[PATCH u-boot v2019.04-aspeed-openbmc] pinctrl: ast2400: add support for TXD3/RXD3 pins

[Ryan Chen]

Hello,
> -----Original Message-----
> From: Zev Weiss <zev at bewilderbeest.net>
> Sent: Tuesday, December 14, 2021 11:21 AM
> To: Ryan Chen <ryan_chen at aspeedtech.com>
> Cc: openbmc at lists.ozlabs.org; Joel Stanley <joel at jms.id.au>; ChiaWei Wang
> <chiawei_wang at aspeedtech.com>
> Subject: Re: [PATCH u-boot v2019.04-aspeed-openbmc] pinctrl: ast2400: add
> support for TXD3/RXD3 pins
> 
> On Mon, Dec 13, 2021 at 05:39:17PM PST, Ryan Chen wrote:
> >Hello,
> >
> >> -----Original Message-----
> >> From: Zev Weiss <zev at bewilderbeest.net>
> >> Sent: Tuesday, December 14, 2021 9:33 AM
> >> To: Ryan Chen <ryan_chen at aspeedtech.com>
> >> Cc: openbmc at lists.ozlabs.org; Joel Stanley <joel at jms.id.au>; ChiaWei
> >> Wang <chiawei_wang at aspeedtech.com>
> >> Subject: Re: [PATCH u-boot v2019.04-aspeed-openbmc] pinctrl: ast2400:
> >> add support for TXD3/RXD3 pins
> >>
> >> On Mon, Dec 13, 2021 at 05:22:52PM PST, Ryan Chen wrote:
> >> >Hello,
> >> >	You may need claim for function group for link, not for pin link.
> >> >	Ex.
> >> >	static struct aspeed_sig_desc uart3_link[] = {
> >> >		{ 0x80, BIT(22), 0},
> >> >		{ 0x80, BIT(23), 0},
> >> >	}
> >> >
> >> >	ast2400_groups[] = {
> >> >	{ "UART3", 2, uart3_link },
> >> >Ryan
> >>
> >> Hi Ryan,
> >>
> >> That possibility occurred to me, but the existing function/group
> >> names in arch/arm/dts/ast2400.dtsi (lines 1130-1133 and 1375-1378)
> >> made me think they should be separate.
> >This device tree is copied from Linux kernel.
> >
> >> I'm certainly not an expert on pinctrl stuff though...is there some
> >> other existing logic or mechanism to link a "UART3" to the separate
> >> "TXD3" and "RXD3" in the device tree?
> >There is no separate in u-boot device tree.
> 
> Perhaps we're misunderstanding each other...
> 
> https://github.com/openbmc/u-boot/blob/a570745a1a836e351bd4b1131f23a4
> fa5013d6dd/arch/arm/dts/ast2400.dtsi#L1130-L1133
> 
> and
> 
> https://github.com/openbmc/u-boot/blob/a570745a1a836e351bd4b1131f23a4
> fa5013d6dd/arch/arm/dts/ast2400.dtsi#L1375-L1378
> 
The following is my point.
https://github.com/openbmc/u-boot/blob/a570745a1a836e351bd4b1131f23a4fa5013d6dd/arch/arm/dts/ast2400.dtsi#L3

> look fairly separate to me?
> 
> >May I know why you need separate?
> 
> In my particular case I don't need these two to be separate, but it seems
> conceivable that there might be other cases that would require a different set
> of signals to be enabled for a generic "UART3" group -- possibly more
> (sideband signals like CTS and such), or perhaps even fewer (e.g. if you had an
> output-only UART3 just for logging or something, and only needed TXD3 for
> that, but still wanted to use pin
> B14 as GPIOE7 instead of RXD3).  Keeping them separate seems like it leaves
> things as flexible as possible, avoiding imposing any artificial constraints.
> 
> 
> Zev