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SubjectRe: [PATCH] drm: xlnx: call pm_runtime_get_sync before setting pixel clock
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Ping.

Any comment on this patch?

Thanks,

Quanyang

On 3/10/21 12:59 PM, quanyang.wang@windriver.com wrote:
> From: Quanyang Wang <quanyang.wang@windriver.com>
>
> 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>
> ---
> 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 148add0ca1d6..909e6c265406 100644
> --- a/drivers/gpu/drm/xlnx/zynqmp_disp.c
> +++ b/drivers/gpu/drm/xlnx/zynqmp_disp.c
> @@ -1445,9 +1445,10 @@ 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");

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