From: Jocelyn Falempe Date: Fri, 17 May 2024 15:09:58 +0000 (+0200) Subject: drm/mgag200: Add an option to disable Write-Combine X-Git-Tag: v6.11-rc1~141^2~24^2~91 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b593ea9406237739d2da42e6f245c390d8a69f43;p=thirdparty%2Flinux.git drm/mgag200: Add an option to disable Write-Combine 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 Reviewed-by: Thomas Zimmermann Link: https://patchwork.freedesktop.org/patch/msgid/20240517151050.624797-3-jfalempe@redhat.com --- 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; }