netdev - Re: [PATCH 3/4] net: mvmdio: print warning when orion-mdio has too many clocks

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Message-ID: <8d24d716-2f64-37d3-a7f2-1725d48c7d5f@solid-run.com>
Date:   Sat, 6 Jul 2019 18:21:34 +0200
From:   Josua Mayer <josua@...id-run.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 3/4] net: mvmdio: print warning when orion-mdio has too
 many clocks

Hi Andrew,

Am 06.07.19 um 18:09 schrieb Andrew Lunn:
> On Sat, Jul 06, 2019 at 05:18:59PM +0200, josua@...id-run.com wrote:
>> From: Josua Mayer <josua@...id-run.com>
>>
>> Print a warning when device tree specifies more than the maximum of four
>> clocks supported by orion-mdio. Because reading from mdio can lock up
>> the Armada 8k when a required clock is not initialized, it is important
>> to notify the user when a specified clock is ignored.
>>
>> Signed-off-by: Josua Mayer <josua@...id-run.com>
>> ---
>>  drivers/net/ethernet/marvell/mvmdio.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/marvell/mvmdio.c b/drivers/net/ethernet/marvell/mvmdio.c
>> index e17d563e97a6..89a99bf8e87b 100644
>> --- a/drivers/net/ethernet/marvell/mvmdio.c
>> +++ b/drivers/net/ethernet/marvell/mvmdio.c
>> @@ -326,6 +326,10 @@ static int orion_mdio_probe(struct platform_device *pdev)
>>  		clk_prepare_enable(dev->clk[i]);
>>  	}
>>  
>> +	if (!IS_ERR(of_clk_get(pdev->dev.of_node, i)))
>> +		dev_warn(dev, "unsupported number of clocks, limiting to the first "
>> +			 __stringify(ARRAY_SIZE(dev->clk)) "\n");
>> +
> Hi Josua
>
> Humm. Say getting clock 0 returned -EINVAL, or some other error code.
> We break out of the loop, since such errors are being ignored. We then
> hit this new code. Getting clock 1 works, and then we incorrectly
> print this message.

Good point about breaking out of the loop! I did indeed not take the
break condition of the loop into account.

I can not exactly follow your example though. The first failure of
of_clk_get will trigger break and exit the loop,
and then we would indeed print the wrong message ... .

>
> Rather than getting the i'th clock, get ARRAY_SIZE(dev->clk)'th clock.
I will gladly make the change in a v2.
>        Andrew

-
Josua