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

Hi Philipp,

On Mon, 27 Jul 2026 09:35:38 +0200, Philipp Zabel wrote:
> On Sa, 2026-07-25 at 00:51 -0400, Cody Kang via B4 Relay wrote:
> > From: Cody Kang <[email protected]>
> >
> > 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 <[email protected]>
> > ---
> >  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().

Thanks for the review. Indeed, reset_control_bulk_deassert()
walking the array in reverse gives exactly the mirrored order the
hardware wants. Will fix in v2.

Cody