Hi Hugues, On Tue, Jul 02, 2019 at 04:05:46PM +0000, Hugues FRUCHET wrote: > Hi Sakari, > > On 6/27/19 6:05 PM, Sakari Ailus wrote: > > Hi Hugues, > > > > On Thu, Jun 27, 2019 at 02:57:04PM +0200, Hugues Fruchet wrote: > >> Add support of V4L2_CID_LINK_FREQ, this is needed > >> by some CSI-2 receivers. > >> > >> 384MHz is exposed for the time being, corresponding > >> to 96MHz pixel clock with 2 bytes per pixel on 2 data lanes. > >> > >> This setup has been tested successfully with ST MIPID02 > >> CSI-2 to parallel bridge. > >> > >> Signed-off-by: Hugues Fruchet <hugues.fruchet@xxxxxx> > >> --- > > > > Thanks for the patch. > > > > The driver calculates the sensor configuration based on its configuration, > > and this needs to be reflected in the link frequency: it's not a static > > value. See e.g. ov5640_calc_sys_clk(). > > > > I know this code, but for a reason I don't understand yet, this seems > to not have effects on the CSI-2 link frequency. > > This has been verified with MIPID02 CSI-2 bridge which only work with > this fixed link frequency as input to program its ui_x4 register > setting, see > https://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg2028171.html. > All resolutions and all framerate have been tested succesfully with this > setting. > > Initially I tried to set the link frequency according to the value > computed in ov5640_calc_sys_clk() but it was only functional when > resolutions/framerate was close to the 384MHz value... > > As OV5640 D3 engineering board has been initially developped for > dragonboard, I'll dig into this and found this commit: > https://lore.kernel.org/patchwork/patch/886794/ > which set a fixed pixel rate value to 96MHz, which match perfectly > with the 384MHz value I found for link frequency... > > Perhaps other CSI-2 OV5640 users can comment about it and have the > explanations of what I experiment... > Maxime, Jacopo, do you have any idea about it ? I would also like to wee a comment from someone who's familiar with the device. Yet I can tell a static value of 348 MHz is clearly incorrect as it ignores sensor runtime configuration as well as platform configuration (external clock frequency for instance). Generally speaking, configuring a CSI-2 receiver to expect a particular frequency usually doesn't mean it's going to fail even if the transmitter uses a different frequency, albeit the likelihood of it not working increases as the difference grows. Could the problem be at the receiver's end? Have you checked what kind of values ov5640_calc_pclk() returns for different configurations? It would seem like that this is what the LINK_FREQ (divided by lanes and multiplied by two) should be. > > > >> version 2: > >> - do not set control read only as per Hans' comment: > >> See https://www.mail-archive.com/linux-media@xxxxxxxxxxxxxxx/msg147910.html > >> > >> drivers/media/i2c/ov5640.c | 10 ++++++++++ > >> 1 file changed, 10 insertions(+) > >> > >> diff --git a/drivers/media/i2c/ov5640.c b/drivers/media/i2c/ov5640.c > >> index 82d4ce9..e6307f3 100644 > >> --- a/drivers/media/i2c/ov5640.c > >> +++ b/drivers/media/i2c/ov5640.c > >> @@ -218,6 +218,7 @@ struct ov5640_ctrls { > >> struct v4l2_ctrl *test_pattern; > >> struct v4l2_ctrl *hflip; > >> struct v4l2_ctrl *vflip; > >> + struct v4l2_ctrl *link_freq; > >> }; > >> > >> struct ov5640_dev { > >> @@ -2198,6 +2199,10 @@ static int ov5640_try_fmt_internal(struct v4l2_subdev *sd, > >> return 0; > >> } > >> > >> +static const s64 link_freq_menu_items[] = { > >> + 384000000, > >> +}; > >> + > >> static int ov5640_set_fmt(struct v4l2_subdev *sd, > >> struct v4l2_subdev_pad_config *cfg, > >> struct v4l2_subdev_format *format) > >> @@ -2636,6 +2641,8 @@ static int ov5640_s_ctrl(struct v4l2_ctrl *ctrl) > >> case V4L2_CID_VFLIP: > >> ret = ov5640_set_ctrl_vflip(sensor, ctrl->val); > >> break; > >> + case V4L2_CID_LINK_FREQ: > >> + return 0; > >> default: > >> ret = -EINVAL; > >> break; > >> @@ -2703,6 +2710,9 @@ static int ov5640_init_controls(struct ov5640_dev *sensor) > >> V4L2_CID_POWER_LINE_FREQUENCY_AUTO, 0, > >> V4L2_CID_POWER_LINE_FREQUENCY_50HZ); > >> > >> + ctrls->link_freq = v4l2_ctrl_new_int_menu(hdl, ops, V4L2_CID_LINK_FREQ, > >> + 0, 0, link_freq_menu_items); > >> + > >> if (hdl->error) { > >> ret = hdl->error; > >> goto free_ctrls; > >> -- > >> 2.7.4 > >> > > > > BR, > Hugues. -- Sakari Ailus sakari.ailus@xxxxxxxxxxxxxxx
