[Mesa-dev] [PATCH] loader: use drmDeviceUseRevisionFile to prevent waking up the GPUs

[Emil Velikov]

From: Emil Velikov <emil.velikov at collabora.com>

Currently the drmGetDevice[s] API parses the config sysfs file to
retrieve the revision field.

That is required since there's no separate file (nor a libudev call
afaict) that can be used. At the same time doing so causes the device to
be awaken, so if an application creates/destroys a GL context multiple
times they can observe noticeable delays. 2-3s in the case of
firefox/thunderbird/chromium + radeon module.

There's a kernel patch on the PCI mailing list, but until then we can
use drmDeviceUseRevisionFile() which will use separate sysfs files and
default to 0 if the revision one is missing.

Since we don't care about the revision id, we can use that.

Cc: "13.0" <mesa-stable at lists.freedesktop.org>
Cc: Mauro Santos <registo.mailling at gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98502
Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
---
The libdrm version is tentative. An alternative solution is to use
revision file [and default to 0] behind the scenes.

Both options are rather nasty, so any preferences and suggestions are
greatly appreciated.

Mauro, feel free to drop the version hunk (or bump the libdrm version
while building).
---
 configure.ac        | 2 +-
 src/loader/loader.c | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index d215b63..f529f2cf 100644
--- a/configure.ac
+++ b/configure.ac
@@ -68,7 +68,7 @@ OPENCL_VERSION=1
 AC_SUBST([OPENCL_VERSION])
 
 dnl Versions for external dependencies
-LIBDRM_REQUIRED=2.4.66
+LIBDRM_REQUIRED=2.4.72
 LIBDRM_RADEON_REQUIRED=2.4.56
 LIBDRM_AMDGPU_REQUIRED=2.4.63
 LIBDRM_INTEL_REQUIRED=2.4.61
diff --git a/src/loader/loader.c b/src/loader/loader.c
index fe90307..e2e4156 100644
--- a/src/loader/loader.c
+++ b/src/loader/loader.c
@@ -275,6 +275,7 @@ drm_get_pci_id_for_fd(int fd, int *vendor_id, int *chip_id)
    drmDevicePtr device;
    int ret;
 
+   drmDeviceUseRevisionFile();
    if (drmGetDevice(fd, &device) == 0) {
       if (device->bustype == DRM_BUS_PCI) {
          *vendor_id = device->deviceinfo.pci->vendor_id;
-- 
2.10.2