linux-kernel - Re: [PATCH v3] drm/ast: Fix modeset failed on DisplayPort

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Date:   Thu, 1 Jun 2023 11:04:40 +0200
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Jammy Huang <jammy_huang@...eedtech.com>, airlied@...hat.com,
        airlied@...il.com, daniel@...ll.ch
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v3] drm/ast: Fix modeset failed on DisplayPort

Hi

Am 01.06.23 um 02:48 schrieb Jammy Huang:
> If we switch display and update cursor together, it could lead to
> modeset failed because of concurrent access to IO registers.
> 
> Add lock protection in DP's edid access to avoid this problem.

Merged into drm-misc-fixes. Thanks for the patch.

Best regards
Thomas

> 
> Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>
> Signed-off-by: Jammy Huang <jammy_huang@...eedtech.com>
> ---
>   v3 changes:
>    - Update label name after mutex added.
>   v2 changes:
>    - Fix build error since new struct ast_device is used.
> ---
>   drivers/gpu/drm/ast/ast_mode.c | 15 +++++++++++++--
>   1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
> index 36374828f6c8..b3c670af6ef2 100644
> --- a/drivers/gpu/drm/ast/ast_mode.c
> +++ b/drivers/gpu/drm/ast/ast_mode.c
> @@ -1647,6 +1647,8 @@ static int ast_dp501_output_init(struct ast_device *ast)
>   static int ast_astdp_connector_helper_get_modes(struct drm_connector *connector)
>   {
>   	void *edid;
> +	struct drm_device *dev = connector->dev;
> +	struct ast_device *ast = to_ast_device(dev);
>   
>   	int succ;
>   	int count;
> @@ -1655,9 +1657,17 @@ static int ast_astdp_connector_helper_get_modes(struct drm_connector *connector)
>   	if (!edid)
>   		goto err_drm_connector_update_edid_property;
>   
> +	/*
> +	 * Protect access to I/O registers from concurrent modesetting
> +	 * by acquiring the I/O-register lock.
> +	 */
> +	mutex_lock(&ast->ioregs_lock);
> +
>   	succ = ast_astdp_read_edid(connector->dev, edid);
>   	if (succ < 0)
> -		goto err_kfree;
> +		goto err_mutex_unlock;
> +
> +	mutex_unlock(&ast->ioregs_lock);
>   
>   	drm_connector_update_edid_property(connector, edid);
>   	count = drm_add_edid_modes(connector, edid);
> @@ -1665,7 +1675,8 @@ static int ast_astdp_connector_helper_get_modes(struct drm_connector *connector)
>   
>   	return count;
>   
> -err_kfree:
> +err_mutex_unlock:
> +	mutex_unlock(&ast->ioregs_lock);
>   	kfree(edid);
>   err_drm_connector_update_edid_property:
>   	drm_connector_update_edid_property(connector, NULL);
> 
> base-commit: e338142b39cf40155054f95daa28d210d2ee1b2d

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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