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SubjectRe: [PATCH 01/10] net: stmmac: Enable stmmac main clock when probing hardware
Hi,

On Sat, Dec 7, 2013 at 6:33 PM, Maxime Ripard
<maxime.ripard@free-electrons.com> wrote:
> Hi,
>
> On Sat, Dec 07, 2013 at 01:29:34AM +0800, Chen-Yu Tsai wrote:
>> Signed-off-by: Chen-Yu Tsai <wens@csie.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.
>
> This should be your commit log.
>
> And this is actually not related to the fact that we are building it
> as a module or not. You'd face the same issue with a statically built
> kernel if the bootloader didn't enable it.

Noted. Will revise commit log.

>
>>
>> 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);
>
> You can probably use devm_clk_get to make the exit path smaller.

As it stands, the driver does not call clk_put in the exit path.
Using devm_clk_get here would be a good fix.

>
>> + if (IS_ERR(priv->stmmac_clk)) {
>> + pr_warn("%s: warning: cannot get CSR clock\n", __func__);
>
> And dev_warn here.
>
>> + 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);
>> +
>
> Hu? Why do you disable the clock? don't you need it afterwards?

The clock is enabled in *_open (when the network interface is used),
and disabled in *_close.


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