[PATCH v9 01/23] clk: rk3568: Mark hclk_vo as critical

Sascha Hauer
2022-03-28T15:15:26Z

Whenever pclk_vo is enabled hclk_vo must be enabled as well. This is
described in the Reference Manual as:

| 2.8.6 NIU Clock gating reliance
|
| A part of niu clocks have a dependence on another niu clock in order to
| sharing the internal bus. When these clocks are in use, another niu
| clock must be opened, and cannot be gated. These clocks and the special
| clock on which they are relied are as following:
|
| Clocks which have dependency The clock which can not be gated
| -----------------------------------------------------------------
| ...
| pclk_vo_niu, hclk_vo_s_niu hclk_vo_niu
| ...

The clock framework doesn't offer a way to enable clock B whenever clock A is
enabled, at least not when B is not an ancestor of A. Workaround this by
marking hclk_vo as critical so it is never disabled. This is suboptimal in
terms of power consumption, but a stop gap solution until the clock framework
has a way to deal with this.

We have this clock tree:

| aclk_vo 2 2 0 300000000 0 0 50000 Y
| aclk_hdcp 0 0 0 300000000 0 0 50000 N
| pclk_vo 2 3 0 75000000 0 0 50000 Y
| pclk_edp_ctrl 0 0 0 75000000 0 0 50000 N
| pclk_dsitx_1 0 0 0 75000000 0 0 50000 N
| pclk_dsitx_0 1 2 0 75000000 0 0 50000 Y
| pclk_hdmi_host 1 2 0 75000000 0 0 50000 Y
| pclk_hdcp 0 0 0 75000000 0 0 50000 N
| hclk_vo 2 5 0 150000000 0 0 50000 Y
| hclk_hdcp 0 0 0 150000000 0 0 50000 N
| hclk_vop 0 2 0 150000000 0 0 50000 N

Without this patch the edp, dsitx, hdmi and hdcp driver would enable their
clocks which then enables pclk_vo, but hclk_vo stays disabled and register
accesses just hang. hclk_vo is enabled by the VOP2 driver, so reproducibility
of this issue depends on the probe order.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---

Notes:
Changes since v8:
- new patch

drivers/clk/rockchip/clk-rk3568.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/clk/rockchip/clk-rk3568.c b/drivers/clk/rockchip/clk-rk3568.c
index 63dfbeeeb06d9..62694d95173ab 100644
--- a/drivers/clk/rockchip/clk-rk3568.c
+++ b/drivers/clk/rockchip/clk-rk3568.c
@@ -1591,6 +1591,7 @@ static const char *const rk3568_cru_critical_clocks[] __initconst = {
"hclk_php",
"pclk_php",
"hclk_usb",
+ "hclk_vo",
};

static const char *const rk3568_pmucru_critical_clocks[] __initconst = {
--
2.30.2