| Message ID | 20181127134057.15659-1-linus.walleij@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] drm/panel: Set max rate for Ilitek ILI9881C | expand |
On Tue, Nov 27, 2018 at 02:40:57PM +0100, Linus Walleij wrote: > After adding the hs_rate and lp_rate fields to the DSI device > we need to populate these accordingly so display drivers can > respect them. > > This figure for HS rate comes from the ILI9881C manual, the > calculation is explained in the comment. > > Cc: Daniel Vetter <daniel.vetter@ffwll.ch> > Cc: Andrzej Hajda <a.hajda@samsung.com> > Acked-by: Maxime Ripard <maxime.ripard@bootlin.com> > Signed-off-by: Linus Walleij <linus.walleij@linaro.org> > --- > ChangeLov v2->v3: > - Fix up the HS speed to 275 MHz, as the speed is double > data rate. > ChangeLog v1->v2: > - Add LP speed after Andrzej's observation. > - Collect Maxime's ACK (hope it's fine also with the LP speed) > --- > drivers/gpu/drm/panel/panel-ilitek-ili9881c.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) Acked-by: Thierry Reding <treding@nvidia.com>
On 27.11.2018 14:40, Linus Walleij wrote: > After adding the hs_rate and lp_rate fields to the DSI device > we need to populate these accordingly so display drivers can > respect them. > > This figure for HS rate comes from the ILI9881C manual, the > calculation is explained in the comment. > > Cc: Daniel Vetter <daniel.vetter@ffwll.ch> > Cc: Andrzej Hajda <a.hajda@samsung.com> > Acked-by: Maxime Ripard <maxime.ripard@bootlin.com> > Signed-off-by: Linus Walleij <linus.walleij@linaro.org> > --- > ChangeLov v2->v3: > - Fix up the HS speed to 275 MHz, as the speed is double > data rate. > ChangeLog v1->v2: > - Add LP speed after Andrzej's observation. > - Collect Maxime's ACK (hope it's fine also with the LP speed) > --- > drivers/gpu/drm/panel/panel-ilitek-ili9881c.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c > index 3ad4a46c4e94..8c00193c2400 100644 > --- a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c > +++ b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c > @@ -465,6 +465,21 @@ static int ili9881c_dsi_probe(struct mipi_dsi_device *dsi) > dsi->mode_flags = MIPI_DSI_MODE_VIDEO_SYNC_PULSE; > dsi->format = MIPI_DSI_FMT_RGB888; > dsi->lanes = 4; > + /* > + * The datasheet (table 39) specifies "limited clock channel speed" > + * for 4 lanes as 550 Mbps per lane for RGB888. As this is 4 bits at > + * the time, I don't understand the part "As this is 4 bits at the time" ? Where it came from? I guess the only calculation should be due to double-data-rate: hs_rate = 550Mbps / 2BitsPerTick > at double data rate the maximum HS frequency should > + * be: > + * 550/4 * 2 = 275 MHz. > + */ > + dsi->hs_rate = 275000000; > + /* > + * Table 42 says: "Length of LP-00, LP-01, LP-10 or LP-11 periods": > + * min 50ns, max 75ns. 1/50ns = max LPM rate = 20.000.000Hz. > + * Since LP transmissions are to periods per bit, this should be Again: s/to/two/ Regards Andrzej > + * 10 MHz. > + */ > + dsi->lp_rate = 10000000; > > return mipi_dsi_attach(dsi); > }
diff --git a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c index 3ad4a46c4e94..8c00193c2400 100644 --- a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c +++ b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c @@ -465,6 +465,21 @@ static int ili9881c_dsi_probe(struct mipi_dsi_device *dsi) dsi->mode_flags = MIPI_DSI_MODE_VIDEO_SYNC_PULSE; dsi->format = MIPI_DSI_FMT_RGB888; dsi->lanes = 4; + /* + * The datasheet (table 39) specifies "limited clock channel speed" + * for 4 lanes as 550 Mbps per lane for RGB888. As this is 4 bits at + * the time, at double data rate the maximum HS frequency should + * be: + * 550/4 * 2 = 275 MHz. + */ + dsi->hs_rate = 275000000; + /* + * Table 42 says: "Length of LP-00, LP-01, LP-10 or LP-11 periods": + * min 50ns, max 75ns. 1/50ns = max LPM rate = 20.000.000Hz. + * Since LP transmissions are to periods per bit, this should be + * 10 MHz. + */ + dsi->lp_rate = 10000000; return mipi_dsi_attach(dsi); }