drm/vc4: hdmi: Adjust HSM clock rate depending on pixel rate

The HSM clock needs to be setup at around 110% of the pixel rate. This
was done previously by setting the clock rate to 148.5MHz * 108% at
probe time and only check in mode_valid whether the mode pixel clock was
under 148.5MHz or not.

However, with 4k we need to change that frequency to a higher frequency
than 148.5MHz.

Let's change that logic a bit by setting the clock rate of the HSM clock
to the pixel rate at encoder_enable time. This would work for the
BCM2711 that support 4k resolutions and has a clock that can provide it,
but we still have to take care of a 4k panel plugged on a BCM283x SoCs
that wouldn't be able to use those modes, so let's define the limit in
the variant.

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

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 7b0ad9c..4cc42de 100644 (file)
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -52,7 +52,6 @@
 #include "vc4_hdmi_regs.h"
 #include "vc4_regs.h"
 
-#define HSM_CLOCK_FREQ 163682864
 #define CEC_CLOCK_FREQ 40000
 
 static int vc4_hdmi_debugfs_regs(struct seq_file *m, void *unused)
@@ -329,6 +328,7 @@ static void vc4_hdmi_encoder_disable(struct drm_encoder *encoder)
        HDMI_WRITE(HDMI_VID_CTL,
                   HDMI_READ(HDMI_VID_CTL) & ~VC4_HD_VID_CTL_ENABLE);
 
+       clk_disable_unprepare(vc4_hdmi->hsm_clock);
        clk_disable_unprepare(vc4_hdmi->pixel_clock);
 
        ret = pm_runtime_put(&vc4_hdmi->pdev->dev);
@@ -426,6 +426,7 @@ static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder)
        struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder);
        struct vc4_hdmi_encoder *vc4_encoder = to_vc4_hdmi_encoder(encoder);
        bool debug_dump_regs = false;
+       unsigned long pixel_rate, hsm_rate;
        int ret;
 
        ret = pm_runtime_get_sync(&vc4_hdmi->pdev->dev);
@@ -434,9 +435,8 @@ static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder)
                return;
        }
 
-       ret = clk_set_rate(vc4_hdmi->pixel_clock,
-                          mode->clock * 1000 *
-                          ((mode->flags & DRM_MODE_FLAG_DBLCLK) ? 2 : 1));
+       pixel_rate = mode->clock * 1000 * ((mode->flags & DRM_MODE_FLAG_DBLCLK) ? 2 : 1);
+       ret = clk_set_rate(vc4_hdmi->pixel_clock, pixel_rate);
        if (ret) {
                DRM_ERROR("Failed to set pixel clock rate: %d\n", ret);
                return;
@@ -448,6 +448,24 @@ static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder)
                return;
        }
 
+       /*
+        * The HSM rate needs to be at 108% of the pixel clock, with a
+        * minimum of 108MHz.
+        */
+       hsm_rate = max_t(unsigned long, 108000000, (pixel_rate / 100) * 108);
+       ret = clk_set_rate(vc4_hdmi->hsm_clock, hsm_rate);
+       if (ret) {
+               DRM_ERROR("Failed to set HSM clock rate: %d\n", ret);
+               return;
+       }
+
+       ret = clk_prepare_enable(vc4_hdmi->hsm_clock);
+       if (ret) {
+               DRM_ERROR("Failed to turn on HSM clock: %d\n", ret);
+               clk_disable_unprepare(vc4_hdmi->pixel_clock);
+               return;
+       }
+
        if (vc4_hdmi->variant->reset)
                vc4_hdmi->variant->reset(vc4_hdmi);
 
@@ -578,7 +596,9 @@ vc4_hdmi_encoder_mode_valid(struct drm_encoder *encoder,
         * Additionally, the AXI clock needs to be at least 25% of
         * pixel clock, but HSM ends up being the limiting factor.
         */
-       if (mode->clock > HSM_CLOCK_FREQ / (1000 * 101 / 100))
+       struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder);
+
+       if ((mode->clock * 1000) > vc4_hdmi->variant->max_pixel_clock)
                return MODE_CLOCK_HIGH;
 
        return MODE_OK;
@@ -1353,23 +1373,6 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data)
                return -EPROBE_DEFER;
        }
 
-       /* This is the rate that is set by the firmware.  The number
-        * needs to be a bit higher than the pixel clock rate
-        * (generally 148.5Mhz).
-        */
-       ret = clk_set_rate(vc4_hdmi->hsm_clock, HSM_CLOCK_FREQ);
-       if (ret) {
-               DRM_ERROR("Failed to set HSM clock rate: %d\n", ret);
-               goto err_put_i2c;
-       }
-
-       ret = clk_prepare_enable(vc4_hdmi->hsm_clock);
-       if (ret) {
-               DRM_ERROR("Failed to turn on HDMI state machine clock: %d\n",
-                         ret);
-               goto err_put_i2c;
-       }
-
        /* Only use the GPIO HPD pin if present in the DT, otherwise
         * we'll use the HDMI core's register.
         */
@@ -1427,9 +1430,7 @@ err_destroy_conn:
 err_destroy_encoder:
        vc4_hdmi_encoder_destroy(encoder);
 err_unprepare_hsm:
-       clk_disable_unprepare(vc4_hdmi->hsm_clock);
        pm_runtime_disable(dev);
-err_put_i2c:
        put_device(&vc4_hdmi->ddc->dev);
 
        return ret;
@@ -1452,7 +1453,6 @@ static void vc4_hdmi_unbind(struct device *dev, struct device *master,
        vc4_hdmi_connector_destroy(&vc4_hdmi->connector);
        vc4_hdmi_encoder_destroy(&vc4_hdmi->encoder.base.base);
 
-       clk_disable_unprepare(vc4_hdmi->hsm_clock);
        pm_runtime_disable(dev);
 
        put_device(&vc4_hdmi->ddc->dev);
@@ -1475,6 +1475,7 @@ static int vc4_hdmi_dev_remove(struct platform_device *pdev)
 }
 
 static const struct vc4_hdmi_variant bcm2835_variant = {
+       .max_pixel_clock        = 148500000,
        .audio_available        = true,
        .cec_available          = true,
        .registers              = vc4_hdmi_fields,

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.h b/drivers/gpu/drm/vc4/vc4_hdmi.h
index cbb1d3a..ee97532 100644 (file)
--- a/drivers/gpu/drm/vc4/vc4_hdmi.h
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.h
@@ -38,6 +38,9 @@ struct vc4_hdmi_variant {
        /* Set to true when the CEC support is available */
        bool cec_available;
 
+       /* Maximum pixel clock supported by the controller (in Hz) */
+       unsigned long long max_pixel_clock;
+
        /* List of the registers available on that variant */
        const struct vc4_hdmi_register *registers;