Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
HMM_SOURCE_IP: 10.64.8.31:44458.435332613
HMM_ATTACHE_NUM: 0000
HMM_SOURCE_TYPE: SMTP
Received: from clientip-114.242.206.180 (unknown [10.64.8.31])
        by 189.cn (HERMES) with SMTP id 30AE11001F7;
        Wed, 23 Feb 2022 23:14:17 +0800 (CST)
Received: from  ([114.242.206.180])
        by gateway-151646-dep-b7fbf7d79-bwdqx with ESMTP id 90e95b07aa22426594cd3a88c70e7830 for maxime@cerno.tech;
        Wed, 23 Feb 2022 23:14:21 CST
X-Transaction-ID: 90e95b07aa22426594cd3a88c70e7830
X-Real-From: 15330273260@189.cn
X-Receive-IP: 114.242.206.180
X-MEDUSA-Status: 0
Sender: 15330273260@189.cn
Message-ID: <0d4a75c4-78bb-4aed-0fa8-88e9cc165896@189.cn>
Date:   Wed, 23 Feb 2022 23:14:12 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.5.0
Subject: Re: [PATCH v10 3/4] drm/lsdc: add drm driver for loongson display
 controller
Content-Language: en-US
To:     Maxime Ripard <maxime@cerno.tech>
Cc:     Thomas Zimmermann <tzimmermann@suse.de>,
        Roland Scheidegger <sroland@vmware.com>,
        Zack Rusin <zackr@vmware.com>,
        Christian Gmeiner <christian.gmeiner@gmail.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Rob Herring <robh+dt@kernel.org>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Andrey Zhizhikin <andrey.zhizhikin@leica-geosystems.com>,
        Sam Ravnborg <sam@ravnborg.org>,
        "David S . Miller" <davem@davemloft.net>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        Lucas Stach <l.stach@pengutronix.de>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Ilia Mirkin <imirkin@alum.mit.edu>,
        Qing Zhang <zhangqing@loongson.cn>,
        suijingfeng <suijingfeng@loongson.cn>,
        linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org, dri-devel@lists.freedesktop.org,
        Randy Dunlap <rdunlap@infradead.org>,
        kernel test robot <lkp@intel.com>
References: <20220220145554.117854-1-15330273260@189.cn>
 <20220220145554.117854-4-15330273260@189.cn>
 <20220222082747.66otrkc4zwvhem7w@houat>
 <54ea69d7-2fac-74dc-2ef6-843a666cff85@189.cn>
 <20220223143912.m727fie3vtdkvklo@houat>
From:   Sui Jingfeng <15330273260@189.cn>
In-Reply-To: <20220223143912.m727fie3vtdkvklo@houat>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
X-Spam-Status: No, score=-1.6 required=5.0 tests=BAYES_00,
	FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,FROM_LOCAL_DIGITS,
	FROM_LOCAL_HEX,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,
	NICE_REPLY_A,RDNS_NONE,SPF_HELO_NONE,SPOOFED_FREEMAIL_NO_RDNS,
	T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
	lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


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;
     }

  ....

}