update BARs and Telemetry (#248)

Signed-off-by: Min Ma <min.ma@amd.com>

src/driver/doc/amdnpu.rst

@@ -76,12 +76,28 @@ instance of ERT. Each user channel is bound to its own dedicated mailbox.
 PCIe EP
 -------
 
-NPU is visible to the x86 as a PCIe device with 3 BARS and an MSI-X interrupt
-vector. NPU uses a dedicated high bandwidth SoC level fabric for reading
+NPU is visible to the x86 as a PCIe device with multiple BARs and some MSI-X interrupt
+vectors. NPU uses a dedicated high bandwidth SoC level fabric for reading
 writing into host memory. Each instance of ERT gets its own dedicated MSI-X
 interrupt. MERT gets a single instance of MSI-X interrupt.
 
-TODO, briefly describe the BARs
+The number of PCIe BARs varies depending on the specific device.
+Based on their functions, PCIe BARs can generally be categorized into the
+following types.
+
+* PSP BAR: Expose the AMD PSP (Platform Security Processor) function
+* SMU BAR: Expose the AMD SMU (System Management Unit) function
+* SRAM BAR: Expose ring buffers for the mailbox
+* Mailbox BAR: Expose the mailbox control registers (head, tail and ISR registers etc.)
+* Public Register BAR: Expose public registers
+
+On specific devices, the above-mentioned BAR type might be combined into a single physical PCIe BAR.
+Or a module might require two physical PCIe BARs to be fully functional.
+For example,
+
+* On AMD Phoenix device, PSP, SMU, Public Register BARs are on PCIe BAR index 0.
+* On AMD Strix Point device, Mailbox and Public Register BARs are on PCIe BAR index 0.
+  The PSP has some registers in PCIe BAR index 0 (Public Register BAR) and PCIe BAR index 4 (PSP BAR).
 
 Process Isolation Hardware
 --------------------------
@@ -244,8 +260,11 @@ driver then decodes the error by reading the contents of the buffer pointer.
 Telemetry
 =========
 
-MERT can report various kinds of telemetry information like
-TODO, list the key ones
+MERT can report various kinds of telemetry information like the following:
+* L1 interrupt counter
+* DMA counter
+* Deep Sleep counter
+* etc.
 
 
 References