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SubjectRE: [PATCH v5 4/6] drm: rcar-du: lvds: Allow for even and odd pixels swap
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Hi Laurent,

Thank you for your feedback!

> From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Sent: 16 December 2019 21:35
> Subject: Re: [PATCH v5 4/6] drm: rcar-du: lvds: Allow for even and odd pixels swap
>
> Hi Fabrizio,
>
> Thank you for the patch.
>
> On Mon, Dec 16, 2019 at 08:12:32PM +0000, Fabrizio Castro wrote:
> > DT properties dual-lvds-even-pixels and dual-lvds-odd-pixels
> > can be used to work out if the driver needs to swap even
> > and odd pixels around.
> >
> > This patch makes use of the return value from function
> > drm_of_lvds_get_dual_link_pixel_order to determine if we
> > need to swap odd and even pixels around for things to work
> > properly.
> >
> > Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
> >
> > ---
> > v4->v5:
> > * Addressed comments from Laurent's review
> >
> > v3->v4:
> > * New patch extracted from patch:
> > "drm: rcar-du: lvds: Add dual-LVDS panels support"
> > ---
> > drivers/gpu/drm/rcar-du/rcar_lvds.c | 67 +++++++++++++++++++++++++++++--------
> > 1 file changed, 53 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/rcar-du/rcar_lvds.c b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> > index 3eb208e..c6a38c3 100644
> > --- a/drivers/gpu/drm/rcar-du/rcar_lvds.c
> > +++ b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> > @@ -37,6 +37,12 @@ enum rcar_lvds_mode {
> > RCAR_LVDS_MODE_VESA = 4,
> > };
> >
> > +enum rcar_lvds_link_type {
> > + RCAR_LVDS_SINGLE_LINK = 0,
> > + RCAR_LVDS_DUAL_LINK_EVEN_ODD_PIXELS = 1,
> > + RCAR_LVDS_DUAL_LINK_ODD_EVEN_PIXELS = 2,
> > +};
> > +
> > #define RCAR_LVDS_QUIRK_LANES BIT(0) /* LVDS lanes 1 and 3 inverted */
> > #define RCAR_LVDS_QUIRK_GEN3_LVEN BIT(1) /* LVEN bit needs to be set on R8A77970/R8A7799x */
> > #define RCAR_LVDS_QUIRK_PWD BIT(2) /* PWD bit available (all of Gen3 but E3) */
> > @@ -67,7 +73,7 @@ struct rcar_lvds {
> > } clocks;
> >
> > struct drm_bridge *companion;
> > - bool dual_link;
> > + enum rcar_lvds_link_type dual_link;
>
> Do you think we should rename this to link_type (and test for
> lvds->link_type != RCAR_LVDS_SINGLE_LINK) instead of lvds->dual_link) ?
> Apart from that,

I'll send v6 to address that. I will also rebase on top of:
https://patchwork.kernel.org/patch/11295991/
and will use that as a dependency for v6

Cheers,
Fab

>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>
> > };
> >
> > #define bridge_to_rcar_lvds(b) \
> > @@ -484,12 +490,31 @@ static void rcar_lvds_atomic_enable(struct drm_bridge *bridge,
> > rcar_lvds_write(lvds, LVDCHCR, lvdhcr);
> >
> > if (lvds->info->quirks & RCAR_LVDS_QUIRK_DUAL_LINK) {
> > - /*
> > - * Configure vertical stripe based on the mode of operation of
> > - * the connected device.
> > - */
> > - rcar_lvds_write(lvds, LVDSTRIPE,
> > - lvds->dual_link ? LVDSTRIPE_ST_ON : 0);
> > + u32 lvdstripe = 0;
> > +
> > + if (lvds->dual_link) {
> > + /*
> > + * By default we generate even pixels from the primary
> > + * encoder and odd pixels from the companion encoder.
> > + * Swap pixels around if the sink requires odd pixels
> > + * from the primary encoder and even pixels from the
> > + * companion encoder.
> > + */
> > + bool swap_pixels = lvds->dual_link ==
> > + RCAR_LVDS_DUAL_LINK_ODD_EVEN_PIXELS;
> > +
> > + /*
> > + * Configure vertical stripe since we are dealing with
> > + * an LVDS dual-link connection.
> > + *
> > + * ST_SWAP is reserved for the companion encoder, only
> > + * set it in the primary encoder.
> > + */
> > + lvdstripe = LVDSTRIPE_ST_ON
> > + | (lvds->companion && swap_pixels ?
> > + LVDSTRIPE_ST_SWAP : 0);
> > + }
> > + rcar_lvds_write(lvds, LVDSTRIPE, lvdstripe);
> > }
> >
> > /*
> > @@ -716,15 +741,26 @@ static int rcar_lvds_parse_dt_companion(struct rcar_lvds *lvds)
> > of_node_put(port0);
> > of_node_put(port1);
> >
> > - if (dual_link >= DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS)
> > - lvds->dual_link = true;
> > - else if (lvds->next_bridge && lvds->next_bridge->timings)
> > + switch (dual_link) {
> > + case DRM_LVDS_DUAL_LINK_ODD_EVEN_PIXELS:
> > + lvds->dual_link = RCAR_LVDS_DUAL_LINK_ODD_EVEN_PIXELS;
> > + break;
> > + case DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS:
> > + lvds->dual_link = RCAR_LVDS_DUAL_LINK_EVEN_ODD_PIXELS;
> > + break;
> > + default:
> > /*
> > * Early dual-link bridge specific implementations populate the
> > - * timings field of drm_bridge, read the dual_link flag off the
> > - * bridge directly for backward compatibility.
> > + * timings field of drm_bridge. If the flag is set, we assume
> > + * that we are expected to generate even pixels from the primary
> > + * encoder, and odd pixels from the companion encoder.
> > */
> > - lvds->dual_link = lvds->next_bridge->timings->dual_link;
> > + if (lvds->next_bridge && lvds->next_bridge->timings &&
> > + lvds->next_bridge->timings->dual_link)
> > + lvds->dual_link = RCAR_LVDS_DUAL_LINK_EVEN_ODD_PIXELS;
> > + else
> > + lvds->dual_link = RCAR_LVDS_SINGLE_LINK;
> > + }
> >
> > if (!lvds->dual_link) {
> > dev_dbg(dev, "Single-link configuration detected\n");
> > @@ -741,6 +777,9 @@ static int rcar_lvds_parse_dt_companion(struct rcar_lvds *lvds)
> > "Dual-link configuration detected (companion encoder %pOF)\n",
> > companion);
> >
> > + if (lvds->dual_link == RCAR_LVDS_DUAL_LINK_ODD_EVEN_PIXELS)
> > + dev_dbg(dev, "Data swapping required\n");
> > +
> > /*
> > * FIXME: We should not be messing with the companion encoder private
> > * data from the primary encoder, we should rather let the companion
> > @@ -751,7 +790,7 @@ static int rcar_lvds_parse_dt_companion(struct rcar_lvds *lvds)
> > * for the time being.
> > */
> > companion_lvds = bridge_to_rcar_lvds(lvds->companion);
> > - companion_lvds->dual_link = true;
> > + companion_lvds->dual_link = lvds->dual_link;
> >
> > done:
> > of_node_put(companion);
>
> --
> Regards,
>
> Laurent Pinchart
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