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[Qemu-devel] [PATCH v4 2/7] fw_cfg DMA interface documentation
From: |
Marc Marí |
Subject: |
[Qemu-devel] [PATCH v4 2/7] fw_cfg DMA interface documentation |
Date: |
Thu, 1 Oct 2015 14:16:54 +0200 |
Add fw_cfg DMA interface specification in the documentation.
Based on Gerd Hoffman's initial implementation.
Signed-off-by: Marc Marí <address@hidden>
Reviewed-by: Peter Maydell <address@hidden>
---
docs/specs/fw_cfg.txt | 65 +++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 61 insertions(+), 4 deletions(-)
diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt
index 5bc7b96..2d6b2da 100644
--- a/docs/specs/fw_cfg.txt
+++ b/docs/specs/fw_cfg.txt
@@ -76,6 +76,13 @@ increasing address order, similar to memcpy().
Selector Register IOport: 0x510
Data Register IOport: 0x511
+DMA Address IOport: 0x514
+
+=== ARM Register Locations ===
+
+Selector Register address: Base + 8 (2 bytes)
+Data Register address: Base + 0 (8 bytes)
+DMA Address address: Base + 16 (8 bytes)
== Firmware Configuration Items ==
@@ -86,11 +93,12 @@ by selecting the "signature" item using key 0x0000
(FW_CFG_SIGNATURE),
and reading four bytes from the data register. If the fw_cfg device is
present, the four bytes read will contain the characters "QEMU".
-=== Revision (Key 0x0001, FW_CFG_ID) ===
+=== Revision / feature bitmap (Key 0x0001, FW_CFG_ID) ===
-A 32-bit little-endian unsigned int, this item is used as an interface
-revision number, and is currently set to 1 by QEMU when fw_cfg is
-initialized.
+A 32-bit little-endian unsigned int, this item is used to check for enabled
+features.
+ - Bit 0: traditional interface. Always set.
+ - Bit 1: DMA interface.
=== File Directory (Key 0x0019, FW_CFG_FILE_DIR) ===
@@ -132,6 +140,55 @@ Selector Reg. Range Usage
In practice, the number of allowed firmware configuration items is given
by the value of FW_CFG_MAX_ENTRY (see fw_cfg.h).
+= Guest-side DMA Interface =
+
+If bit 1 of the feature bitmap is set, the DMA interface is present. This does
+not replace the existing fw_cfg interface, it is an add-on. This interface
+can be used through the 64-bit wide address register.
+
+The address register is in big-endian format. The value for the register is 0
+at startup and after an operation. A write to the lower half triggers an
+operation. This means that operations with 32-bit addresses can be triggered
+with just one write, whereas operations with 64-bit addresses can be
+triggered with one 64-bit write or two 32-bit writes, starting with the
+higher part.
+
+In this register, the physical address of a FWCfgDmaAccess structure in RAM
+should be written. This is the format of the FWCfgDmaAccess structure:
+
+typedef struct FWCfgDmaAccess {
+ uint32_t control;
+ uint32_t length;
+ uint64_t address;
+} FWCfgDmaAccess;
+
+The fields of the structure are in big endian mode, and the field at the lowest
+address is the "control" field.
+
+The "control" field has the following bits:
+ - Bit 0: Error
+ - Bit 1: Read
+ - Bit 2: Skip
+ - Bit 3: Select. The upper 16 bits are the selected index.
+
+When an operation is triggered, if the "control" field has bit 3 set, the
+upper 16 bits are interpreted as an index of a firmware configuration item.
+This has the same effect as writing the selector register.
+
+If the "control" field has bit 1 set, a read operation will be performed.
+"length" bytes for the current selector and offset will be copied into the
+physical RAM address specified by the "address" field.
+
+If the "control" field has bit 2 set (and not bit 1), a skip operation will be
+performed. The offset for the current selector will be advanced "length" bytes.
+
+To check the result, read the "control" field:
+ error bit set -> something went wrong.
+ all bits cleared -> transfer finished successfully.
+ otherwise -> transfer still in progress (doesn't happen
+ today due to implementation not being async,
+ but may in the future).
+
= Host-side API =
The following functions are available to the QEMU programmer for adding
--
2.4.3
- [Qemu-devel] [PATCH v4 3/7] Implement fw_cfg DMA interface, (continued)
- Re: [Qemu-devel] [PATCH v4 3/7] Implement fw_cfg DMA interface, Stefan Hajnoczi, 2015/10/08
- Re: [Qemu-devel] [PATCH v4 3/7] Implement fw_cfg DMA interface, Peter Maydell, 2015/10/08
- Re: [Qemu-devel] [PATCH v4 3/7] Implement fw_cfg DMA interface, Stefan Hajnoczi, 2015/10/09
- Re: [Qemu-devel] [PATCH v4 3/7] Implement fw_cfg DMA interface, Marc Marí, 2015/10/09
- Re: [Qemu-devel] [PATCH v4 3/7] Implement fw_cfg DMA interface, Marc Marí, 2015/10/08
[Qemu-devel] [PATCH v4 2/7] fw_cfg DMA interface documentation,
Marc Marí <=
[Qemu-devel] [PATCH v4 1/7] fw_cfg: document fw_cfg_modify_iXX() update functions, Marc Marí, 2015/10/08
[Qemu-devel] [PATCH v4 6/7] Make the kernel image in the fw_cfg DMA interface bootable, Marc Marí, 2015/10/08
- Re: [Qemu-devel] [PATCH v4 6/7] Make the kernel image in the fw_cfg DMA interface bootable, Laszlo Ersek, 2015/10/08
- Re: [Qemu-devel] [PATCH v4 6/7] Make the kernel image in the fw_cfg DMA interface bootable, Gerd Hoffmann, 2015/10/08
- Re: [Qemu-devel] [PATCH v4 6/7] Make the kernel image in the fw_cfg DMA interface bootable, Kevin O'Connor, 2015/10/08
- Re: [Qemu-devel] [PATCH v4 6/7] Make the kernel image in the fw_cfg DMA interface bootable, Laszlo Ersek, 2015/10/08
- Re: [Qemu-devel] [PATCH v4 6/7] Make the kernel image in the fw_cfg DMA interface bootable, Gerd Hoffmann, 2015/10/08
- Re: [Qemu-devel] [PATCH v4 6/7] Make the kernel image in the fw_cfg DMA interface bootable, Daniel P. Berrange, 2015/10/08
Re: [Qemu-devel] [PATCH v4 6/7] Make the kernel image in the fw_cfg DMA interface bootable, Kevin O'Connor, 2015/10/08