[PATCH AUTOSEL 5.10 094/176] drm: xlnx: zynqmp_dpsub: Call pm_runtime_get_sync before setting pixel clock

Sasha Levin
2021-09-09T12:45:41Z

From: Quanyang Wang <quanyang.wang@windriver.com>

[ Upstream commit a19effb6dbe5bd1be77a6d68eba04dba8993ffeb ]

The Runtime PM subsystem will force the device "fd4a0000.zynqmp-display"
to enter suspend state while booting if the following conditions are met:
- the usage counter is zero (pm_runtime_get_sync hasn't been called yet)
- no 'active' children (no zynqmp-dp-snd-xx node under dpsub node)
- no other device in the same power domain (dpdma node has no
"power-domains = <&zynqmp_firmware PD_DP>" property)

So there is a scenario as below:
1) DP device enters suspend state <- call zynqmp_gpd_power_off
2) zynqmp_disp_crtc_setup_clock <- configurate register VPLL_FRAC_CFG
3) pm_runtime_get_sync <- call zynqmp_gpd_power_on and clear previous
VPLL_FRAC_CFG configuration
4) clk_prepare_enable(disp->pclk) <- enable failed since VPLL_FRAC_CFG
configuration is corrupted

From above, we can see that pm_runtime_get_sync may clear register
VPLL_FRAC_CFG configuration and result the failure of clk enabling.
Putting pm_runtime_get_sync at the very beginning of the function
zynqmp_disp_crtc_atomic_enable can resolve this issue.

Signed-off-by: Quanyang Wang <quanyang.wang@windriver.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/xlnx/zynqmp_disp.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xlnx/zynqmp_disp.c b/drivers/gpu/drm/xlnx/zynqmp_disp.c
index 8cd8af35cfaa..205c72a249b7 100644
--- a/drivers/gpu/drm/xlnx/zynqmp_disp.c
+++ b/drivers/gpu/drm/xlnx/zynqmp_disp.c
@@ -1447,9 +1447,10 @@ zynqmp_disp_crtc_atomic_enable(struct drm_crtc *crtc,
struct drm_display_mode *adjusted_mode = &crtc->state->adjusted_mode;
int ret, vrefresh;

+ pm_runtime_get_sync(disp->dev);
+
zynqmp_disp_crtc_setup_clock(crtc, adjusted_mode);

- pm_runtime_get_sync(disp->dev);
ret = clk_prepare_enable(disp->pclk);
if (ret) {
dev_err(disp->dev, "failed to enable a pixel clock\n");
--
2.30.2