linux-kernel - Re: [PATCH 05/14] media: sun6i-csi: Only configure the interface data width for parallel

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Message-ID: <20201027093119.GD168350@aptenodytes>
Date:   Tue, 27 Oct 2020 10:31:19 +0100
From:   Paul Kocialkowski <paul.kocialkowski@...tlin.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devel@...verdev.osuosl.org, linux-sunxi@...glegroups.com,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        Yong Deng <yong.deng@...ewell.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Vinod Koul <vkoul@...nel.org>,
        Helen Koike <helen.koike@...labora.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Hans Verkuil <hverkuil@...all.nl>, kevin.lhopital@...mail.com,
        Kévin L'hôpital <kevin.lhopital@...tlin.com>
Subject: Re: [PATCH 05/14] media: sun6i-csi: Only configure the interface
 data width for parallel

Hi,

On Mon 26 Oct 20, 17:00, Maxime Ripard wrote:
> On Fri, Oct 23, 2020 at 07:45:37PM +0200, Paul Kocialkowski wrote:
> > Bits related to the interface data width do not have any effect when
> > the CSI controller is taking input from the MIPI CSI-2 controller.
> 
> I guess it would be clearer to mention that the data width is only
> applicable for parallel here.

Understood, will change the wording in the next version.

> > In prevision of adding support for this case, set these bits
> > conditionally so there is no ambiguity.
> > 
> > Co-developed-by: Kévin L'hôpital <kevin.lhopital@...tlin.com>
> > Signed-off-by: Kévin L'hôpital <kevin.lhopital@...tlin.com>
> > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>
> > ---
> >  .../platform/sunxi/sun6i-csi/sun6i_csi.c      | 42 +++++++++++--------
> >  1 file changed, 25 insertions(+), 17 deletions(-)
> > 
> > diff --git a/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.c b/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.c
> > index 5d2389a5cd17..a876a05ea3c7 100644
> > --- a/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.c
> > +++ b/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi.c
> > @@ -378,8 +378,13 @@ static void sun6i_csi_setup_bus(struct sun6i_csi_dev *sdev)
> >  	unsigned char bus_width;
> >  	u32 flags;
> >  	u32 cfg;
> > +	bool input_parallel = false;
> >  	bool input_interlaced = false;
> >  
> > +	if (endpoint->bus_type == V4L2_MBUS_PARALLEL ||
> > +	    endpoint->bus_type == V4L2_MBUS_BT656)
> > +		input_parallel = true;
> > +
> >  	if (csi->config.field == V4L2_FIELD_INTERLACED
> >  	    || csi->config.field == V4L2_FIELD_INTERLACED_TB
> >  	    || csi->config.field == V4L2_FIELD_INTERLACED_BT)
> > @@ -395,6 +400,26 @@ static void sun6i_csi_setup_bus(struct sun6i_csi_dev *sdev)
> >  		 CSI_IF_CFG_HREF_POL_MASK | CSI_IF_CFG_FIELD_MASK |
> >  		 CSI_IF_CFG_SRC_TYPE_MASK);
> >  
> > +	if (input_parallel) {
> > +		switch (bus_width) {
> > +		case 8:
> > +			cfg |= CSI_IF_CFG_IF_DATA_WIDTH_8BIT;
> > +			break;
> > +		case 10:
> > +			cfg |= CSI_IF_CFG_IF_DATA_WIDTH_10BIT;
> > +			break;
> > +		case 12:
> > +			cfg |= CSI_IF_CFG_IF_DATA_WIDTH_12BIT;
> > +			break;
> > +		case 16: /* No need to configure DATA_WIDTH for 16bit */
> > +			break;
> > +		default:
> > +			dev_warn(sdev->dev, "Unsupported bus width: %u\n",
> > +				 bus_width);
> > +			break;
> > +		}
> > +	}
> > +
> >  	if (input_interlaced)
> >  		cfg |= CSI_IF_CFG_SRC_TYPE_INTERLACED;
> >  	else
> > @@ -440,23 +465,6 @@ static void sun6i_csi_setup_bus(struct sun6i_csi_dev *sdev)
> >  		break;
> >  	}
> >  
> > -	switch (bus_width) {
> > -	case 8:
> > -		cfg |= CSI_IF_CFG_IF_DATA_WIDTH_8BIT;
> > -		break;
> > -	case 10:
> > -		cfg |= CSI_IF_CFG_IF_DATA_WIDTH_10BIT;
> > -		break;
> > -	case 12:
> > -		cfg |= CSI_IF_CFG_IF_DATA_WIDTH_12BIT;
> > -		break;
> > -	case 16: /* No need to configure DATA_WIDTH for 16bit */
> > -		break;
> > -	default:
> > -		dev_warn(sdev->dev, "Unsupported bus width: %u\n", bus_width);
> > -		break;
> > -	}
> > -
> 
> Is there any reason to move it around?

The main reason is cosmetics: input_parallel is introduced to match the already
existing input_interlaced variable, so it made sense to me to have both of these
conditionals one after the other instead of spreading them randomly.

I can mention this in the commit log if you prefer.

-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

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