linux-kernel - Re: Re: [PATCH RFC 02/21] media: cadence: csi2rx: configure DPHY before starting source stream

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Date: Fri, 23 Feb 2024 12:53:57 +0530
From: Jai Luthra <j-luthra@...com>
To: Julien Massot <julien.massot@...labora.com>
CC: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
        Mauro Carvalho Chehab
	<mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Hans
 Verkuil <hverkuil-cisco@...all.nl>,
        Vaishnav Achath <vaishnav.a@...com>,
        Maxime Ripard <mripard@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof
 Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley
	<conor+dt@...nel.org>, <linux-media@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        Vignesh
 Raghavendra <vigneshr@...com>,
        Aradhya Bhatia <a-bhatia1@...com>, Devarsh
 Thakkar <devarsht@...com>,
        Changhuang Liang
	<changhuang.liang@...rfivetech.com>,
        Jack Zhu <jack.zhu@...rfivetech.com>,
        Jayshri Pawar <jpawar@...ence.com>
Subject: Re: Re: [PATCH RFC 02/21] media: cadence: csi2rx: configure DPHY
 before starting source stream

Hi Julien,

On Feb 22, 2024 at 15:29:54 +0100, Julien Massot wrote:
> Hi Jai,
> 
> On 2/22/24 12:31, Jai Luthra wrote:
> > From: Pratyush Yadav <p.yadav@...com>
> > 
> > When the source device is operating above 1.5 Gbps per lane, it needs to
> > send the Skew Calibration Sequence before sending any HS data. If the
> > DPHY is initialized after the source stream is started, then it might
> > miss the sequence and not be able to receive data properly. Move the
> > start of source subdev to the end of the sequence to make sure
> > everything is ready to receive data before the source starts streaming.
> > 
> > Signed-off-by: Pratyush Yadav <p.yadav@...com>
> > Signed-off-by: Jai Luthra <j-luthra@...com>
> 
> Thanks for your patch!
> This patch is useful even at lower data rate than 1.5 Gbps.
> I'm having the issue at 800Mbps with max96714F deserializer.
> 
> Should this patch deserve a Fixes tag?

Thanks, yes in that case I will add the fixes tag and repost this fix 
separately so it can be picked sooner.

> Fixes: 3295cf1241d3 ("media: cadence: Add support for external dphy")
> 
> Reviewed-by: Julien Massot <julien.massot@...labora.com>
> Tested-by: Julien Massot <julien.massot@...labora.com>
> 
> > ---
> >   drivers/media/platform/cadence/cdns-csi2rx.c | 26 ++++++++++++++------------
> >   1 file changed, 14 insertions(+), 12 deletions(-)
> > 
> > diff --git a/drivers/media/platform/cadence/cdns-csi2rx.c b/drivers/media/platform/cadence/cdns-csi2rx.c
> > index 70b7f8a9e4f2..75e602c1d762 100644
> > --- a/drivers/media/platform/cadence/cdns-csi2rx.c
> > +++ b/drivers/media/platform/cadence/cdns-csi2rx.c
> > @@ -243,10 +243,6 @@ static int csi2rx_start(struct csi2rx_priv *csi2rx)
> >   	writel(reg, csi2rx->base + CSI2RX_STATIC_CFG_REG);
> > -	ret = v4l2_subdev_call(csi2rx->source_subdev, video, s_stream, true);
> > -	if (ret)
> > -		goto err_disable_pclk;
> > -
> >   	/* Enable DPHY clk and data lanes. */
> >   	if (csi2rx->dphy) {
> >   		reg = CSI2RX_DPHY_CL_EN | CSI2RX_DPHY_CL_RST;
> > @@ -256,6 +252,13 @@ static int csi2rx_start(struct csi2rx_priv *csi2rx)
> >   		}
> >   		writel(reg, csi2rx->base + CSI2RX_DPHY_LANE_CTRL_REG);
> > +
> > +		ret = csi2rx_configure_ext_dphy(csi2rx);
> > +		if (ret) {
> > +			dev_err(csi2rx->dev,
> > +				"Failed to configure external DPHY: %d\n", ret);
> > +			goto err_disable_pclk;
> > +		}
> >   	}
> >   	/*
> > @@ -295,14 +298,9 @@ static int csi2rx_start(struct csi2rx_priv *csi2rx)
> >   	reset_control_deassert(csi2rx->sys_rst);
> > -	if (csi2rx->dphy) {
> > -		ret = csi2rx_configure_ext_dphy(csi2rx);
> > -		if (ret) {
> > -			dev_err(csi2rx->dev,
> > -				"Failed to configure external DPHY: %d\n", ret);
> > -			goto err_disable_sysclk;
> > -		}
> > -	}
> > +	ret = v4l2_subdev_call(csi2rx->source_subdev, video, s_stream, true);
> > +	if (ret)
> > +		goto err_disable_sysclk;
> >   	clk_disable_unprepare(csi2rx->p_clk);
> > @@ -316,6 +314,10 @@ static int csi2rx_start(struct csi2rx_priv *csi2rx)
> >   		clk_disable_unprepare(csi2rx->pixel_clk[i - 1]);
> >   	}
> > +	if (csi2rx->dphy) {
> > +		writel(0, csi2rx->base + CSI2RX_DPHY_LANE_CTRL_REG);
> > +		phy_power_off(csi2rx->dphy);
> > +	}
> >   err_disable_pclk:
> >   	clk_disable_unprepare(csi2rx->p_clk);
> > 
> 
> -- 
> Julien Massot
> Senior Software Engineer
> Collabora Ltd.
> Platinum Building, St John's Innovation Park, Cambridge CB4 0DS, UK
> Registered in England & Wales, no. 5513718

-- 
Thanks,
Jai

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