On Mon, 2010-04-12 at 17:09 +0800, Zhenyu Wang wrote: > Update the self-refresh watermark for display plane/cursor and enable > the memory self-refresh on Ironlake. The watermark is also updated for > the active display plane. > > More than 1W idle power is saved on one Ironlake laptop after enabling > memory self-refresh.
Looks good at a quick read, though I haven't tested it yet.
> + /* Calculate and update the watermark for plane A */
> + if (planea_clock) {
> + entries_required = ((planea_clock / 1000) * pixel_size *
> + ILK_LP0_PLANE_LATENCY) / 1000;
> + entries_required = DIV_ROUND_UP(entries_required,
> + ironlake_display_wm_info.cacheline_size);
> + planea_wm = entries_required +
> + ironlake_display_wm_info.guard_size;
> +
> + if (planea_wm > (int)ironlake_display_wm_info.max_wm)
> + planea_wm = ironlake_display_wm_info.max_wm;
> +
> + cursora_wm = 16;
> + reg_value = I915_READ(WM0_PIPEA_ILK);
> + reg_value &= ~(WM0_PIPE_PLANE_MASK | WM0_PIPE_CURSOR_MASK);
> + reg_value |= (planea_wm << WM0_PIPE_PLANE_SHIFT) |
> + (cursora_wm & WM0_PIPE_CURSOR_MASK);
> + I915_WRITE(WM0_PIPEA_ILK, reg_value);
> + DRM_DEBUG_KMS("FIFO watermarks For pipe A - plane %d, "
> + "cursor: %d\n", planea_wm, cursora_wm);
> + }
This doesn't adjust the video sprite plane watermark. I suppose it
doesn't really matter, since we're not enabling it yet, but for clarity
I'd also mask off WM0_PIPE_SPRITE_MASK.
Also, the cursor watermark is a magic number. I assume it's derived
from the hardware cursor size. In which case, it'd be nice to show the
derivation; Ironlake can do hardware cursors up to 256x256, it'd be nice
to have that work automatically when and if we enable that in the
driver.
> + /* configure watermark and enable self-refresh */
> + reg_value = I915_READ(WM1_LP_ILK);
> + reg_value &= ~(WM1_LP_LATENCY_MASK | WM1_LP_SR_MASK |
> + WM1_LP_CURSOR_MASK);
> + reg_value |= WM1_LP_SR_EN |
> + (ilk_sr_latency << WM1_LP_LATENCY_SHIFT) |
> + (sr_wm << WM1_LP_SR_SHIFT) | cursor_wm;
> +
> + I915_WRITE(WM1_LP_ILK, reg_value);
> + DRM_DEBUG_KMS("self-refresh watermark: display plane %d "
> + "cursor %d\n", sr_wm, cursor_wm);
What are the conditions for entering LP2 or LP3 state, and is it worth
trying to set them up too?
> + /*
> + * According to the spec the following bits should be set in
> + * order to enable memory self-refresh
> + * The bit 22/21 of 0x42004
> + * The bit 5 of 0x42020
> + * The bit 15 of 0x45000
> + */
> + if (IS_IRONLAKE(dev)) {
> + I915_WRITE(ILK_DISPLAY_CHICKEN2,
> + (I915_READ(ILK_DISPLAY_CHICKEN2) |
> + ILK_DPARB_GATE | ILK_VSDPFD_FULL));
I can only hope this is named "chicken" in allusion to:
http://en.wikipedia.org/wiki/Chicken_(game)
I certainly can't find any reference to it in the documentation.
- ajax
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