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

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Date:   Wed, 23 Feb 2022 23:14:12 +0800
From:   Sui Jingfeng <15330273260@....cn>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Thomas Zimmermann <tzimmermann@...e.de>,
        Roland Scheidegger <sroland@...are.com>,
        Zack Rusin <zackr@...are.com>,
        Christian Gmeiner <christian.gmeiner@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Andrey Zhizhikin <andrey.zhizhikin@...ca-geosystems.com>,
        Sam Ravnborg <sam@...nborg.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Ilia Mirkin <imirkin@...m.mit.edu>,
        Qing Zhang <zhangqing@...ngson.cn>,
        suijingfeng <suijingfeng@...ngson.cn>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Randy Dunlap <rdunlap@...radead.org>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v10 3/4] drm/lsdc: add drm driver for loongson display
 controller


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;
     }

  ....

}