linux-kernel - Re: [PATCH] drm/msm/dsi: Use single function for reset

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Date:   Wed, 15 Jun 2022 15:30:11 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Luca Weiss <luca@...tu.xyz>, dri-devel@...ts.freedesktop.org
Cc:     ~postmarketos/upstreaming@...ts.sr.ht, phone-devel@...r.kernel.org,
        Vladimir Lypak <vladimir.lypak@...il.com>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Vinod Koul <vkoul@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Jonathan Marek <jonathan@...ek.ca>,
        linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm/dsi: Use single function for reset

On 11/06/2022 01:02, Luca Weiss wrote:
> From: Vladimir Lypak <vladimir.lypak@...il.com>
> 
> There is currently two function for performing reset: dsi_sw_reset and
> dsi_sw_reset_restore. Only difference betwean those is that latter one
> assumes that DSI controller is enabled. In contrary former one assumes
> that controller is disabled and executed during power-on. However this
> assumtion is not true mobile devices which have boot splash set up by
> boot-loader.
> 
> This patch removes dsi_sw_reset_restore and makes dsi_sw_reset disable
> DSI controller during reset sequence if it's enabled.
> 
> Signed-off-by: Vladimir Lypak <vladimir.lypak@...il.com>
> Signed-off-by: Luca Weiss <luca@...tu.xyz>

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

> ---
>   drivers/gpu/drm/msm/dsi/dsi_host.c | 48 +++++++++++++-----------------
>   1 file changed, 21 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> index a95d5df52653..bab2634ebd11 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> @@ -1080,12 +1080,32 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
>   
>   static void dsi_sw_reset(struct msm_dsi_host *msm_host)
>   {
> +	u32 ctrl;
> +
> +	ctrl = dsi_read(msm_host, REG_DSI_CTRL);
> +
> +	if (ctrl & DSI_CTRL_ENABLE) {
> +		dsi_write(msm_host, REG_DSI_CTRL, ctrl & ~DSI_CTRL_ENABLE);
> +		/*
> +		 * dsi controller need to be disabled before
> +		 * clocks turned on
> +		 */
> +		wmb();
> +	}
> +
>   	dsi_write(msm_host, REG_DSI_CLK_CTRL, DSI_CLK_CTRL_ENABLE_CLKS);
>   	wmb(); /* clocks need to be enabled before reset */
>   
> +	/* dsi controller can only be reset while clocks are running */
>   	dsi_write(msm_host, REG_DSI_RESET, 1);
>   	msleep(DSI_RESET_TOGGLE_DELAY_MS); /* make sure reset happen */
>   	dsi_write(msm_host, REG_DSI_RESET, 0);
> +	wmb(); /* controller out of reset */
> +
> +	if (ctrl & DSI_CTRL_ENABLE) {
> +		dsi_write(msm_host, REG_DSI_CTRL, ctrl);
> +		wmb();	/* make sure dsi controller enabled again */
> +	}
>   }
>   
>   static void dsi_op_mode_config(struct msm_dsi_host *msm_host,
> @@ -1478,32 +1498,6 @@ static int dsi_cmds2buf_tx(struct msm_dsi_host *msm_host,
>   	return len;
>   }
>   
> -static void dsi_sw_reset_restore(struct msm_dsi_host *msm_host)
> -{
> -	u32 data0, data1;
> -
> -	data0 = dsi_read(msm_host, REG_DSI_CTRL);
> -	data1 = data0;
> -	data1 &= ~DSI_CTRL_ENABLE;
> -	dsi_write(msm_host, REG_DSI_CTRL, data1);
> -	/*
> -	 * dsi controller need to be disabled before
> -	 * clocks turned on
> -	 */
> -	wmb();
> -
> -	dsi_write(msm_host, REG_DSI_CLK_CTRL, DSI_CLK_CTRL_ENABLE_CLKS);
> -	wmb();	/* make sure clocks enabled */
> -
> -	/* dsi controller can only be reset while clocks are running */
> -	dsi_write(msm_host, REG_DSI_RESET, 1);
> -	msleep(DSI_RESET_TOGGLE_DELAY_MS); /* make sure reset happen */
> -	dsi_write(msm_host, REG_DSI_RESET, 0);
> -	wmb();	/* controller out of reset */
> -	dsi_write(msm_host, REG_DSI_CTRL, data0);
> -	wmb();	/* make sure dsi controller enabled again */
> -}
> -
>   static void dsi_hpd_worker(struct work_struct *work)
>   {
>   	struct msm_dsi_host *msm_host =
> @@ -1520,7 +1514,7 @@ static void dsi_err_worker(struct work_struct *work)
>   
>   	pr_err_ratelimited("%s: status=%x\n", __func__, status);
>   	if (status & DSI_ERR_STATE_MDP_FIFO_UNDERFLOW)
> -		dsi_sw_reset_restore(msm_host);
> +		dsi_sw_reset(msm_host);
>   
>   	/* It is safe to clear here because error irq is disabled. */
>   	msm_host->err_work_state = 0;


-- 
With best wishes
Dmitry