Patrick Georgi submitted this change.
Documentation/superio: add formatting to generic PNP documentation
Change-Id: Id12ec4d5f11f4285a1379cf32a5d0f6cd2ce9e70
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38519
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
---
M Documentation/superio/common/pnp.md
1 file changed, 23 insertions(+), 23 deletions(-)
diff --git a/Documentation/superio/common/pnp.md b/Documentation/superio/common/pnp.md
index 314cac2..3c17259 100644
--- a/Documentation/superio/common/pnp.md
+++ b/Documentation/superio/common/pnp.md
@@ -15,13 +15,13 @@
Super I/O chips connected via LPC to the southbridge usually have their
I/O-mapped configuration interface with a size of two bytes at the base
-address 0x2e or 0x4e. Other PNP devices have their configuration
+address `0x2e` or `0x4e`. Other PNP devices have their configuration
interface at other addresses.
The two byte registers allow access to an indirect 256 bytes big
-register space that contains the configuration. By writing the index
-to the lower byte (e.g. 0x2e), you can access the register contents at
-that index by reading/writing the higher byte (e.g. 0x2f).
+register space that contains the configuration. By writing the index to
+the lower byte (e.g. `0x2e`), you can access the register contents at
+that index by reading/writing the higher byte (e.g. `0x2f`).
To prevent accidental changes of the Super I/O (SIO) configuration,
the SIOs need a configuration mode unlock sequence. After changing the
@@ -31,18 +31,18 @@
## Logical device numbers (LDN)
Each PNP device can contain multiple logical devices. The bytes from
-0x00 to 0x2f in the indirect configuration register space are common
-for all LDNs, but some SIO chips require a certain LDN to be selected
-in order to write certain registers in there. An LDN gets selected by
-writing the LDN number to the LDN select register 0x07. Registers 0x30
-to 0xFF are specific to each LDN number.
+`0x00` to `0x2f` in the indirect configuration register space are common
+for all LDNs, but some SIO chips require a certain LDN to be selected in
+order to write certain registers in there. An LDN gets selected by
+writing the LDN number to the LDN select register `0x07`. Registers
+`0x30` to `0xff` are specific to each LDN number.
coreboot encodes the physical LDN number in the lower byte of the LDN
number.
### Virtual logical device numbers
-Register 0x30 is the LDN enable register and since it is an 8 bit
+Register `0x30` is the LDN enable register and since it is an 8 bit
register, it can contain up to 8 enable bits for different parts of
the functionality of that logical device. To set a certain enable bit
in one physical LDN, the concept of virtual LDNs was introduced.
@@ -54,7 +54,7 @@
## I/O resources
-Starting at register address 0x60, each LDN has 2 byte wide I/O base
+Starting at register address `0x60`, each LDN has 2 byte wide I/O base
address registers. The size of an I/O resource is always a power of
two.
@@ -67,29 +67,29 @@
the resource has N address bits and a size of 2\*\*N bytes. The mask
address is also the highest possible address to map the I/O region.
-A typical example for an I/O resource mask is 0x07f8 which is
-0b0000011111111000 in binary notation. The three LSBs are zeros here,
+A typical example for an I/O resource mask is `0x07f8` which is
+`0b0000011111111000` in binary notation. The three LSBs are zeros here,
so it's an eight byte I/O resource with three address offset bits
inside the resource. The highest base address it can be mapped to is
-0x07f8, so the region will end at 0x07ff.
+`0x07f8`, so the region will end at `0x07ff`.
The Super I/O datasheets typically contain the information about the
I/O resource masks. On most Super I/O chips the mask can also be found
-out by writing 0xffff to the corresponding I/O base address register
+out by writing `0xffff` to the corresponding I/O base address register
and reading back the value; since the lowest and highest bits are
hard-wired to zero according to the I/O resource size and maximal
possible I/O address, this gives the mask.
## IRQ resources
-Each physical LDN has up to two configurable interrupt request
-register pairs 0x70, 0x71 and 0x72, 0x73. Each pair can be configured
-to use a certain IRQ number. Writing 1 to 15 into the first register
+Each physical LDN has up to two configurable interrupt request register
+pairs `0x70`, `0x71` and `0x72`, `0x73`. Each pair can be configured to
+use a certain IRQ number. Writing 1 to 15 into the first register
selects the IRQ number generated by the corresponding IRQ source and
-enables IRQ generation; writing 0 to it disables the generation of
-IRQs for the source. The second register selects the IRQ type (level
-or edge) and IRQ level (high or low). For LPC SIOs the IRQ type is
-hard-wired to edge.
+enables IRQ generation; writing 0 to it disables the generation of IRQs
+for the source. The second register selects the IRQ type (level or edge)
+and IRQ level (high or low). For LPC SIOs the IRQ type is hard-wired to
+edge.
On the LPC bus a shared SERIRQ line is used to signal IRQs to the
host; the IRQ number gets encoded by the number of LPC clock cycles
@@ -106,7 +106,7 @@
## DRQ resources
Each physical LDN has two legacy ISA-style DMA request channel
-registers at 0x74 and 0x75. Those are only used for legacy devices
+registers at `0x74` and `0x75`. Those are only used for legacy devices
like parallel printer ports or floppy disk controllers.
Each device using LPC legacy DMA needs its own LDMA line to the host.
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