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Message-Id: <c79e93c3-1678-412f-87c5-2b757d806574@www.fastmail.com>
Date: Mon, 08 Nov 2021 10:51:48 +1030
From: "Andrew Jeffery" <andrew@...id.au>
To: "Chin-Ting Kuo" <chin-ting_kuo@...eedtech.com>,
"Rob Herring" <robh+dt@...nel.org>,
"Joel Stanley" <joel@....id.au>,
"Ulf Hansson" <ulf.hansson@...aro.org>
Cc: BMC-SW <BMC-SW@...eedtech.com>,
"Steven Lee" <steven_lee@...eedtech.com>,
"Michael Turquette" <mturquette@...libre.com>,
"Stephen Boyd" <sboyd@...nel.org>,
"Adrian Hunter" <adrian.hunter@...el.com>,
"linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
"openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>,
linux-mmc <linux-mmc@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>
Subject: Re: [PATCH 04/10] mmc: Add invert flag for clock phase signedness
On Sat, 6 Nov 2021, at 20:32, Chin-Ting Kuo wrote:
> Hi Andrew,
>>> > - rc = device_property_read_u32_array(dev, prop, degrees, 2);
>> > + rc = device_property_read_u32_array(dev, prop, degrees, 4);
>> > phase->valid = !rc;
>> > if (phase->valid) {
>> > - phase->in_deg = degrees[0];
>> > - phase->out_deg = degrees[1];
>> > + phase->inv_in_deg = degrees[0] ? true : false;
>> > + phase->in_deg = degrees[1];
>> > + phase->inv_out_deg = degrees[2] ? true : false;
>> > + phase->out_deg = degrees[3];
>>
>> This fundamentally breaks any in-tree users. We can't do this.
>>
>> In terms of the binding, if negative phase values are something we must do,
>> we can just extend the value range to include [-359, -1] right?
>
> Yes, agree it and I tried it before. But, it seems that the device tree
> doesn't support
> negative value with "-" prefixed and there is no device tree related
> API used to get
> the negative value from .dts. Thus, I tried to add an additional flag
> to present
> negative value.
>
Hmm. Still, I don't think we can break the binding this way.
Rob, Ulf, Adrian: What are your thoughts on handling phase offsets in
[-360, 360] in the binding? Do we append the flag field? Add a separate
property? I don't think interleaving the flags is desirable, though
interested in your thoughts.
Andrew
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