From: Martin Kepplinger <martin.kepplinger@puri.sm>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: festevam@gmail.com, krzk@kernel.org, devicetree@vger.kernel.org,
kernel@pengutronix.de, kernel@puri.sm,
linux-arm-kernel@lists.infradead.org, linux-imx@nxp.com,
linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
linux-staging@lists.linux.dev, m.felsch@pengutronix.de,
mchehab@kernel.org, phone-devel@vger.kernel.org, robh@kernel.org,
shawnguo@kernel.org, slongerbeam@gmail.com
Subject: Re: [PATCH v6 2/3] media: imx: add a driver for i.MX8MQ mipi csi rx phy and controller
Date: Fri, 16 Jul 2021 10:47:14 +0200 [thread overview]
Message-ID: <e88d99abbdcbd6a1b2c27849f08721e79f237adc.camel@puri.sm> (raw)
In-Reply-To: <YPCuFA+utjudv11H@pendragon.ideasonboard.com>
Am Freitag, dem 16.07.2021 um 00:52 +0300 schrieb Laurent Pinchart:
> Hi Martin,
>
> On Thu, Jul 15, 2021 at 09:37:24AM +0200, Martin Kepplinger wrote:
> > Am Mittwoch, dem 14.07.2021 um 21:24 +0300 schrieb Laurent
> > Pinchart:
> > > On Wed, Jul 14, 2021 at 01:19:30PM +0200, Martin Kepplinger
> > > wrote:
> > > > Add a driver to support the i.MX8MQ MIPI CSI receiver. The
> > > > hardware side
> > > > is based on
> > > > https://source.codeaurora.org/external/imx/linux-imx/tree/drivers/media/platform/imx8/mxc-mipi-csi2_yav.c?h=imx_5.4.70_2.3.0
> > > >
> > > > It's built as part of VIDEO_IMX7_CSI because that's documented
> > > > to support
> > > > i.MX8M platforms. This driver adds i.MX8MQ support where
> > > > currently only the
> > > > i.MX8MM platform has been supported.
> > > >
> > > > Signed-off-by: Martin Kepplinger <martin.kepplinger@puri.sm>
> > > > ---
> > > > drivers/staging/media/imx/Makefile | 1 +
> > > > drivers/staging/media/imx/imx8mq-mipi-csi2.c | 949
> > > > +++++++++++++++++++
> > > > 2 files changed, 950 insertions(+)
> > > > create mode 100644 drivers/staging/media/imx/imx8mq-mipi-
> > > > csi2.c
> > > >
> > > > diff --git a/drivers/staging/media/imx/Makefile
> > > > b/drivers/staging/media/imx/Makefile
> > > > index 6ac33275cc97..19c2fc54d424 100644
> > > > --- a/drivers/staging/media/imx/Makefile
> > > > +++ b/drivers/staging/media/imx/Makefile
> > > > @@ -16,3 +16,4 @@ obj-$(CONFIG_VIDEO_IMX_CSI) += imx6-mipi-
> > > > csi2.o
>
> [snip]
>
> > > > +static int imx8mq_mipi_csi_calc_hs_settle(struct csi_state
> > > > *state)
> > > > +{
> > > > + u32 width = state-
> > > > >format_mbus[MIPI_CSI2_PAD_SINK].width;
> > > > + u32 height = state-
> > > > >format_mbus[MIPI_CSI2_PAD_SINK].height;
> > > > + s64 link_freq;
> > > > + u32 lane_rate;
> > > > +
> > > > + /* Calculate the line rate from the pixel rate. */
> > > > + link_freq = v4l2_get_link_freq(state->src_sd-
> > > > >ctrl_handler,
> > > > + state->csi2_fmt->width,
> > > > + state-
> > > > >bus.num_data_lanes * 2);
> > > > + if (link_freq < 0) {
> > > > + dev_err(state->dev, "Unable to obtain link
> > > > frequency: %d\n",
> > > > + (int)link_freq);
> > > > + return link_freq;
> > > > + }
> > > > +
> > > > + lane_rate = link_freq * 2;
> > > > + if (lane_rate < 80000000 || lane_rate > 1500000000) {
> > > > + dev_dbg(state->dev, "Out-of-bound lane rate
> > > > %u\n", lane_rate);
> > > > + return -EINVAL;
> > > > + }
> > > > +
> > > > + /*
> > > > https://community.nxp.com/t5/i-MX-Processors/Explenation-for-HS-SETTLE-parameter-in-MIPI-CSI-D-PHY-registers/m-p/764275/highlight/true#M118744
> > > > */
> > > > + if (lane_rate < 250000000)
> > > > + state->hs_settle = 0xb;
> > > > + else if (lane_rate < 500000000)
> > > > + state->hs_settle = 0x8;
> > > > + else
> > > > + state->hs_settle = 0x6;
> > >
> > > We could possibly compute this value based on the formula from
> > > the table
> > > in that page, but maybe that's overkill ? If you want to give it
> > > a try,
> > > it would be along those lines.
> > >
> > > /*
> > > * The D-PHY specification requires Ths-settle to be in
> > > the range
> > > * 85ns + 6*UI to 140ns + 10*UI, with the unit interval
> > > UI being half
> > > * the clock period.
> > > *
> > > * The Ths-settle value is expressed in the hardware as a
> > > multiple of
> > > * the Esc clock period:
> > > *
> > > * Ths-settle = (PRG_RXHS_SETTLE + 1) * Tperiod of
> > > RxClkInEsc
> > > *
> > > * Due to the one cycle inaccuracy introduced by
> > > rounding, the
> > > * documentation recommends picking a value away from the
> > > boundaries.
> > > * Let's pick the average.
> > > */
> > > esc_clk_rate = clk_get_rate(...);
> > >
> > > min_ths_settle = 85 + 6 * 1000000 / (lane_rate / 1000);
> > > max_ths_settle = 140 + 10 * 1000000 / (lane_rate / 1000);
> > > ths_settle = (min_ths_settle + max_ths_settle) / 2;
> > >
> > > state->hs_settle = ths_settle * esc_clk_rate / 1000000000
> > > - 1;
> >
> > I experimented a bit but would like to leave this as a task for
> > later
> > if that's ok. it's correct and simple now. also, using clks[i].clk
> > based on the name string would feel better to submit seperately
> > later.
>
> That's OK with me, but I may then submit a patch on top fairly soon
> :-)
> Have you been able to test if this code works on your device ? The
> main
> reason why I think it's better is that it doesn't hardcode a specific
> escape clock frequency assumption, so it should be able to
> accommodate a
> wider range of use cases. If we change it later, there's always a
> risk
> of regressions, while if we do this from the start, we'll figure out
> quickly if it doesn't work in some cases.
>
taking your code basically as-is doesn't yet work, but it helps a bit.
tbh I don't even know how to correctly read that table / calculation:
what is the exact relation of the calculated Ths_settle time inverval
to the hs_settle register bits?
if the 2 of us can't quickly figure it out I can ask NXP via that
community forum issue and I created
https://source.puri.sm/Librem5/linux-next/-/issues/340 so I won't
forget about it.
thanks!
next prev parent reply other threads:[~2021-07-16 8:47 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-14 11:19 [PATCH v6 0/3] media: imx: add support for imx8mq MIPI RX Martin Kepplinger
2021-07-14 11:19 ` [PATCH v6 1/3] dt-bindings: media: document the nxp,imx8mq-mipi-csi2 receiver phy and controller Martin Kepplinger
2021-07-14 15:44 ` Rob Herring
2021-07-14 17:53 ` Laurent Pinchart
2021-07-14 18:07 ` Martin Kepplinger
2021-07-14 11:19 ` [PATCH v6 2/3] media: imx: add a driver for i.MX8MQ mipi csi rx " Martin Kepplinger
2021-07-14 18:24 ` Laurent Pinchart
2021-07-15 6:49 ` Martin Kepplinger
2021-07-15 21:47 ` Laurent Pinchart
2021-07-15 7:37 ` Martin Kepplinger
2021-07-15 21:52 ` Laurent Pinchart
2021-07-16 8:47 ` Martin Kepplinger [this message]
2021-07-16 10:47 ` Laurent Pinchart
2021-07-19 10:46 ` Martin Kepplinger
2021-07-19 14:20 ` Martin Kepplinger
2021-07-14 11:19 ` [PATCH v6 3/3] arm64: dts: imx8mq: add mipi csi phy and csi bridge descriptions Martin Kepplinger
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