Hi Niklas,
On Friday, 27 April 2018 02:28:32 EEST Niklas Söderlund wrote:
> On 2018-04-27 00:30:25 +0300, Laurent Pinchart wrote:
> > On Thursday, 26 April 2018 23:21:21 EEST Niklas Söderlund wrote:
> >> A V4L2 driver for Renesas R-Car MIPI CSI-2 receiver. The driver
> >> supports the R-Car Gen3 SoCs where separate CSI-2 hardware blocks are
> >> connected between the video sources and the video grabbers (VIN).
> >>
> >> Driver is based on a prototype by Koji Matsuoka in the Renesas BSP.
> >>
> >> Signed-off-by: Niklas Söderlund <[email protected]>
> >> Reviewed-by: Hans Verkuil <[email protected]>
> >> Reviewed-by: Maxime Ripard <[email protected]>
> >> Reviewed-by: Laurent Pinchart <[email protected]>
> >>
> >> ---
> >>
> >> * Changes since v13
> >> - Change return rcar_csi2_formats + i to return &rcar_csi2_formats[i].
> >> - Add define for PHCLM_STOPSTATECKL.
> >> - Update spelling in comments.
> >> - Update calculation in rcar_csi2_calc_phypll() according to
> >> https://linuxtv.org/downloads/v4l-dvb-apis/kapi/csi2.html. The one
> >> before v14 did not take into account that 2 bits per sample is
> >> transmitted.
> >
> > Just one small comment about this, please see below.
> >
> >> - Use Geert's suggestion of (1 << priv->lanes) - 1 instead of switch
> >> statement to set correct number of lanes to enable.
> >> - Change hex constants in hsfreqrange_m3w_h3es1[] to lower case to match
> >> style of rest of file.
> >> - Switch to %u instead of 0x%x when printing bus type.
> >> - Switch to %u instead of %d for priv->lanes which is unsigned.
> >> - Add MEDIA_BUS_FMT_YUYV8_1X16 to the list of supported formats in
> >> rcar_csi2_formats[].
> >> - Fixed bps for MEDIA_BUS_FMT_YUYV10_2X10 to 20 and not 16.
> >> - Set INTSTATE after PL-11 is confirmed to match flow chart in
> >> datasheet.
> >> - Change priv->notifier.subdevs == NULL to !priv->notifier.subdevs.
> >> - Add Maxime's and laurent's tags.
> >> ---
> >>
> >> drivers/media/platform/rcar-vin/Kconfig | 12 +
> >> drivers/media/platform/rcar-vin/Makefile | 1 +
> >> drivers/media/platform/rcar-vin/rcar-csi2.c | 883 ++++++++++++++++++++
> >> 3 files changed, 896 insertions(+)
> >> create mode 100644 drivers/media/platform/rcar-vin/rcar-csi2.c
> >
> > [snip]
> >
> >> diff --git a/drivers/media/platform/rcar-vin/rcar-csi2.c
> >> b/drivers/media/platform/rcar-vin/rcar-csi2.c new file mode 100644
> >> index 0000000000000000..49b29d5680f9d80b
> >> --- /dev/null
> > > +++ b/drivers/media/platform/rcar-vin/rcar-csi2.c
> >
> > [snip]
> >
> >> +static int rcar_csi2_calc_phypll(struct rcar_csi2 *priv, unsigned int
> >> bpp,
> >> + u32 *phypll)
> >> +{
> >> + const struct phypll_hsfreqrange *hsfreq;
> >> + struct v4l2_subdev *source;
> >> + struct v4l2_ctrl *ctrl;
> >> + u64 mbps;
> >> +
> >> + if (!priv->remote)
> >> + return -ENODEV;
> >> +
> >> + source = priv->remote;
> >> +
> >> + /* Read the pixel rate control from remote */
> >> + ctrl = v4l2_ctrl_find(source->ctrl_handler, V4L2_CID_PIXEL_RATE);
> >> + if (!ctrl) {
> >> + dev_err(priv->dev, "no pixel rate control in subdev %s\n",
> >> + source->name);
> >> + return -EINVAL;
> >> + }
> >> +
> >> + /*
> >> + * Calculate the phypll in mbps (from v4l2 documentation)
> >> + * link_freq = (pixel_rate * bits_per_sample) / (2 * nr_of_lanes)
> >> + */
> >> + mbps = v4l2_ctrl_g_ctrl_int64(ctrl) * bpp;
> >> + do_div(mbps, priv->lanes * 2000000);
> >
> > pixel rate * bits per sample will give you the overall bit rate, which you
> > then divide by the number of lanes to get the bitrate per lane, and then
> > by 2 as D-PHY is a DDR PHY and transmits 2 bits per clock cycle. You then
> > end up with the link frequency, which is thus expressed in MHz, not in
> > Mbps. I would thus name the mbps variable freq, and rename the
> > phypll_hsfreqrange mbps field to freq (maybe with a small comment right
> > after the field to tell the value is expressed in MHz).
>
> I agree that freq would be a better name for what it represents. Never
> the less I prefer to stick with mbps as that is whats used in the
> datasheet. See Table '25.9 HSFREQRANGE Bit Set Values'.
>
> With this in mind if you still feel strongly about renaming it I could
> do so. But at lest for me it feels more useful to easily be able to map
> the variable to the datasheet tables :-)
After reading the datasheet I don't care too strongly about a rename, but I
now care about getting it right :-) The datasheet clearly specifies the
maximum data rate to be 1.5 Gbps / lane (section 25.1.1 Features), and figure
25.9 corroborates that and shows a corresponding frequency of 750 MHz. I thus
believe that the values in table 25.9 and 25.10 are indeed bitrates (in Mbps /
lane), so I think you shouldn't divide by 2 in the above formula.
> >> + for (hsfreq = priv->info->hsfreqrange; hsfreq->mbps != 0; hsfreq++)
> >> + if (hsfreq->mbps >= mbps)
> >> + break;
> >> +
> >> + if (!hsfreq->mbps) {
> >> + dev_err(priv->dev, "Unsupported PHY speed (%llu Mbps)", mbps);
> >> + return -ERANGE;
> >> + }
> >> +
> >> + dev_dbg(priv->dev, "PHY HSFREQRANGE requested %llu got %u Mbps\n",
> >> mbps,
> >> + hsfreq->mbps);
> >> +
> >> + *phypll = PHYPLL_HSFREQRANGE(hsfreq->reg);
> >> +
> >> + return 0;
> >> +}
> >
> > [snip]
--
Regards,
Laurent Pinchart
