Re: [PATCH v2 3/4] drm/sun4i: tcon: Support the LVDS Dual-Link on the A20

Hi Maxime,

Thank you for the patch.

On Thu, Jul 30, 2020 at 11:35:03AM +0200, Maxime Ripard wrote:

The A20 can use its second TCON as the secondary LVDS link in a dual-link setup, with the TCON0 being the main link. Extend a bit the parsing code to leverage the DRM dual-link code, register only the LVDS output on the primary TCON, and add the needed bits to setup the TCON properly.

Signed-off-by: Maxime Ripard maxime@cerno.tech

drivers/gpu/drm/sun4i/sun4i_tcon.c | 36 +++++++++++++++++++++++++++++++- drivers/gpu/drm/sun4i/sun4i_tcon.h | 4 +++- 2 files changed, 40 insertions(+)

diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c index d03ad75f9900..ed2abf6eb18b 100644 --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c @@ -487,6 +487,9 @@ static void sun4i_tcon0_mode_set_lvds(struct sun4i_tcon *tcon, else reg |= SUN4I_TCON0_LVDS_IF_DATA_POL_NORMAL;

• if (tcon->lvds_dual_link)

• reg |= SUN4I_TCON0_LVDS_IF_DUAL_LINK;
  

• if (sun4i_tcon_get_pixel_depth(encoder) == 24) reg |= SUN4I_TCON0_LVDS_IF_BITWIDTH_24BITS; else

@@ -896,6 +899,16 @@ static int sun4i_tcon_register_panel(struct drm_device *drm, return sun4i_rgb_init(drm, tcon);

/*

• * Only the TCON0 will be relevant for the LVDS output, so if
  

• * our ID is something else, let's prevent our TCON from
  

• * registering its own LVDS output
  

• */
  

• if (tcon->id) {

• dev_info(dev, "Secondary TCON, disabling panel output");
  

This may worry the user unnecessarily. I'd make it a debug message, or drop it completely, and like reword it a bit as pointed out by Chen-Yu.

• return 0;
  

• }
• /*
  • This can only be made optional since we've had DT
  • nodes without the LVDS reset properties.

@@ -941,6 +954,28 @@ static int sun4i_tcon_register_panel(struct drm_device *drm, return -ENODEV; }

• /*

• * If we don't have a second TCON, we will never be able to do
  

• * dual-link LVDS, so we don't have much more to do.
  

• */
  

• companion = of_parse_phandle(dev->of_node, "allwinner,lvds-companion", 0);

Should there be a patch to add this property to the DT bindings ?

• if (!companion)

• return 0;
  

• /*

• * Let's do a sanity check on the dual-link setup to make sure
  

• * everything is properly described.
  

• */
  

• ret = drm_of_lvds_get_dual_link_pixel_order(dev->of_node, 1, 0,

• 				    companion, 1, 0);
  

• if (ret < 0) {

• dev_err(dev, "Invalid Dual-Link Configuration.\n");
  

• return ret;
  

• }
• dev_info(dev, "Primary TCON, enabling LVDS Dual-Link");
• tcon->lvds_dual_link = true;
• return sun4i_lvds_init(drm, tcon);

}

@@ -1500,6 +1535,7 @@ static const struct sun4i_tcon_quirks sun7i_a20_tcon0_quirks = { };

static const struct sun4i_tcon_quirks sun7i_a20_quirks = {

• .supports_lvds = true,

Should this be split to a separate patch, or at least mentioned in the commit message ?

.has_channel_0 = true, .has_channel_1 = true, .dclk_min_div = 4, diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.h b/drivers/gpu/drm/sun4i/sun4i_tcon.h index cfbf4e6c1679..51c4e09cdd13 100644 --- a/drivers/gpu/drm/sun4i/sun4i_tcon.h +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.h @@ -98,6 +98,7 @@

#define SUN4I_TCON0_LVDS_IF_REG 0x84 #define SUN4I_TCON0_LVDS_IF_EN BIT(31) +#define SUN4I_TCON0_LVDS_IF_DUAL_LINK BIT(30) #define SUN4I_TCON0_LVDS_IF_BITWIDTH_MASK BIT(26) #define SUN4I_TCON0_LVDS_IF_BITWIDTH_18BITS (1 << 26) #define SUN4I_TCON0_LVDS_IF_BITWIDTH_24BITS (0 << 26) @@ -274,6 +275,9 @@ struct sun4i_tcon { /* Associated crtc */ struct sun4i_crtc *crtc;

• /* Is the LVDS link a dual-channel link? */

• bool lvds_dual_link;

• int id;

  /* TCON list management */