Re: [PATCH v1 5/6] drm/rockchip: dw_hdmi: introduce the VPLL clock setting

From: Yakir Yang
Date: Wed Jul 13 2016 - 03:46:16 EST


On 07/12/2016 10:27 PM, Heiko Stübner wrote:
Hi Yakir,

Am Montag, 11. Juli 2016, 19:05:49 schrieb Yakir Yang:
For RK3399 HDMI, there is an external clock need for HDMI PHY,
and it should keep the same clock rate with VOP DCLK.

VPLL have supported the clock for HDMI PHY, but there is no
clock divider bewteen VPLL and HDMI PHY. So we need to set the
VPLL rate manually in HDMI driver.
I don't think reserving the vpll for the hdmi at all times is the right way to

While I do agree that reserving the VPLL (and NPLL on the rk3288) for graphics
use looks like the right way, I think the core Rockchip drm driver should be
responsible for managing it and also for deciding which output encoder gets to
use it.
While true that on the Chromebook device-types the edp is static and hdmi
needs the broad range of dynamic frequencies, this is not necessarily the case
for all future device types and/or socs.

In the other thread we discussed adding that as rockchip,dclk-pll = <&...>; to
the base display-subsystem node, Doug didn't manage to find time to respond yet
though - and is on vacation right now.

Great idea. Let a separate drm-pll driver to maintain all connector's clock requirement.

I still believe that would be the best solution :-) .

That property could list 1 or even 2 plls, depending on the soc or board
layout - maybe someone frees up the cpll in some special layout or something.
If none are listed, then the drm driver would need to cope with its available

Implementation-wise you could even still keep your shortcut until we encounter
a device with different , let the drm use the pll for hdmi only until someone
comes up with a better concept, but still the binding should be correct and
versatile from the start.

Someone should start to prepare the drm core pll driver, it's great idea.

- Yakir


.../bindings/display/rockchip/dw_hdmi-rockchip.txt | 3 ++-
drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c | 25
+++++++++++++++++++++- 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git
index 4e573d2..4e23ca4 100644
@@ -17,7 +17,8 @@ Required properties:

Optional properties
- ddc-i2c-bus: phandle of an I2C controller used for DDC EDID probing
-- clocks, clock-names: phandle to the HDMI CEC clock, name should be "cec"
+- clocks, clock-names: phandle to the HDMI CEC clock, name should be "cec",
+ phandle to the VPLL clock, name should be "vpll".

hdmi: hdmi@ff980000 {
diff --git a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c index 329099b..701bb73 100644
--- a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
+++ b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
@@ -7,10 +7,12 @@
* (at your option) any later version.

+#include <linux/clk.h>
+#include <linux/mfd/syscon.h>
#include <linux/module.h>
#include <linux/platform_device.h>
-#include <linux/mfd/syscon.h>
#include <linux/regmap.h>
#include <drm/drm_of.h>
#include <drm/drmP.h>
#include <drm/drm_crtc_helper.h>
@@ -33,6 +35,7 @@ struct rockchip_hdmi {
struct regmap *regmap;
struct drm_encoder encoder;
enum dw_hdmi_devtype dev_type;
+ struct clk *vpll_clk;

#define to_rockchip_hdmi(x) container_of(x, struct rockchip_hdmi, x)
@@ -145,6 +148,7 @@ static const struct dw_hdmi_phy_config
rockchip_phy_config[] = { static int rockchip_hdmi_parse_dt(struct
rockchip_hdmi *hdmi)
struct device_node *np = hdmi->dev->of_node;
+ int ret;

hdmi->regmap = syscon_regmap_lookup_by_phandle(np, "rockchip,grf");
if (IS_ERR(hdmi->regmap)) {
@@ -152,6 +156,22 @@ static int rockchip_hdmi_parse_dt(struct rockchip_hdmi
*hdmi) return PTR_ERR(hdmi->regmap);

+ hdmi->vpll_clk = devm_clk_get(hdmi->dev, "vpll");
+ if (PTR_ERR(hdmi->vpll_clk) == -ENOENT) {
+ hdmi->vpll_clk = NULL;
+ } else if (PTR_ERR(hdmi->vpll_clk) == -EPROBE_DEFER) {
+ return -EPROBE_DEFER;
+ } else if (IS_ERR(hdmi->vpll_clk)) {
+ dev_err(hdmi->dev, "failed to get grf clock\n");
+ return PTR_ERR(hdmi->vpll_clk);
+ }
+ ret = clk_prepare_enable(hdmi->vpll_clk);
+ if (ret) {
+ dev_err(hdmi->dev, "Failed to enable HDMI vpll: %d\n", ret);
+ return ret;
+ }
return 0;

@@ -194,6 +214,9 @@ static void dw_hdmi_rockchip_encoder_mode_set(struct
drm_encoder *encoder, struct drm_display_mode *mode,
struct drm_display_mode *adj_mode)
+ struct rockchip_hdmi *hdmi = to_rockchip_hdmi(encoder);
+ clk_set_rate(hdmi->vpll_clk, adj_mode->clock * 1000);

static void dw_hdmi_rockchip_encoder_enable(struct drm_encoder *encoder)