linux-kernel - Re: [PATCH 2/4] net: hix5hd2_gmac: add reset control and clock signals

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Date:	Fri, 12 Aug 2016 13:48:24 -0500
From:	Rob Herring <robh@...nel.org>
To:	Dongpo Li <lidongpo@...ilicon.com>
Cc:	mark.rutland@....com, mturquette@...libre.com,
	sboyd@...eaurora.org, linux@...linux.org.uk,
	zhangfei.gao@...aro.org, yisen.zhuang@...wei.com,
	salil.mehta@...wei.com, davem@...emloft.net, arnd@...db.de,
	andrew@...n.ch, xuejiancheng@...ilicon.com,
	benjamin.chenhao@...ilicon.com, howell.yang@...ilicon.com,
	netdev@...r.kernel.org, devicetree@...r.kernel.org,
	linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] net: hix5hd2_gmac: add reset control and clock
 signals

On Thu, Aug 11, 2016 at 05:01:53PM +0800, Dongpo Li wrote:
> From: Li Dongpo <lidongpo@...ilicon.com>
> 
> Add three reset control signals, "mac_core_rst", "mac_ifc_rst" and
> "phy_rst".
> The following diagram explained how the reset signals work.
> 
>                         SoC
> |-----------------------------------------------------
> |                               ------                |
> |                               | cpu |               |
> |                               ------                |
> |                                  |                  |
> |                              ------------ AMBA bus  |
> |                         GMAC     |                  |
> |                            ----------------------   |
> | ------------- mac_core_rst | --------------      |  |
> | |clock and   |-------------->|   mac core  |     |  |
> | |reset       |             | --------------      |  |
> | |generator   |----         |       |             |  |
> | -------------     |        | ----------------    |  |
> |          |        ---------->| mac interface |   |  |
> |          |     mac_ifc_rst | ----------------    |  |
> |          |                 |       |             |  |
> |          |                 | ------------------  |  |
> |          |phy_rst          | | RGMII interface | |  |
> |          |                 | ------------------  |  |
> |          |                 ----------------------   |
> |----------|------------------------------------------|
>            |                          |
>            |                      ----------
>            |--------------------- |PHY chip |
>                                   ----------
> 
> The "mac_core_rst" represents "mac core reset signal", it resets
> the mac core including packet processing unit, descriptor processing unit,
> tx engine, rx engine, control unit.
> The "mac_ifc_rst" represents "mac interface reset signal", it resets
> the mac interface. The mac interface unit connects mac core and
> data interface like MII/RMII/RGMII. After we set a new value of
> interface mode, we must reset mac interface to reload the new mode value.
> The "phy_rst" represents "phy reset signal", it does a hardware reset
> on the PHY chip. This reset signal is optinal if the PHY can work well
> without the hardware reset.
> 
> Add one more clock signal, the existing is MAC core clock,
> and the new one is MAC interface clock.
> 
> Signed-off-by: Dongpo Li <lidongpo@...ilicon.com>
> ---
>  .../bindings/net/hisilicon-hix5hd2-gmac.txt        |  16 ++-
>  drivers/net/ethernet/hisilicon/hix5hd2_gmac.c      | 140 +++++++++++++++++++--
>  2 files changed, 143 insertions(+), 13 deletions(-)


> 
> @@ -807,16 +829,26 @@ static int hix5hd2_net_open(struct net_device *dev)
>  	struct phy_device *phy;
>  	int ret;
>  
> -	ret = clk_prepare_enable(priv->clk);
> +	ret = clk_prepare_enable(priv->mac_core_clk);
> +	if (ret < 0) {
> +		netdev_err(dev, "failed to enable mac core clk %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = clk_prepare_enable(priv->mac_ifc_clk);
>  	if (ret < 0) {
> -		netdev_err(dev, "failed to enable clk %d\n", ret);
> +		clk_disable_unprepare(priv->mac_core_clk);
> +		netdev_err(dev, "failed to enable mac ifc clk %d\n", ret);

This change will break with existing DTs. The mac_ifc_clk should be 
optional.

Rob

>  		return ret;
>  	}