readme: Add Intel information

Add some information about the new available Intel driver and adjust
formatting of the code examples.
Signed-off-by: Antonio Caggiano <antonio.caggiano@collabora.com>
Reviewed-by: Rohan Garg <rohan.garg@collabora.com>
Reviewed-by: Gert Wollny <gert.wollny@collabora.com>

README.md

 Graphics Perfetto producers
 ---------------------------
 
-This project contains a collection of graphics-related [Perfetto producers](https://perfetto.dev/#/architecture.md). A producer is a client process for the Perfetto tracing service. Currently under development are the following producers:
+This project contains a collection of graphics-related [Perfetto producers](https://perfetto.dev/#/architecture.md). A producer is a client process for the Perfetto tracing service. Currently available are the following producers:
 
 - Panfrost performance counters
 - Weston timeline debug stream
+- Intel performance counters
 
 ## Build
 
@@ -12,21 +13,21 @@ This section guides you through the building process assuming you are compiling
 
 1. Install dependencies:
 
-```sh
-apt install build-essential meson cmake libwayland-dev rapidjson-dev libdrm-dev libprotobuf-dev libgtest-dev libdocopt-dev
-```
+   ```sh
+   apt install build-essential meson cmake libwayland-dev rapidjson-dev libdrm-dev libprotobuf-dev libgtest-dev libdocopt-dev
+   ```
 
 2. Generate the project:
 
-```sh
-meson build
-```
+   ```sh
+   meson build
+   ```
 
 3. Compile and run tests (it may take a while):
 
-```sh
-ninja -C build test
-```
+   ```sh
+   ninja -C build test
+   ```
 
 ### Cross-compile
 
@@ -40,32 +41,32 @@ To cross-compile on amd64 using clang, follow these steps:
 
 1. Change directory to `perfetto`
 
-```sh
-cd <path>/perfetto
-```
+   ```sh
+   cd <path>/perfetto
+   ```
 
 2. Generate a build directory
 
-```sh
-tools/gn args out/arm64
-```
+   ```sh
+   tools/gn args out/arm64
+   ```
 
-Typing in the following GN args
+   Typing in the following GN args
 
-```js
-// args.gn
-target_os = "linux"
-target_cpu = "arm64"
-is_debug = false
-target_sysroot = "/usr/aarch64-linux-gnu"
-target_gcc_toolchain = "/usr"
-```
+   ```js
+   // args.gn
+   target_os = "linux"
+   target_cpu = "arm64"
+   is_debug = false
+   target_sysroot = "/usr/aarch64-linux-gnu"
+   target_gcc_toolchain = "/usr"
+   ```
 
 3. Compile perfetto and the tracing service
 
-```sh
-tools/ninja -C out/arm64 perfetto traced traced_probes
-```
+   ```sh
+   tools/ninja -C out/arm64 perfetto traced traced_probes
+   ```
 
 #### Cross-compile gfx-pps producers
 
@@ -73,45 +74,45 @@ To cross-compile with meson, you need to take these steps:
 
 1. Prepare a chroot for cross-building
 
-```sh
-sudo debootstrap --variant=buildd focal /srv/target/focal
-sudo chroot /srv/target/focal
-mount -t proc proc /proc
-```
+   ```sh
+   sudo debootstrap --variant=buildd focal /srv/target/focal
+   sudo chroot /srv/target/focal
+   mount -t proc proc /proc
+   ```
 
 2. Add arm64 to `/etc/apt/souces.list`
 
-```
-deb [arch=amd64] http://archive.ubuntu.com/ubuntu focal main
-deb [arch=arm64] http://ports.ubuntu.com/ubuntu-ports focal main
-```
+   ```
+   deb [arch=amd64] http://archive.ubuntu.com/ubuntu focal main
+   deb [arch=arm64] http://ports.ubuntu.com/ubuntu-ports focal main
+   ```
 
 3. Enable multiarch by adding arm64
 
-```sh
-dpkg --add-architecture arm64
-```
+   ```sh
+   dpkg --add-architecture arm64
+   ```
 
 4. Install the arm64 toolchain and other required packages:
 
-```sh
-apt update
-apt install build-essential libc6-arm64-cross gcc-aarch64-linux-gnu g++-aarch64-linux-gnu meson cmake libdrm-dev:arm64 libwayland-dev:arm64 libprotobuf-dev:arm64 rapidjson-dev:arm64 libgtest-dev:arm64 libdocopt-dev:arm64
-```
+   ```sh
+   apt update
+   apt install build-essential libc6-arm64-cross gcc-aarch64-linux-gnu g++-aarch64-linux-gnu meson cmake libdrm-dev:arm64 libwayland-dev:arm64 libprotobuf-dev:arm64 rapidjson-dev:arm64 libgtest-dev:arm64 libdocopt-dev:arm64
+   ```
 
 5. Create a [cross file](https://mesonbuild.com/Cross-compilation.html) for meson like the following snippet: [aarch64-linux](https://gitlab.freedesktop.org/Fahien/gfx-pps/snippet/1086)
 
 6. Generate the project using that cross file:
 
-```sh
-meson build/arm64 --cross-file aarch64-linux
-```
+   ```sh
+   meson build/arm64 --cross-file aarch64-linux
+   ```
 
 7. Compile and run tests
 
-```sh
-ninja -C build/arm64 test
-```
+   ```sh
+   ninja -C build/arm64 test
+   ```
 
 ## Run
 
@@ -123,10 +124,10 @@ To capture a trace with perfetto you need to take the following steps:
 
 3. Change directory to `perfetto` and run a [convenience script](https://perfetto.dev/#/running.md) to start the tracing service:
 
-```sh
-cd <path>/perfetto
-CONFIG=test.cfg OUT=out/build ./tools/tmux
-```
+   ```sh
+   cd <path>/perfetto
+   CONFIG=test.cfg OUT=out/build ./tools/tmux
+   ```
 
 4. Start other producers you may need, like `producer-gpu` or `producer-weston`.
 
@@ -138,18 +139,32 @@ CONFIG=test.cfg OUT=out/build ./tools/tmux
 
 ### GPU producer
 
-The GPU producer contains at the current state a data-source able to query GPU performance counters using the Panfrost driver. The data-source uses unstable ioctls that behave correctly on kernel version [5.4.23+](https://lwn.net/Articles/813601/) and [5.5.7+](https://lwn.net/Articles/813600/). To run the producer, follow these two simple steps:
+The GPU producer contains at the current state a data-source able to query performance counters using a Panfrost driver for Arm Mali devices, or an Intel driver for Intel Graphics devices.
+
+#### Panfrost driver
+
+The Panfrost driver uses unstable ioctls that behave correctly on kernel version [5.4.23+](https://lwn.net/Articles/813601/) and [5.5.7+](https://lwn.net/Articles/813600/).
+
+To run the producer, follow these two simple steps:
 
 1. Enable Panfrost unstable ioctls via kernel parameter:
 
-```sh
-modprobe panfrost unstable_ioctls=1
-```
+   ```sh
+   modprobe panfrost unstable_ioctls=1
+   ```
 
 2. Run the producer:
 
+   ```sh
+   ./build/producer-gpu
+   ```
+
+#### Intel driver
+
+The Intel driver needs root access to read system-wide [RenderBasic]() performance counters, so you can simply run it with sudo:
+
 ```sh
-./build/producer-gpu
+sudo ./build/producer-gpu
 ```
 
 ### Weston producer
@@ -158,15 +173,15 @@ The weston producer needs the debug protocol to be present in weston. If the deb
 
 1. Before running `producer-weston`, make sure weston is started with the `--debug` argument:
 
-```sh
-weston --debug
-```
+   ```sh
+   weston --debug
+   ```
 
 2. Execute the producer:
 
-```sh
-./build/producer-weston
-```
+   ```sh
+   ./build/producer-weston
+   ```
 
 ## Troubleshooting