netdev - Re: [PATCH net-next 2/3] net: bcmgenet: Pass "main" clock down to the MDIO driver

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Date: Fri, 16 Feb 2024 14:50:19 -0800
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: Jacob Keller <jacob.e.keller@...el.com>, netdev@...r.kernel.org
Cc: Doug Berger <opendmb@...il.com>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>,
 Russell King <linux@...linux.org.uk>,
 open list <linux-kernel@...r.kernel.org>,
 Justin Chen <justin.chen@...adcom.com>
Subject: Re: [PATCH net-next 2/3] net: bcmgenet: Pass "main" clock down to the
 MDIO driver

On 2/16/24 14:41, Jacob Keller wrote:
> 
> 
> On 2/16/2024 10:42 AM, Florian Fainelli wrote:
>> GENET has historically had to create a MDIO platform device for its
>> controller and pass some auxiliary data to it, like a MDIO completion
>> callback. Now we also pass the "main" clock to allow for the MDIO bus
>> controller to manage that clock adequately around I/O accesses.
>>
>> Signed-off-by: Florian Fainelli <florian.fainelli@...adcom.com>
>> ---
>>   drivers/net/ethernet/broadcom/genet/bcmmii.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/broadcom/genet/bcmmii.c b/drivers/net/ethernet/broadcom/genet/bcmmii.c
>> index cbbe004621bc..7a21950da77c 100644
>> --- a/drivers/net/ethernet/broadcom/genet/bcmmii.c
>> +++ b/drivers/net/ethernet/broadcom/genet/bcmmii.c
>> @@ -476,6 +476,10 @@ static int bcmgenet_mii_register(struct bcmgenet_priv *priv)
>>   	ppd.wait_func = bcmgenet_mii_wait;
>>   	ppd.wait_func_data = priv;
>>   	ppd.bus_name = "bcmgenet MII bus";
>> +	/* Pass a reference to our "main" clock which is used for MDIO
>> +	 * transfers
>> +	 */
>> +	ppd.clk = priv->clk;
>>   
>>   	/* Unimac MDIO bus controller starts at UniMAC offset + MDIO_CMD
>>   	 * and is 2 * 32-bits word long, 8 bytes total.
> 
> Is this missing a modification of the header file to add the clk field
> to struct unimac_mdio_pdata? I don't see that field in the
> include/linux/platform_data/mdio-bcm-unimac.h header currently...
> 
> Oh. you included that in the first patch of the series. I see.

I suppose I could have included it in patch #1, and have introduced in 
patch #2 the hunk that dealt with fetching pdata->clk, but since I was 
re-organizing the mdio-bcm-unimac.c driver's probe function, it felt 
more natural to arrange it that way.

> 
> It feels like the series would be more natural of this was 1/3 instead
> of 2/3, since the current 1/3 patch depends on this clk value being set, no?

I sort of debated that with myself, and ended up going with: put the 
plumbing first, wire it later, rather than the opposite. If someone was 
to run a bisection there would not be any difference in behavior until 
patch #2 regardless of their ordering.

> 
> The result of the series makes sense tho:
> 
> Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>

Thanks Jacob!
-- 
Florian

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