linux-kernel - Re: [RFC RESEND v1 pinctrl-next 0/1] add blink and activity functions to SGPIO

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Message-ID: <64ae73ce.050a0220.fe1a6.4b8a@mx.google.com>
Date:   Wed, 12 Jul 2023 03:59:10 +0200
From:   Christian Marangi <ansuelsmth@...il.com>
To:     Colin Foster <colin.foster@...advantage.com>
Cc:     linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        UNGLinuxDriver@...rochip.com,
        Daniel Machon <daniel.machon@...rochip.com>,
        Steen Hegelund <Steen.Hegelund@...rochip.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <florian.fainelli@...adcom.com>,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: Re: [RFC RESEND v1 pinctrl-next 0/1] add blink and activity
 functions to SGPIO

On Tue, Jul 11, 2023 at 07:22:49PM -0700, Colin Foster wrote:
> Preface (new for resend):
> 
> This is a resend of a patch I'd sent a couple years back. At that time,
> I was told to wait for hardware-offloaded LEDS. It looks like that time
> has finally come, so I've changed this from PATCH down to an RFC to make
> sure this is the right approach for the framework.
> 
> Ocelot chips (VSC7511, VSC7512, VSC7513, VSC7514) have support for
> hardware-offloaded LEDs based on network activity. This is currenty
> managed by way of pinctrl-microchip-sgpio (and this current patch).
> 
> The purpose of this resend is two-fold. First, to come up with an idea
> of how this pinctrl-microchip-sgpio module can fit in with the new
> hardware-offloaded netdev triggers Christian Marangi recently added. Is
> this something that should be in the pinctrl module itself? Or should
> there be a drivers/net/ethernet/mscc/ocelot_leds.c module that I should
> add?
>

I'm a bit out of the loop on what magic OEM did to make LED work on
ocelot but I feel an ocelot_leds submodule is needed.

To correctly supports the hw many API needs to be defined and for switch
I would stick with how things are done with qca8k, codewise and DT wise
(with how LEDs are defined in DT)

Ideally the feature for MAC will be generilized and added to the DSA ops
struct, so having things in the DSA driver would make the migration
easier.

> The second reason is maybe there's someone out there who might also be
> considering implementing this. This might be a good starting point if
> someone is eager to get coding. On my priority list, this is quite low
> so I'll get to it eventually, but maybe not even in this dev cycle.
> That's why I'm including the original patch.
> 
> 
> Any suggestions on how to approach this problem are welcome.
> 
> 
> 
> 
> (You can probably stop reading here)
> 
> 
> Original Header:
> 
> Expose a debugfs / devicetree interface for Microsemi SGPIO controllers.
> By writing values of 2-5, the SGPIO pins can be configured for either
> automatic blinking or activity.
> 
> The implementation is modeled after the code in
> /drivers/pinctrl/pinctrl-ocelot.c.
> 
> I have only tested this with currently out-of-tree patches for the
> VSC7512 that I hope to get in soon. They are not needed for VSC7513 /
> VSC7514, SPARX5, or LUTON - but I don't have any hardware to test.
> 
> Of note: the 7512 chip has a discrepancy between the datasheet and the
> registers. The datahseet claims 20Hz blink default frequency, the
> registers claim 5 Hz default frequency for BMODE_0. I override the
> OCELOT registers to correct for this. I don't know if that is needed for
> LUTON or SPARX, but having two blink modes at the same frequency isn't
> beneficial. As such, I make the blink modes match the 5Hz / 20Hz for the
> two modes.
> 
> Tested with VSC7512 by way of:
> echo SGPIO_O_p1b0 {blink0,blink1,activity0,activity1} > 
> /sys/kernel/debug/pinctrl/pinctrl-sgpio-pinctrl-sgpio-output/pinmux-select
> 
> LEDs blink!
> 
> 
> Colin Foster (1):
>   pinctrl: microchip-sgpio: add activity and blink functionality
> 
>  drivers/pinctrl/pinctrl-microchip-sgpio.c | 135 +++++++++++++++++++++-
>  1 file changed, 130 insertions(+), 5 deletions(-)
> 
> -- 
> 2.25.1
> 

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