linux-kernel - Re: [PATCH v4 23/36] media: imx: Add MIPI CSI-2 Receiver subdev driver

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Message-ID: <c858831f-6ce3-54b7-ef03-857129edb0bf@gmail.com>
Date:   Fri, 17 Feb 2017 10:27:01 -0800
From:   Steve Longerbeam <slongerbeam@...il.com>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     robh+dt@...nel.org, mark.rutland@....com, shawnguo@...nel.org,
        kernel@...gutronix.de, fabio.estevam@....com,
        linux@...linux.org.uk, mchehab@...nel.org, hverkuil@...all.nl,
        nick@...anahar.org, markus.heiser@...marIT.de,
        laurent.pinchart+renesas@...asonboard.com, bparrot@...com,
        geert@...ux-m68k.org, arnd@...db.de, sudipm.mukherjee@...il.com,
        minghsiu.tsai@...iatek.com, tiffany.lin@...iatek.com,
        jean-christophe.trotin@...com, horms+renesas@...ge.net.au,
        niklas.soderlund+renesas@...natech.se, robert.jarzmik@...e.fr,
        songjun.wu@...rochip.com, andrew-ct.chen@...iatek.com,
        gregkh@...uxfoundation.org, shuah@...nel.org,
        sakari.ailus@...ux.intel.com, pavel@....cz,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
        devel@...verdev.osuosl.org,
        Steve Longerbeam <steve_longerbeam@...tor.com>
Subject: Re: [PATCH v4 23/36] media: imx: Add MIPI CSI-2 Receiver subdev
 driver



On 02/17/2017 06:16 AM, Philipp Zabel wrote:
> On Fri, 2017-02-17 at 11:47 +0100, Philipp Zabel wrote:
>> On Wed, 2017-02-15 at 18:19 -0800, Steve Longerbeam wrote:
>>> +static void csi2_dphy_init(struct csi2_dev *csi2)
>>> +{
>>> +	/*
>>> +	 * FIXME: 0x14 is derived from a fixed D-PHY reference
>>> +	 * clock from the HSI_TX PLL, and a fixed target lane max
>>> +	 * bandwidth of 300 Mbps. This value should be derived
>>
>> If the table in https://community.nxp.com/docs/DOC-94312 is correct,
>> this should be 850 Mbps. Where does this 300 Mbps value come from?
>
> I got it, the dptdin_map value for 300 Mbps is 0x14 in the Rockchip DSI
> driver. But that value is written to the register as HSFREQRANGE_SEL(x):
>
> #define HSFREQRANGE_SEL(val)    (((val) & 0x3f) << 1)

Ah you are right, 0x14 would be a "testdin" value of 0x0a, which from
the Rockchip table would be 950 MHz per lane.

But thanks for pointing the table at
https://community.nxp.com/docs/DOC-94312. That table is what
should be referenced in the above comment (850 MHz per lane
for a 27MHz reference clock). I will update the comment based
on that table.

Steve



>
> which is 0x28. Further, the Rockchip D-PHY probably is another version,
> as its max_mbps goes up to 1500.
>
>