[PATCH v10 3/4] drm/lsdc: add drm driver for loongson display controller

[Sui Jingfeng]

On 2022/2/23 22:39, Maxime Ripard wrote:
> On Tue, Feb 22, 2022 at 10:46:35PM +0800, Sui Jingfeng wrote:
>> On 2022/2/22 16:27, Maxime Ripard wrote:
>>>> +	if (!of_device_is_available(output)) {
>>>> +		of_node_put(output);
>>>> +		drm_info(ddev, "connector%d is not available\n", index);
>>>> +		return NULL;
>>>> +	}
>>>> +
>>>> +	disp_tims_np = of_get_child_by_name(output, "display-timings");
>>>> +	if (disp_tims_np) {
>>>> +		lsdc_get_display_timings_from_dtb(output, &lconn->disp_tim);
>>>> +		lconn->has_disp_tim = true;
>>>> +		of_node_put(disp_tims_np);
>>>> +		drm_info(ddev, "Found display timings provided by connector%d\n", index);
>>>> +	}
>>>> +
>>>> +	connector_type = lsdc_get_connector_type(ddev, output, index);
>>>> +
>>>> +	if (output) {
>>>> +		of_node_put(output);
>>>> +		output = NULL;
>>>> +	}
>>>> +
>>>> +DT_SKIPED:
>>>> +
>>>> +	/* Only create the i2c channel if display timing is not provided */
>>>> +	if (!lconn->has_disp_tim) {
>>>> +		const struct lsdc_chip_desc * const desc = ldev->desc;
>>>> +
>>>> +		if (desc->have_builtin_i2c)
>>>> +			lconn->ddc = lsdc_create_i2c_chan(ddev, index);
>>>> +		else
>>>> +			lconn->ddc = lsdc_get_i2c_adapter(ddev, index);
>>> This looks weird: the connector bindings have a property to store the
>>> i2c controller connected to the DDC lines, so you should use that
>>> instead.
>>>
>> This is not  weird,  ast, mgag200, hibmc do the same thing.
> And none of them have DT support.
>
> Maxime

You are wrong, ast driver have dt support. See ast_detect_config_mode() 
in drm/ast/ast_main.c

static void ast_detect_config_mode(struct drm_device *dev, u32 *scu_rev)
{
     struct device_node *np = dev->dev->of_node;
     struct ast_private *ast = to_ast_private(dev);
     struct pci_dev *pdev = to_pci_dev(dev->dev);
     uint32_t data, jregd0, jregd1;

     /* Defaults */
     ast->config_mode = ast_use_defaults;
     *scu_rev = 0xffffffff;

     /* Check if we have device-tree properties */
     if (np && !of_property_read_u32(np, "aspeed,scu-revision-id",
                     scu_rev)) {
         /* We do, disable P2A access */
         ast->config_mode = ast_use_dt;
         drm_info(dev, "Using device-tree for configuration\n");
         return;
     }

  ....

}