Linus Walleij linus.walleij@linaro.org writes:
We were previously selecting 1024x768 and 32BPP as the default set-up for the PL111 consumers.
This does not work on elder systems: the device tree bindings support a property "max-memory-bandwidth" in bytes/second that states that if you exceed this the memory bus will saturate. The result is flickering and unstable images.
Parse the "max-memory-bandwidth" and respect it when intializing the driver. On the RealView PB11MP, Versatile and Integrator/CP we get a nice console as default with this code.
Signed-off-by: Linus Walleij linus.walleij@linaro.org
ChangeLog v2->v3:
- Account for the case where there is no bandwidth limitation so priv->memory_bw is zero. Then just accept any modes.
ChangeLog v1->v2:
- Exploit the new .mode_valid() callback we added to the simple KMS helper.
- Use the hardcoded bits per pixel per variant instead of trying to be heuristic about this setting for now.
drivers/gpu/drm/pl111/pl111_display.c | 36 +++++++++++++++++++++++++++++++++++ drivers/gpu/drm/pl111/pl111_drm.h | 1 + drivers/gpu/drm/pl111/pl111_drv.c | 6 ++++++ 3 files changed, 43 insertions(+)
diff --git a/drivers/gpu/drm/pl111/pl111_display.c b/drivers/gpu/drm/pl111/pl111_display.c index d75923896609..577e61950e16 100644 --- a/drivers/gpu/drm/pl111/pl111_display.c +++ b/drivers/gpu/drm/pl111/pl111_display.c @@ -50,6 +50,41 @@ irqreturn_t pl111_irq(int irq, void *data) return status; }
+static enum drm_mode_status +pl111_mode_valid(struct drm_crtc *crtc,
const struct drm_display_mode *mode)+{
- struct drm_device *drm = crtc->dev;
- struct pl111_drm_dev_private *priv = drm->dev_private;
- u32 cpp = priv->variant->fb_bpp / 8;
- u64 bw;
- /*
* We use the pixelclock to also account for interlaced modes, the* resulting bandwidth is in bytes per second.*/- bw = mode->clock * 1000; /* In Hz */
- bw = bw * mode->hdisplay * mode->vdisplay * cpp;
- bw = div_u64(bw, mode->htotal * mode->vtotal);
- /*
* If no bandwidth constraints, anything goes, else* check if we are too fast.*/- if (priv->memory_bw && (bw > priv->memory_bw)) {
DRM_INFO("%d x %d @ %d Hz, %d cpp, bw %llu too fast\n",mode->hdisplay, mode->vdisplay,mode->clock * 1000, cpp, bw);return MODE_BAD;- }
- DRM_INFO("%d x %d @ %d Hz, %d cpp, bw %llu bytes/s OK\n",
mode->hdisplay, mode->vdisplay,mode->clock * 1000, cpp, bw);
I think the DRM_INFO should be DRM_DEBUG_KMS. With that,
Reviewed-by: Eric Anholt eric@anholt.net