linux-kernel - Re: [PATCH] drm/bridge/synopsys: dsi: Wait for all active lanes to reach stop

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Date:   Thu, 25 Apr 2019 12:18:10 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Matt Redfearn <matt.redfearn@...nci.com>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Philippe Cornu <philippe.cornu@...com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Matthew Redfearn <matthew.redfearn@...nci.com>,
        Nickey Yang <nickey.yang@...k-chips.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Archit Taneja <architt@...eaurora.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH] drm/bridge/synopsys: dsi: Wait for all active lanes to
 reach stop

Hi Matt,

Thank you for the patch.

On Wed, Apr 24, 2019 at 02:21:40PM +0000, Matt Redfearn wrote:
> The Synopsys manual states that software should wait for all active
> lanes to reach stop state (User manual section 3.1.5). Currently the
> driver only waits for / checks that the clock lane is in stop state. Fix
> this by waiting for the mask of PHY STATUS bits corresponding to the
> active lanes to be set.
> 
> Signed-off-by: Matt Redfearn <matt.redfearn@...nci.com>

I don't have access to the datasheet, but the change makes sense.

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> ---
> 
>  drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> index bd15c21a177..38e88071363 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> @@ -189,6 +189,10 @@
>  #define DSI_PHY_TX_TRIGGERS		0xac
>  
>  #define DSI_PHY_STATUS			0xb0
> +#define PHY_STOP_STATE_LANE_3		BIT(11)
> +#define PHY_STOP_STATE_LANE_2		BIT(9)
> +#define PHY_STOP_STATE_LANE_1		BIT(7)
> +#define PHY_STOP_STATE_LANE_0		BIT(4)
>  #define PHY_STOP_STATE_CLK_LANE		BIT(2)
>  #define PHY_LOCK			BIT(0)
>  
> @@ -752,7 +756,7 @@ static void dw_mipi_dsi_dphy_init(struct dw_mipi_dsi *dsi)
>  
>  static void dw_mipi_dsi_dphy_enable(struct dw_mipi_dsi *dsi)
>  {
> -	u32 val;
> +	u32 val, mask;
>  	int ret;
>  
>  	dsi_write(dsi, DSI_PHY_RSTZ, PHY_ENFORCEPLL | PHY_ENABLECLK |
> @@ -763,11 +767,16 @@ static void dw_mipi_dsi_dphy_enable(struct dw_mipi_dsi *dsi)
>  	if (ret)
>  		DRM_DEBUG_DRIVER("failed to wait phy lock state\n");
>  
> +	mask = PHY_STOP_STATE_CLK_LANE | PHY_STOP_STATE_LANE_0;
> +	mask |= (dsi->lanes >= 2) ? PHY_STOP_STATE_LANE_1 : 0;
> +	mask |= (dsi->lanes >= 3) ? PHY_STOP_STATE_LANE_2 : 0;
> +	mask |= (dsi->lanes == 4) ? PHY_STOP_STATE_LANE_3 : 0;
> +
>  	ret = readl_poll_timeout(dsi->base + DSI_PHY_STATUS,
> -				 val, val & PHY_STOP_STATE_CLK_LANE, 1000,
> +				 val, (val & mask) == mask, 1000,
>  				 PHY_STATUS_TIMEOUT_US);
>  	if (ret)
> -		DRM_DEBUG_DRIVER("failed to wait phy clk lane stop state\n");
> +		DRM_DEBUG_DRIVER("failed to wait phy stop state\n");
>  }
>  
>  static void dw_mipi_dsi_clear_err(struct dw_mipi_dsi *dsi)

-- 
Regards,

Laurent Pinchart