On 17/05/2024 17:16, Thomas Zimmermann wrote:
Hi
Am 17.05.24 um 17:09 schrieb Jocelyn Falempe:
Unfortunately, the G200 ioburst workaround doesn't work on some
servers like Dell poweredge XR11, XR5610, or HPE XL260. In this case
completely disabling WC is the only option to achieve low-latency.
So this adds a new Kconfig option to disable WC mapping of the G200.
Signed-off-by: Jocelyn Falempe <jfalempe@xxxxxxxxxx>
Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Thanks a lot for the fix.
Thanks for the review, I just merged it to drm-misc-next.
Best regards
Thomas
---
drivers/gpu/drm/mgag200/Kconfig | 10 ++++++++++
drivers/gpu/drm/mgag200/mgag200_drv.c | 6 ++++++
2 files changed, 16 insertions(+)
diff --git a/drivers/gpu/drm/mgag200/Kconfig
b/drivers/gpu/drm/mgag200/Kconfig
index b28c5e4828f47..3096944a8f0ab 100644
--- a/drivers/gpu/drm/mgag200/Kconfig
+++ b/drivers/gpu/drm/mgag200/Kconfig
@@ -11,3 +11,13 @@ config DRM_MGAG200
MGA G200 desktop chips and the server variants. It requires 0.3.0
of the modesetting userspace driver, and a version of mga driver
that will fail on KMS enabled devices.
+
+config DRM_MGAG200_DISABLE_WRITECOMBINE
+ bool "Disable Write Combine mapping of VRAM"
+ depends on DRM_MGAG200 && PREEMPT_RT
+ help
+ The VRAM of the G200 is mapped with Write-Combine to improve
+ performances. This can interfere with real-time tasks; even if
they
+ are running on other CPU cores than the graphics output.
+ Enable this option only if you run realtime tasks on a server
with a
+ Matrox G200.
\ No newline at end of file
diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.c
b/drivers/gpu/drm/mgag200/mgag200_drv.c
index 3883f25ca4d8b..62080cf0f2da4 100644
--- a/drivers/gpu/drm/mgag200/mgag200_drv.c
+++ b/drivers/gpu/drm/mgag200/mgag200_drv.c
@@ -146,12 +146,18 @@ int mgag200_device_preinit(struct mga_device *mdev)
}
mdev->vram_res = res;
+#if defined(CONFIG_DRM_MGAG200_DISABLE_WRITECOMBINE)
+ mdev->vram = devm_ioremap(dev->dev, res->start, resource_size(res));
+ if (!mdev->vram)
+ return -ENOMEM;
+#else
mdev->vram = devm_ioremap_wc(dev->dev, res->start,
resource_size(res));
if (!mdev->vram)
return -ENOMEM;
/* Don't fail on errors, but performance might be reduced. */
devm_arch_phys_wc_add(dev->dev, res->start, resource_size(res));
+#endif
return 0;
}
