linux-kernel - Re: [PATCH 4/5] drm/msm/dsi: get the clocks into OFF state at init

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Date:   Mon, 1 Jul 2019 12:37:44 -0600
From:   Jeffrey Hugo <jhugo@...eaurora.org>
To:     Rob Clark <robdclark@...il.com>, dri-devel@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org
Cc:     freedreno@...ts.freedesktop.org, aarch64-laptops@...ts.linaro.org,
        linux-clk@...r.kernel.org, linux-pm@...r.kernel.org,
        Rob Clark <robdclark@...omium.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        Abhinav Kumar <abhinavk@...eaurora.org>,
        Sibi Sankar <sibis@...eaurora.org>,
        Mamta Shukla <mamtashukla555@...il.com>,
        Chandan Uddaraju <chandanu@...eaurora.org>,
        Archit Taneja <architt@...eaurora.org>,
        Rajesh Yadav <ryadav@...eaurora.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] drm/msm/dsi: get the clocks into OFF state at init

On 6/30/2019 9:01 AM, Rob Clark wrote:
> From: Rob Clark <robdclark@...omium.org>
> 
> Do an extra enable/disable cycle at init, to get the clks into disabled
> state in case bootloader left them enabled.
> 
> In case they were already enabled, the clk_prepare_enable() has no real
> effect, other than getting the enable_count/prepare_count into the right
> state so that we can disable clocks in the correct order.  This way we
> avoid having stuck clocks when we later want to do a modeset and set the
> clock rates.
> 
> Signed-off-by: Rob Clark <robdclark@...omium.org>
> ---
>   drivers/gpu/drm/msm/dsi/dsi_host.c         | 18 +++++++++++++++---
>   drivers/gpu/drm/msm/dsi/pll/dsi_pll_10nm.c |  1 +
>   2 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dsi/pll/dsi_pll_10nm.c b/drivers/gpu/drm/msm/dsi/pll/dsi_pll_10nm.c
> index aabab6311043..d0172d8db882 100644
> --- a/drivers/gpu/drm/msm/dsi/pll/dsi_pll_10nm.c
> +++ b/drivers/gpu/drm/msm/dsi/pll/dsi_pll_10nm.c
> @@ -354,6 +354,7 @@ static int dsi_pll_10nm_lock_status(struct dsi_pll_10nm *pll)
>   	if (rc)
>   		pr_err("DSI PLL(%d) lock failed, status=0x%08x\n",
>   		       pll->id, status);
> +rc = 0; // HACK, this will fail if PLL already running..

Umm, why?  Is this intentional?


-- 
Jeffrey Hugo
Qualcomm Datacenter Technologies as an affiliate of Qualcomm 
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.