendor ID value of the device</li>
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<li>.device - PCI device ID value of the device or<br>
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.devices - Address of a zero terminated array of PCI device IDs
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</li>
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<li>.ops - Operations table for the device. This is the address
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of a "static struct device_operations" data structure specifying
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the routines to execute during the different states and sub-states
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of ramstage's processing.
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</li>
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<li>Turn on the device in mainboard/<Vendor>/<Board>/devicetree.cb</li>
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<li>
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Debug until the device is on and properly configured in coreboot and
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usable by the payload
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</li>
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</ol>
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<h3><a name="SubsystemIds">Subsystem IDs</a></h3>
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<p>
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PCI subsystem IDs are assigned during the BS_DEV_ENABLE state. The device
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driver may use the common mechanism to assign subsystem IDs by adding
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the ".ops_pci" to the pci_driver data structure. This field points to
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a "struct pci_operations" that specifies a routine to set the subsystem
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IDs for the device. The routine might look something like this:
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</p>
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<pre><code>static void pci_set_subsystem(device_t dev, unsigned vendor, unsigned device)
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{
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if (!vendor || !device) {
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vendor = pci_read_config32(dev, PCI_VENDOR_ID);
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device = vendor >> 16;
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}
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printk(BIOS_SPEW,
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"PCI: %02x:%02x:%d subsystem vendor: 0x%04x, device: 0x%04x\n",
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0, PCI_SLOT(dev->path.pci.devfn), PCI_FUNC(dev->path.pci.devfn),
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vendor & 0xffff, device);
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pci_write_config32(dev, PCI_SUBSYSTEM_VENDOR_ID,
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((device & 0xffff) << 16) | (vendor & 0xffff));
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}
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</code></pre>
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<h2>Set up the <a name="MemoryMap">Memory Map</a></h2>
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<p>
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The memory map is built by the various PCI device drivers during the
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BS_DEV_RESOURCES state of ramstage. The northcluster driver will typically
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specify the DRAM resources while the other drivers will typically specify
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the IO resources. These resources are hung off the device_t data structure by
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src/device/device_util.c/<a target="_blank" href="http://review.coreboot.org/gitweb?p=coreboot.git;a=blob;f=src/device/device_util.c;hb=HEAD#l448">new_resource</a>.
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</p>
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<p>
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During the BS_WRITE_TABLES state, coreboot collects these resources and
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places them into a data structure identified by LB_MEM_TABLE.
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</p>
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<p>
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Edit the device driver file:
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</p>
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<ol>
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<li>
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Implement a read_resources routine which calls macros defined in
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src/include/device/<a target="_blank" href="http://review.coreboot.org/gitweb?p=coreboot.git;a=blob;f=src/include/device/device.h;hb=HEAD#l237">device.h</a>
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like:
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<ul>
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<li>ram_resource</li>
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<li>reserved_ram_resource</li>
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<li>bad_ram_resource</li>
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<li>uma_resource</li>
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<li>mmio_resource</li>
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</ul>
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</li>
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</ol>
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<p>
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Testing: Verify that the resources are properly displayed by coreboot during the BS_WRITE_TABLES state.
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</p>
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<hr>
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<p>Modified: 18 February 2016</p>
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</body>
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</html>
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