Historically, the HSM clock for BCM2835 was fixed at 163.7 MHz. Since
the pixel clock had to be at least 1% below the HSM clock, it was capped
at 162 MHz.
Since commit cd4cb49dc5bb ("drm/vc4: hdmi: Adjust HSM clock rate
depending on pixel rate"), the HSM clock rate is set to pixel clock *
101 / 100. For a 165 MHz pixel clock, this gives an HSM rate of 166.65
MHz, which, per Dave Stevenson, the hardware can handle without issues.
Increase the max pixel clock to 165 MHz, which matches the maximum TMDS
character rate of HDMI 1.0 through 1.2.
Suggested-by: Dave Stevenson <[email protected]>
Signed-off-by: Cristian Ciocaltea <[email protected]>
---
drivers/gpu/drm/vc4/vc4_hdmi.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 8e4623ccc4f8..e61f1b694dbe 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -1507,7 +1507,7 @@ static void vc4_hdmi_encoder_pre_crtc_configure(struct
drm_encoder *encoder,
* users are able to use pixel clocks closer to HSM's, namely for
* 1920x1200@60Hz. So it was decided to have leave a 1% margin between
* both clocks. Which, for RPi0-3 implies a maximum pixel clock of
- * 162MHz.
+ * 165MHz.
*
* Additionally, the AXI clock needs to be at least 25% of
* pixel clock, but HSM ends up being the limiting factor.
@@ -3363,7 +3363,7 @@ static const struct vc4_hdmi_variant bcm2835_variant = {
.encoder_type = VC4_ENCODER_TYPE_HDMI0,
.debugfs_name = "hdmi_regs",
.card_name = "vc4-hdmi",
- .max_pixel_clock = 162000000,
+ .max_pixel_clock = HDMI_1_0_TMDS_CHAR_RATE_MAX_HZ,
.registers = vc4_hdmi_fields,
.num_registers = ARRAY_SIZE(vc4_hdmi_fields),
--
2.55.0
