Re: [PATCH 04/10] drm/sun4i: sun6i_mipi_dsi: Setup burst mode

Maxime Ripard
2018-11-05T10:45:32Z

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On Sat, Nov 03, 2018 at 03:38:54PM +0530, Jagan Teki wrote:
> Setting up burst mode display would require to compute
> - Horizontal timing edge values to fill burst drq register
> - Line, sync values to fill burst line register
>
> Since there is no direct documentation for these computations
> the edge and line formulas are taken from BSP code
> (in drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/de_dsi.c)
> line_num = panel->lcd_ht*dsi_pixel_bits[panel->lcd_dsi_format]/
> (8*panel->lcd_dsi_lane);
> edge1 = sync_point+(panel->lcd_x+panel->lcd_hbp+20)*
> dsi_pixel_bits[panel->lcd_dsi_format] /(8*panel->lcd_dsi_lane);
> edge1 = (edge1>line_num)?line_num:edge1;
> edge0 = edge1+(panel->lcd_x+40)*tcon_div/8;
> edge0 = (edge0>line_num)?(edge0-line_num):1;
>
> Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> ---
> drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 48 +++++++++++++++++++++-----
> 1 file changed, 40 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> index 4965b2c71e4c..b6c01891df36 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> @@ -375,20 +375,52 @@ static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi,
> struct drm_display_mode *mode)
> {
> struct mipi_dsi_device *device = dsi->device;
> + unsigned int Bpp = mipi_dsi_pixel_format_to_bpp(device->format);
> + u32 line_num, edge0, edge1, hact_sync_bp;
> + u32 sync_point, tcon_div;
> u32 val = 0;
>
> - if ((mode->hsync_start - mode->hdisplay) > 20) {
> - /* Maaaaaagic */
> - u16 drq = (mode->hsync_start - mode->hdisplay) - 20;
> + if (device->mode_flags != MIPI_DSI_MODE_VIDEO_BURST) {
> + if ((mode->hsync_start - mode->hdisplay) > 20) {
> + /* Maaaaaagic */
> + u16 drq = (mode->hsync_start - mode->hdisplay) - 20;
>
> - drq *= mipi_dsi_pixel_format_to_bpp(device->format);
> - drq /= 32;
> + drq *= Bpp;
> + drq /= 32;
>
> - val = (SUN6I_DSI_TCON_DRQ_ENABLE_MODE |
> - SUN6I_DSI_TCON_DRQ_SET(drq));
> + val = (SUN6I_DSI_TCON_DRQ_ENABLE_MODE |
> + SUN6I_DSI_TCON_DRQ_SET(drq));
> + }
> +
> + regmap_write(dsi->regs, SUN6I_DSI_TCON_DRQ_REG, val);
> +
> + return;
> }

Having functions to compute drq, the line_number and so on would help
the readibility a lot.

> - regmap_write(dsi->regs, SUN6I_DSI_TCON_DRQ_REG, val);
> + sync_point = 40;
> + tcon_div = 8; /* FIXME need to retrive the divider from TCON */

Then do it. Especially since you have exactly 0 guarantee of the
divider being 8.

(also, s/retrive/retrieve/)

> +
> + line_num = mode->htotal * Bpp / (8 * device->lanes);
> + /* Horizental timings duration excluding front porch */

Horizontal

Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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