Re: [PATCH RESEND 10/17] drm/spacemit: add Saturn DPU KMS pipeline

[Philipp Zabel]

On Sa, 2026-07-25 at 00:51 -0400, Cody Kang via B4 Relay wrote:
> From: Cody Kang <codykang.hk@xxxxxxxxx>
> 
> Add the atomic KMS implementation on top of the hardware backend: one
> CRTC and one primary plane per DPU instance. atomic_check validates
> the plane rectangle 1:1 against the mode and sizes the per-channel FBC
> line buffer; atomic commit builds the cmdlist batches, maps the
> framebuffer through the DMMU and arms the cfg-ready handshake, with
> vblank events driven from the DPU interrupt.
> 
> Signed-off-by: Cody Kang <codykang.hk@xxxxxxxxx>
> ---
>  drivers/gpu/drm/spacemit/spacemit_crtc.c   | 815 +++++++++++++++++++++++++++++
>  drivers/gpu/drm/spacemit/spacemit_planes.c | 376 +++++++++++++
>  2 files changed, 1191 insertions(+)
> 
> diff --git a/drivers/gpu/drm/spacemit/spacemit_crtc.c b/drivers/gpu/drm/spacemit/spacemit_crtc.c
> new file mode 100644
> index 000000000000..b75ff6320501
> --- /dev/null
> +++ b/drivers/gpu/drm/spacemit/spacemit_crtc.c
> @@ -0,0 +1,815 @@
[...]
> +/*
> + * The assert and deassert orders are not mirror images: the hardware wants
> + * these.
> + */
> +static void dpu_reset_assert(struct device *dev, const char *name,
> +			     struct reset_control *rstc)
> +{
> +	int ret = reset_control_assert(rstc);
> +
> +	if (ret)
> +		dev_warn(dev, "failed to assert %s reset: %d\n", name, ret);
> +}
> +
> +static void dpu_reset_deassert(struct device *dev, const char *name,
> +			       struct reset_control *rstc)
> +{
> +	int ret = reset_control_deassert(rstc);
> +
> +	if (ret)
> +		dev_warn(dev, "failed to deassert %s reset: %d\n", name, ret);
> +}
> +
> +static int dpu_pm_suspend(struct device *dev)
> +{
> +	struct spacemit_drm_private *priv = dev_get_drvdata(dev);
> +	struct spacemit_crtc *a_crtc = priv->a_crtc;
> +
> +	/*
> +	 * Assert before gating: a reset asserted into an already-gated block
> +	 * has no clock edges to propagate on and leaves the register file
> +	 * untouched.
> +	 */
> +	dpu_reset_assert(dev, "lcd", a_crtc->lcd_reset);
> +	dpu_reset_assert(dev, "esc", a_crtc->esc_reset);
> +	dpu_reset_assert(dev, "mclk", a_crtc->mclk_reset);

It looks like these three are mirrored, and could be handled by
reset_control_bulk_assert/deassert().

> +	dpu_reset_assert(dev, "aclk", a_crtc->aclk_reset);
> +	dpu_reset_assert(dev, "dsc", a_crtc->dsc_reset);
> +	usleep_range(10000, 20000);
> +
> +	if (a_crtc->core && a_crtc->core->disable_clk)
> +		a_crtc->core->disable_clk(a_crtc);
> +
> +	return 0;
> +}
> +
> +static int dpu_pm_resume(struct device *dev)
> +{
> +	struct spacemit_drm_private *priv = dev_get_drvdata(dev);
> +	struct spacemit_crtc *a_crtc = priv->a_crtc;
> +
> +	dpu_reset_deassert(dev, "mclk", a_crtc->mclk_reset);
> +	dpu_reset_deassert(dev, "esc", a_crtc->esc_reset);
> +	dpu_reset_deassert(dev, "lcd", a_crtc->lcd_reset);
> +	dpu_reset_deassert(dev, "aclk", a_crtc->aclk_reset);
> +	dpu_reset_deassert(dev, "dsc", a_crtc->dsc_reset);
> +
> +	if (a_crtc->core && a_crtc->core->enable_clk)
> +		a_crtc->core->enable_clk(a_crtc);
> +
> +	return 0;
> +}

regards
Philipp