On Fri, Sep 08, 2017 at 07:18:55PM +0530, Vidya Srinivas wrote:
> From: Uma Shankar <uma.shankar@xxxxxxxxx>
>
> For gen9 platforms, dsi timings are driven from port instead of pipe
> (unlike ddi). Thus, we can't rely on pipe registers to get the timing
> information. Even scanline register read will not be functional.
> This is causing vblank evasion logic to fail since it relies on
> scanline, causing atomic update failure warnings.
>
> This patch uses pipe framestamp and current timestamp registers
> to calculate scanline. This is an indirect way to get the scanline.
> It helps resolve atomic update failure for gen9 dsi platforms.
>
> Signed-off-by: Uma Shankar <uma.shankar@xxxxxxxxx>
> Signed-off-by: Chandra Konduru <chandra.konduru@xxxxxxxxx>
> Signed-off-by: Vidya Srinivas <vidya.srinivas@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_drv.h | 2 ++
> drivers/gpu/drm/i915/i915_irq.c | 5 +++++
> drivers/gpu/drm/i915/i915_reg.h | 3 +++
> drivers/gpu/drm/i915/intel_dsi.c | 46 ++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 56 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index d07d110..4213b54 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -4077,6 +4077,8 @@ void intel_sbi_write(struct drm_i915_private *dev_priv, u16 reg, u32 value,
> u32 vlv_flisdsi_read(struct drm_i915_private *dev_priv, u32 reg);
> void vlv_flisdsi_write(struct drm_i915_private *dev_priv, u32 reg, u32 val);
>
> +u32 bxt_dsi_get_scanline(struct intel_crtc *crtc);
> +
> /* intel_dpio_phy.c */
> void bxt_port_to_phy_channel(struct drm_i915_private *dev_priv, enum port port,
> enum dpio_phy *phy, enum dpio_channel *ch);
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 5d391e6..31aa7f0 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -781,6 +781,7 @@ static int __intel_get_crtc_scanline(struct intel_crtc *crtc)
> struct drm_vblank_crtc *vblank;
> enum pipe pipe = crtc->pipe;
> int position, vtotal;
> + enum transcoder cpu_transcoder;
>
> if (!crtc->active)
> return -1;
> @@ -792,6 +793,10 @@ static int __intel_get_crtc_scanline(struct intel_crtc *crtc)
> if (mode->flags & DRM_MODE_FLAG_INTERLACE)
> vtotal /= 2;
>
> + cpu_transcoder = crtc->config->cpu_transcoder;
Humm. Would be nice to be able to do this without adding more
crtc->config uses. We're pretty much trying to get rid of that guy.
> + if (IS_BROXTON(dev_priv) && transcoder_is_dsi(cpu_transcoder))
> + return bxt_dsi_get_scanline(crtc);
> +
> if (IS_GEN2(dev_priv))
> position = I915_READ_FW(PIPEDSL(pipe)) & DSL_LINEMASK_GEN2;
> else
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 9a73ea0..54582de 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -8802,6 +8802,9 @@ enum skl_power_gate {
> #define MIPIO_TXESC_CLK_DIV2 _MMIO(0x160008)
> #define GLK_TX_ESC_CLK_DIV2_MASK 0x3FF
>
> +#define BXT_TIMESTAMP_CTR _MMIO(0x44070)
> +#define BXT_PIPE_FRMTMSTMP_A _MMIO(0x70048)
Please add proper parametrized define that works for all pipes.
> +
> /* BXT MIPI clock controls */
> #define BXT_MAX_VAR_OUTPUT_KHZ 39500
>
> diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
> index 2a0f5d3..d145ba4 100644
> --- a/drivers/gpu/drm/i915/intel_dsi.c
> +++ b/drivers/gpu/drm/i915/intel_dsi.c
> @@ -1621,6 +1621,52 @@ static int intel_dsi_get_modes(struct drm_connector *connector)
> return 1;
> }
>
> +/*
> + * For Gen9 DSI, pipe scanline register will not
> + * work to get the scanline since the timings
> + * are driven from the PORT (unlike DDI encoders).
> + * This function will use Framestamp and current
> + * timestamp registers to calculate the scanline.
> + */
> +u32 bxt_dsi_get_scanline(struct intel_crtc *crtc)
> +{
> + struct drm_device *dev = crtc->base.dev;
> + struct drm_i915_private *dev_priv = to_i915(dev);
> + u32 vrefresh = crtc->base.mode.vrefresh;
> + u32 ulPrevTime, ulCurrTime, vtotal, ulScanlineNo2 = 0;
Please get rid of the hungarian notation.
> + uint_fixed_16_16_t ulScanlineTime;
> +
> + /*
> + * This field provides read back of the display
> + * pipe frame time stamp. The time stamp value
> + * is sampled at every start of vertical blank.
> + */
> + ulPrevTime = I915_READ_FW(BXT_PIPE_FRMTMSTMP_A);
> +
> + /*
> + * The TIMESTAMP_CTR register has the current
> + * time stamp value.
> + */
> + ulCurrTime = I915_READ_FW(BXT_TIMESTAMP_CTR);
> +
> + /* The PORT for DSI will always be 0 since
> + * isolated PORTC cannot be enabled for Gen9
> + * DSI. Hence using PORT_A i.e 0 to extract
> + * the VTOTAL value.
> + */
> + vtotal = I915_READ_FW(BXT_MIPI_TRANS_VTOTAL(0));
This value can be dug out from the hwmode.
> + WARN_ON(!vtotal);
> + if (!vtotal)
> + return ulScanlineNo2;
> +
> + ulScanlineTime = div_fixed16(1000000, vtotal * vrefresh);
> + ulScanlineNo2 = div_round_up_u32_fixed16((ulCurrTime - ulPrevTime),
> + ulScanlineTime);
Something like:
scanline = div_u64(mul_u32_u32(curr - prev, crtc_clock),
1000 * crtc_htotal);
> + ulScanlineNo2 = (ulScanlineNo2 + vtotal) % vtotal;
I think that would have to be something like:
return (scanline + vblank_start) % vtotal;
All in all this looks like a pretty decent approach to the DSI problem.
One concern here is rounding issues and inaccuracies in our
crtc_clock. But since the frame timestamp is sampled at vblank start I
guess we can't accidentally get an answer that's earlier than
vblank_start as long as we really passed vblank start already. That
should make this at least suitable for vblank timestamps. And for the
atomic evade, I guess if we clamp our the scanline before the
+vblank_start such that it never reaches vtotal, we can't be sure that
our vblank evade never indicates that we already reached the start of
vblank prematurely.
So maybe something like:
scaline = div_u64(...);
scanline = min(scanline, vtotal - 1);
return (scanline + vblank_start) % vtotal;
At least that's my thinking atm. Feel free to rip my reasoning to shreds
if you think I'm totally wrong here.
> +
> + return ulScanlineNo2;
> +}
> +
> static void intel_dsi_connector_destroy(struct drm_connector *connector)
> {
> struct intel_connector *intel_connector = to_intel_connector(connector);
> --
> 1.9.1
--
Ville Syrjälä
Intel OTC
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