[PATCH 5/9] drm/ast: dp501: Use struct drm_edid and helpers

[Jocelyn Falempe]

On 06/08/2024 14:52, Thomas Zimmermann wrote:
> Convert DP501 support to struct drm_edid and its helpers. Simplifies
> and modernizes the EDID handling.
> 
> The driver reads 4 bytes at once, but the overall read length is now
> variable. Therefore update the EDID read loop to never return more than
> the requested bytes.

Thanks for this patch.
I don't have a hardware to test, but I think it may break the EDID reading.

> 
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
> ---
>   drivers/gpu/drm/ast/ast_dp501.c | 92 ++++++++++++++++++++-------------
>   1 file changed, 55 insertions(+), 37 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ast/ast_dp501.c b/drivers/gpu/drm/ast/ast_dp501.c
> index 478efa226170..1c5a4902d4c2 100644
> --- a/drivers/gpu/drm/ast/ast_dp501.c
> +++ b/drivers/gpu/drm/ast/ast_dp501.c
> @@ -318,32 +318,63 @@ static bool ast_dp501_is_connected(struct ast_device *ast)
>   	return true;
>   }
>   
> -static bool ast_dp501_read_edid(struct drm_device *dev, u8 *ediddata)
> +static int ast_dp512_read_edid_block(void *data, u8 *buf, unsigned int block, size_t len)
>   {
> -	struct ast_device *ast = to_ast_device(dev);
> -	u32 i, boot_address, offset, data;
> -	u32 *pEDIDidx;
> +	struct ast_device *ast = data;
> +	u32 i, boot_address, offset, ediddata;
>   
> -	if (!ast_dp501_is_connected(ast))
> -		return false;
> +	if (block > (512 / EDID_LENGTH))
> +		return -EIO;
> +
> +	offset = AST_DP501_EDID_DATA + block * EDID_LENGTH;
>   
>   	if (ast->config_mode == ast_use_p2a) {
>   		boot_address = get_fw_base(ast);
>   
> -		/* Read EDID */
> -		offset = AST_DP501_EDID_DATA;
> -		for (i = 0; i < 128; i += 4) {
> -			data = ast_mindwm(ast, boot_address + offset + i);
> -			pEDIDidx = (u32 *)(ediddata + i);
> -			*pEDIDidx = data;
> +		for (i = 0; i < len; i += 4) {
> +			ediddata = ast_mindwm(ast, boot_address + offset + i);

I think "i" is always a multiple of 4, so the switch case is broken, and 
will always go to case 0, so reading only 1 byte every 4 bytes ?

> +
> +			switch (i % 4) {
> +			case 3:
> +				*buf = (ediddata >> 24) & 0xff;
> +				++buf;
> +				fallthrough;
> +			case 2:
> +				*buf = (ediddata >> 16) & 0xff;
> +				++buf;
> +				fallthrough;
> +			case 1:
> +				*buf = (ediddata >> 8) & 0xff;
> +				++buf;
> +				fallthrough;
> +			case 0:
> +				*buf = (ediddata) & 0xff;
> +				++buf;
> +				break;
> +			}
>   		}
>   	} else {
> -		/* Read EDID */
> -		offset = AST_DP501_EDID_DATA;
> -		for (i = 0; i < 128; i += 4) {
> -			data = readl(ast->dp501_fw_buf + offset + i);
> -			pEDIDidx = (u32 *)(ediddata + i);
> -			*pEDIDidx = data;
> +		for (i = 0; i < len; i += 4) {
> +			ediddata = readl(ast->dp501_fw_buf + offset + i);
> +
> +			switch (i % 4) {
> +			case 3:
> +				*buf = (ediddata >> 24) & 0xff;
> +				++buf;
> +				fallthrough;
> +			case 2:
> +				*buf = (ediddata >> 16) & 0xff;
> +				++buf;
> +				fallthrough;
> +			case 1:
> +				*buf = (ediddata >> 8) & 0xff;
> +				++buf;
> +				fallthrough;
> +			case 0:
> +				*buf = (ediddata) & 0xff;
> +				++buf;
> +				break;
> +			}
>   		}
>   	}
>   
> @@ -511,29 +542,16 @@ static const struct drm_encoder_helper_funcs ast_dp501_encoder_helper_funcs = {
>   
>   static int ast_dp501_connector_helper_get_modes(struct drm_connector *connector)
>   {
> -	void *edid;
> -	bool succ;
> +	struct ast_device *ast = to_ast_device(connector->dev);
> +	const struct drm_edid *drm_edid;
>   	int count;
>   
> -	edid = kmalloc(EDID_LENGTH, GFP_KERNEL);
> -	if (!edid)
> -		goto err_drm_connector_update_edid_property;
> -
> -	succ = ast_dp501_read_edid(connector->dev, edid);
> -	if (!succ)
> -		goto err_kfree;
> -
> -	drm_connector_update_edid_property(connector, edid);
> -	count = drm_add_edid_modes(connector, edid);
> -	kfree(edid);
> +	drm_edid = drm_edid_read_custom(connector, ast_dp512_read_edid_block, ast);
> +	drm_edid_connector_update(connector, drm_edid);
> +	count = drm_edid_connector_add_modes(connector);
> +	drm_edid_free(drm_edid);
>   
>   	return count;
> -
> -err_kfree:
> -	kfree(edid);
> -err_drm_connector_update_edid_property:
> -	drm_connector_update_edid_property(connector, NULL);
> -	return 0;
>   }
>   
>   static int ast_dp501_connector_helper_detect_ctx(struct drm_connector *connector,