linux-kernel - Re: [PATCH v2 2/3] drivers/tty/serial/8250: add DT property for aspeed vuart sirq polarity

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Message-ID: <YGVXuyqOyxc8kcQz@hatter.bewilderbeest.net>
Date:   Thu, 1 Apr 2021 00:18:51 -0500
From:   Zev Weiss <zev@...ilderbeest.net>
To:     Joel Stanley <joel@....id.au>
Cc:     Jeremy Kerr <jk@...abs.org>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-aspeed <linux-aspeed@...ts.ozlabs.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Jeffery <andrew@...id.au>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>, linux-serial@...r.kernel.org
Subject: Re: [PATCH v2 2/3] drivers/tty/serial/8250: add DT property for
 aspeed vuart sirq polarity

On Wed, Mar 31, 2021 at 11:15:44PM CDT, Joel Stanley wrote:
>On Thu, 1 Apr 2021 at 00:57, Zev Weiss <zev@...ilderbeest.net> wrote:
>>
>> This provides a simple boolean to use instead of the deprecated
>> aspeed,sirq-polarity-sense property.
>>
>> Signed-off-by: Zev Weiss <zev@...ilderbeest.net>
>> ---
>>  drivers/tty/serial/8250/8250_aspeed_vuart.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/tty/serial/8250/8250_aspeed_vuart.c b/drivers/tty/serial/8250/8250_aspeed_vuart.c
>> index c33e02cbde93..e5ef9f957f9a 100644
>> --- a/drivers/tty/serial/8250/8250_aspeed_vuart.c
>> +++ b/drivers/tty/serial/8250/8250_aspeed_vuart.c
>> @@ -482,6 +482,9 @@ static int aspeed_vuart_probe(struct platform_device *pdev)
>>                 of_node_put(sirq_polarity_sense_args.np);
>>         }
>>
>> +       if (of_property_read_bool(np, "aspeed,sirq-active-high"))
>> +               aspeed_vuart_set_sirq_polarity(vuart, 1);
>
>This assumes the default is always low, so we don't need a property to
>set it to that state?
>
>Would it make more sense to have the property describe if it's high or
>low? (I'm happy for the answer to be "no", as we've gotten by for the
>past few years without it).
>

Yeah, that sounds like better way to approach it -- I think I'll 
rearrange as Andrew suggested in 
https://lore.kernel.org/openbmc/d66753ee-7db2-41e5-9fe5-762b1ab678bc@www.fastmail.com/

>This brings up another point. We already have the sysfs file for
>setting the lpc address, from userspace. In OpenBMC land this can be
>set with obmc-console-client (/etc/obmc-console.conf). Should we add
>support to that application for setting the irq polarity too, and do
>away with device tree descriptions?
>

I guess I might lean slightly toward keeping the DT description so that 
if for whatever reason obmc-console-server flakes out and doesn't start 
you're better positioned to try banging on /dev/ttyS* manually if you're 
desperate.  Though I suppose that in turn might imply that I'm arguing 
for adding DT properties for lpc_address and sirq too, and if you're 
really that desperate you can just fiddle with sysfs anyway, so...shrug?  
I could be convinced either way fairly easily.


Zev