linux-kernel - Re: [PATCH 01/10] net: stmmac: Enable stmmac main clock when probing hardware

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Date:	Mon, 9 Dec 2013 15:26:09 +0800
From:	Chen-Yu Tsai <wens@...e.org>
To:	Giuseppe CAVALLARO <peppe.cavallaro@...com>
Cc:	netdev <netdev@...r.kernel.org>,
	Rob Herring <rob.herring@...xeda.com>,
	devicetree <devicetree@...r.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-sunxi <linux-sunxi@...glegroups.com>,
	Srinivas Kandagatla <srinivas.kandagatla@...com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>
Subject: Re: [PATCH 01/10] net: stmmac: Enable stmmac main clock when probing hardware

Hi Peppe,

On Mon, Dec 9, 2013 at 3:14 PM, Giuseppe CAVALLARO
<peppe.cavallaro@...com> wrote:
> Hello Chen-Yu
>
>
> On 12/6/2013 6:29 PM, Chen-Yu Tsai wrote:
>>
>> Signed-off-by: Chen-Yu Tsai <wens@...e.org>
>> ---
>>
>> Guiseppe previously stated that the "stmmaceth" clock is the
>> main clock that drives the IP. The stmmac driver does not
>> enable this clock during the probe phase. When the driver is
>> built in to the kernel, this is fine because the clock maybe
>> on by default, or the boot loader had enabled it.
>>
>> If stmmac is built as a module, when the module is loaded,
>> the clock may be found unused and disabled by the kernel.
>
>
> the clk_prepare_enable is then called in the open.
> Is it not working for you?
> Do you mean that the stmmac_hw_init fails if you do not move
> the clk_get and clk_prepare_enable on top of the stmmac_dvr_probe?
>

Exactly. The clock needs to be enabled prior to stmmac_dvr_probe.
Otherwise, stmmac_mdio_register will fail to find a usable PHY.

The DWMAC core I am working with does not support chip ID or
HW capability flags. I suspect those would fail, too.

Disabling the clock at the end of stmmac_dvr_probe is to make
sure it plays nice with existing power management callbacks.

Chen-Yu

>>
>>   drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 24
>> +++++++++++++----------
>>   1 file changed, 14 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> index 8d4ccd3..7da71ed 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> @@ -2688,10 +2688,17 @@ struct stmmac_priv *stmmac_dvr_probe(struct device
>> *device,
>>         if ((phyaddr >= 0) && (phyaddr <= 31))
>>                 priv->plat->phy_addr = phyaddr;
>>
>> +       priv->stmmac_clk = clk_get(priv->device, STMMAC_RESOURCE_NAME);
>> +       if (IS_ERR(priv->stmmac_clk)) {
>> +               pr_warn("%s: warning: cannot get CSR clock\n", __func__);
>> +               goto error_clk_get;
>> +       }
>> +       clk_prepare_enable(priv->stmmac_clk);
>> +
>>         /* Init MAC and get the capabilities */
>>         ret = stmmac_hw_init(priv);
>>         if (ret)
>> -               goto error_free_netdev;
>> +               goto error_hw_init;
>>
>>         ndev->netdev_ops = &stmmac_netdev_ops;
>>
>> @@ -2729,12 +2736,6 @@ struct stmmac_priv *stmmac_dvr_probe(struct device
>> *device,
>>                 goto error_netdev_register;
>>         }
>>
>> -       priv->stmmac_clk = clk_get(priv->device, STMMAC_RESOURCE_NAME);
>> -       if (IS_ERR(priv->stmmac_clk)) {
>> -               pr_warn("%s: warning: cannot get CSR clock\n", __func__);
>> -               goto error_clk_get;
>> -       }
>> -
>>         /* If a specific clk_csr value is passed from the platform
>>          * this means that the CSR Clock Range selection cannot be
>>          * changed at run-time and it is fixed. Viceversa the driver'll
>> try to
>> @@ -2759,15 +2760,18 @@ struct stmmac_priv *stmmac_dvr_probe(struct device
>> *device,
>>                 }
>>         }
>>
>> +       clk_disable_unprepare(priv->stmmac_clk);
>> +
>>         return priv;
>>
>>   error_mdio_register:
>> -       clk_put(priv->stmmac_clk);
>> -error_clk_get:
>>         unregister_netdev(ndev);
>>   error_netdev_register:
>>         netif_napi_del(&priv->napi);
>> -error_free_netdev:
>> +error_hw_init:
>> +       clk_disable_unprepare(priv->stmmac_clk);
>> +       clk_put(priv->stmmac_clk);
>> +error_clk_get:
>>         free_netdev(ndev);
>>
>>         return NULL;
>>
>
--
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