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Message-Id: <20170317234131.23621-1-eric@anholt.net> Date: Fri, 17 Mar 2017 16:41:30 -0700 From: Eric Anholt <eric@...olt.net> To: dri-devel@...ts.freedesktop.org Cc: linux-kernel@...r.kernel.org, Eric Anholt <eric@...olt.net> Subject: [PATCH 1/2] drm/vc4: Fix DSI T_INIT timing. The DPHY spec requires a much larger T_INIT than I was specifying before. In the absence of clear specs from the slave of what their timing is, just use the value that the firmware was using. Signed-off-by: Eric Anholt <eric@...olt.net> --- drivers/gpu/drm/vc4/vc4_dsi.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c index 160f981d1cf4..3bad8bad32a2 100644 --- a/drivers/gpu/drm/vc4/vc4_dsi.c +++ b/drivers/gpu/drm/vc4/vc4_dsi.c @@ -1094,7 +1094,17 @@ static void vc4_dsi_encoder_enable(struct drm_encoder *encoder) DSI_HS_DLT4_TRAIL) | VC4_SET_FIELD(0, DSI_HS_DLT4_ANLAT)); - DSI_PORT_WRITE(HS_DLT5, VC4_SET_FIELD(dsi_hs_timing(ui_ns, 1000, 5000), + /* T_INIT is how long STOP is driven after power-up to + * indicate to the slave (also coming out of power-up) that + * master init is complete, and should be greater than the + * maximum of two value: T_INIT,MASTER and T_INIT,SLAVE. The + * D-PHY spec gives a minimum 100us for T_INIT,MASTER and + * T_INIT,SLAVE, while allowing protocols on top of it to give + * greater minimums. The vc4 firmware uses an extremely + * conservative 5ms, and we maintain that here. + */ + DSI_PORT_WRITE(HS_DLT5, VC4_SET_FIELD(dsi_hs_timing(ui_ns, + 5 * 1000 * 1000, 0), DSI_HS_DLT5_INIT)); DSI_PORT_WRITE(HS_DLT6, -- 2.11.0
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