linux-kernel - Re: [PATCH] ARM: dts: NSP: Use hardware I2C for BCM958625HR

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Message-ID: <667acf12-cff3-8955-8849-b99db50375bb@broadcom.com>
Date:   Fri, 13 Dec 2019 14:11:26 -0800
From:   Ray Jui <ray.jui@...adcom.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        "maintainer:BROADCOM IPROC ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: dts: NSP: Use hardware I2C for BCM958625HR



On 2019-12-13 11:51 a.m., Florian Fainelli wrote:
> Now that the i2c-bcm-iproc driver has been fixed to permit reading more
> than 63 bytes in a single transaction with commit fd01eecdf959 ("i2c:
> iproc: Fix i2c master read more than 63 bytes") we no longer need to
> bitbang i2c over GPIOs which was necessary before to allow the
> PHYLINK/SFP subsystems to read SFP modules.
> 

This is good to hear!

> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>   arch/arm/boot/dts/bcm958625hr.dts | 15 +++++----------
>   1 file changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm/boot/dts/bcm958625hr.dts b/arch/arm/boot/dts/bcm958625hr.dts
> index a2c9de35ddfb..536fb24f38bb 100644
> --- a/arch/arm/boot/dts/bcm958625hr.dts
> +++ b/arch/arm/boot/dts/bcm958625hr.dts
> @@ -55,18 +55,9 @@
>   		priority = <200>;
>   	};
>   
> -	/* Hardware I2C block cannot do more than 63 bytes per transfer,
> -	 * which would prevent reading from a SFP's EEPROM (256 byte).
> -	 */
> -	i2c1: i2c {
> -		compatible = "i2c-gpio";
> -		sda-gpios = <&gpioa 5 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN)>;
> -		scl-gpios = <&gpioa 4 (GPIO_ACTIVE_HIGH | GPIO_OPEN_DRAIN)>;
> -	};
> -

So I suppose GPIO 4 and 5 from the 'gpioa' controller are tied to the 
same SCL/SDA pins from i2c0 and they are internally muxed, right?

Is the mux to GPIO done automatically when pins are configured as GPIO, 
and therefore you don't require any additional changes to pinmux to make 
this work, after changing it back to use real I2C0 block below?

>   	sfp: sfp {
>   		compatible = "sff,sfp";
> -		i2c-bus = <&i2c1>;
> +		i2c-bus = <&i2c0>;
>   		mod-def0-gpios = <&gpioa 28 GPIO_ACTIVE_LOW>;
>   		los-gpios = <&gpioa 24 GPIO_ACTIVE_HIGH>;
>   		tx-fault-gpios = <&gpioa 30 GPIO_ACTIVE_HIGH>;
> @@ -74,6 +65,10 @@
>   	};
>   };
>   
> +&i2c0 {
> +	status = "okay";
> +};
> +
>   &amac0 {
>   	status = "okay";
>   };
> 

Change looks good to me.

Reviewed-by: Ray Jui <ray.jui@...adcom.com>

Thanks,

Ray