From mboxrd@z Thu Jan 1 00:00:00 1970 From: josh.wu@atmel.com (Josh Wu) Date: Fri, 19 Dec 2014 14:11:52 +0800 Subject: [PATCH v4 2/5] media: ov2640: add async probe function In-Reply-To: References: <1418869646-17071-1-git-send-email-josh.wu@atmel.com> <1418869646-17071-3-git-send-email-josh.wu@atmel.com> Message-ID: <5493C1A8.4050204@atmel.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi, Guennadi Thanks for the review. On 12/19/2014 5:59 AM, Guennadi Liakhovetski wrote: > Hi Josh, > > Thanks for your patches! > > On Thu, 18 Dec 2014, Josh Wu wrote: > >> To support async probe for ov2640, we need remove the code to get 'mclk' >> in ov2640_probe() function. oterwise, if soc_camera host is not probed >> in the moment, then we will fail to get 'mclk' and quit the ov2640_probe() >> function. >> >> So in this patch, we move such 'mclk' getting code to ov2640_s_power() >> function. That make ov2640 survive, as we can pass a NULL (priv-clk) to >> soc_camera_set_power() function. >> >> And if soc_camera host is probed, the when ov2640_s_power() is called, >> then we can get the 'mclk' and that make us enable/disable soc_camera >> host's clock as well. >> >> Signed-off-by: Josh Wu >> --- >> v3 -> v4: >> v2 -> v3: >> v1 -> v2: >> no changes. >> >> drivers/media/i2c/soc_camera/ov2640.c | 31 +++++++++++++++++++++---------- >> 1 file changed, 21 insertions(+), 10 deletions(-) >> >> diff --git a/drivers/media/i2c/soc_camera/ov2640.c b/drivers/media/i2c/soc_camera/ov2640.c >> index 1fdce2f..9ee910d 100644 >> --- a/drivers/media/i2c/soc_camera/ov2640.c >> +++ b/drivers/media/i2c/soc_camera/ov2640.c >> @@ -739,6 +739,15 @@ static int ov2640_s_power(struct v4l2_subdev *sd, int on) >> struct i2c_client *client = v4l2_get_subdevdata(sd); >> struct soc_camera_subdev_desc *ssdd = soc_camera_i2c_to_desc(client); >> struct ov2640_priv *priv = to_ov2640(client); >> + struct v4l2_clk *clk; >> + >> + if (!priv->clk) { >> + clk = v4l2_clk_get(&client->dev, "mclk"); >> + if (IS_ERR(clk)) >> + dev_warn(&client->dev, "Cannot get the mclk. maybe soc-camera host is not probed yet.\n"); >> + else >> + priv->clk = clk; >> + } >> >> return soc_camera_set_power(&client->dev, ssdd, priv->clk, on); >> } >> @@ -1078,21 +1087,21 @@ static int ov2640_probe(struct i2c_client *client, >> if (priv->hdl.error) >> return priv->hdl.error; >> >> - priv->clk = v4l2_clk_get(&client->dev, "mclk"); >> - if (IS_ERR(priv->clk)) { >> - ret = PTR_ERR(priv->clk); >> - goto eclkget; >> - } >> - >> ret = ov2640_video_probe(client); > The first thing the above ov2640_video_probe() function will do is call > ov2640_s_power(), which will request the clock. So, by moving requesting > the clock from ov2640_probe() to ov2640_s_power() doesn't change how > probing will be performed, am I right? yes, you are right. In this patch, the "mclk" will requested by ov2640_s_power(). The reason why I put the getting "mclk" code from ov2640_probe() to ov2640_s_power() is : as the "mclk" here is camera host's peripheral clock. That means ov2640 still can be probed properly (read ov2640 id) even no "mclk". So when I move this code to ov2640_s_power(), otherwise the ov2640_probe() will be failed or DEFER_PROBE. Is this true for all camera host? If it's not true, then I think use -EPROBE_DEFER would be a proper way. > Or are there any other patched, > that change that, that I'm overseeing? > > If I'm right, then I would propose an approach, already used in other > drivers instead of this one: return -EPROBE_DEFER if the clock isn't > available during probing. See ef6672ea35b5bb64ab42e18c1a1ffc717c31588a for > an example. Or did I misunderstand anything? Actually months ago I already done a version of ov2640 patch which use -EPROBE_DEFER way. But now I think the ov2640 can be probed correctly without "mclk", so it is no need to return -EPROBE_DEFER. And the v4l2 asyn API can handle the synchronization of host. So I prefer to use this way. What do you think about this? Best Regards, Josh Wu > > Thanks > Guennadi > >> if (ret) { >> - v4l2_clk_put(priv->clk); >> -eclkget: >> - v4l2_ctrl_handler_free(&priv->hdl); >> + goto evideoprobe; >> } else { >> dev_info(&adapter->dev, "OV2640 Probed\n"); >> } >> >> + ret = v4l2_async_register_subdev(&priv->subdev); >> + if (ret < 0) >> + goto evideoprobe; >> + >> + return 0; >> + >> +evideoprobe: >> + v4l2_ctrl_handler_free(&priv->hdl); >> return ret; >> } >> >> @@ -1100,7 +1109,9 @@ static int ov2640_remove(struct i2c_client *client) >> { >> struct ov2640_priv *priv = to_ov2640(client); >> >> - v4l2_clk_put(priv->clk); >> + v4l2_async_unregister_subdev(&priv->subdev); >> + if (priv->clk) >> + v4l2_clk_put(priv->clk); >> v4l2_device_unregister_subdev(&priv->subdev); >> v4l2_ctrl_handler_free(&priv->hdl); >> return 0; >> -- >> 1.9.1 >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-media" in > the body of a message to majordomo at vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html