Re: [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;
    }

 ....

}