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

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Date:   Wed, 29 Dec 2021 10:30:54 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Colin Foster <colin.foster@...advantage.com>
Cc:     linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Linus Walleij <linus.walleij@...aro.org>,
        UNGLinuxDriver@...rochip.com,
        Steen Hegelund <Steen.Hegelund@...rochip.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>
Subject: Re: [PATCH v1 pinctrl-next 0/1] add blink and activity functions to
 SGPIO

On Tue, Dec 28, 2021 at 04:37:28PM -0800, Colin Foster wrote:
> 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

Hi Colin

Since this is an LED, you should be using the Linux LED interface in
/sys/class/leds. See Documentation/leds/leds-class.rst. It includes a
way to make an LED blink, using hardware.

Activity is another story. I assume you mean Ethernet frame Rx and Tx?
For that you should wait until the Ethernet LED offload code
eventually lands.

	   Andrew