netdev - Re: [PATCH net-next 25/30] net: dsa: mt7530: properly set MT7531_CPU

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Message-ID: <9423a818-f9c0-d867-7f7d-27f05e1536b9@arinc9.com>
Date: Sun, 4 Jun 2023 11:21:48 +0300
From: Arınç ÜNAL <arinc.unal@...nc9.com>
To: Vladimir Oltean <olteanv@...il.com>
Cc: Sean Wang <sean.wang@...iatek.com>, Landen Chao
 <Landen.Chao@...iatek.com>, DENG Qingfang <dqfext@...il.com>,
 Daniel Golle <daniel@...rotopia.org>, Andrew Lunn <andrew@...n.ch>,
 Florian Fainelli <f.fainelli@...il.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Matthias Brugger <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Russell King <linux@...linux.org.uk>,
 Richard van Schagen <richard@...terhints.com>,
 Richard van Schagen <vschagen@...com>,
 Frank Wunderlich <frank-w@...lic-files.de>,
 Bartel Eerdekens <bartel.eerdekens@...stell8.be>, erkin.bozoglu@...ont.com,
 mithat.guner@...ont.com, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH net-next 25/30] net: dsa: mt7530: properly set
 MT7531_CPU_PMAP

On 26.05.2023 18:51, Vladimir Oltean wrote:
> On Mon, May 22, 2023 at 03:15:27PM +0300, arinc9.unal@...il.com wrote:
>> From: Arınç ÜNAL <arinc.unal@...nc9.com>
>>
>> Every bit of the CPU port bitmap for MT7531 and the switch on the MT7988
>> SoC represents a CPU port to trap frames to. Currently only the bit that
>> corresponds to the first found CPU port is set on the bitmap. Introduce the
>> MT7531_CPU_PMAP macro to individually set the bits of the CPU port bitmap.
>> Set the CPU port bitmap for MT7531 and the switch on the MT7988 SoC on
>> mt753x_cpu_port_enable() which runs on a loop for each CPU port. Add
>> comments to explain this.
>>
>> According to the document MT7531 Reference Manual for Development Board
>> v1.0, the MT7531_CPU_PMAP bits are unset after reset so no need to clear it
>> beforehand. Since there's currently no public document for the switch on
>> the MT7988 SoC, I assume this is also the case for this switch.
>>
>> Tested-by: Arınç ÜNAL <arinc.unal@...nc9.com>
>> Signed-off-by: Arınç ÜNAL <arinc.unal@...nc9.com>
>> ---
> 
> Is this supposed to be a bug fix? (incompatibility with past or future
> device trees also counts as bugs) If so, it needs a Fixes: tag and to be
> targeted towards the "net" tree. Also, the impact of the current behavior
> and of the change need to be explained better.

Yes, this fixes a bug for future devicetrees. I will send this to net 
with a more detailed explanation, thanks.

> 
>>   drivers/net/dsa/mt7530.c | 15 ++++++++-------
>>   drivers/net/dsa/mt7530.h |  3 ++-
>>   2 files changed, 10 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
>> index 58d8738d94d3..0b513e3628fe 100644
>> --- a/drivers/net/dsa/mt7530.c
>> +++ b/drivers/net/dsa/mt7530.c
>> @@ -963,6 +963,13 @@ mt753x_cpu_port_enable(struct dsa_switch *ds, int port)
>>   		mt7530_rmw(priv, MT753X_MFC, MT7530_CPU_MASK, MT7530_CPU_EN |
>>   			   MT7530_CPU_PORT(port));
>>   
>> +	/* Add the CPU port to the CPU port bitmap for MT7531 and the switch on
>> +	 * the MT7988 SoC. Any frames set for trapping to CPU port will be
>> +	 * trapped to the CPU port the user port is affine to.
>> +	 */
>> +	if (priv->id == ID_MT7531 || priv->id == ID_MT7988)
>> +		mt7530_set(priv, MT7531_CFC, MT7531_CPU_PMAP(BIT(port)));
>> +
> 
> Stylistically, the existence of an indirect call to priv->info->cpu_port_config()
> per switch family is a bit dissonant with an explicit check for device id later
> in the same function.

mt753x_cpu_port_enable() is not being called from 
priv->info->cpu_port_config() though. I'm not sure how I would do this 
without the device ID check here.

> 
>>   	/* CPU port gets connected to all user ports of
>>   	 * the switch.
>>   	 */
>> @@ -2315,15 +2322,9 @@ static int
>>   mt7531_setup_common(struct dsa_switch *ds)
>>   {
>>   	struct mt7530_priv *priv = ds->priv;
>> -	struct dsa_port *cpu_dp;
>>   	int ret, i;
>>   
>> -	/* BPDU to CPU port */
>> -	dsa_switch_for_each_cpu_port(cpu_dp, ds) {
>> -		mt7530_rmw(priv, MT7531_CFC, MT7531_CPU_PMAP_MASK,
>> -			   BIT(cpu_dp->index));
>> -		break;
>> -	}
>> +	/* Trap BPDUs to the CPU port(s) */
>>   	mt7530_rmw(priv, MT753X_BPC, MT753X_BPDU_PORT_FW_MASK,
>>   		   MT753X_BPDU_CPU_ONLY);
>>   
>> diff --git a/drivers/net/dsa/mt7530.h b/drivers/net/dsa/mt7530.h
>> index 5ebb942b07ef..fd2a2f726b8a 100644
>> --- a/drivers/net/dsa/mt7530.h
>> +++ b/drivers/net/dsa/mt7530.h
>> @@ -53,7 +53,8 @@ enum mt753x_id {
>>   #define  MT7531_MIRROR_MASK		(0x7 << 16)
>>   #define  MT7531_MIRROR_PORT_GET(x)	(((x) >> 16) & 0x7)
>>   #define  MT7531_MIRROR_PORT_SET(x)	(((x) & 0x7) << 16)
>> -#define  MT7531_CPU_PMAP_MASK		GENMASK(7, 0)
>> +#define  MT7531_CPU_PMAP(x)		((x) & 0xff)
> 
> You can leave this as ((x) & GENMASK(7, 0))

Now that I've read Russell's comment on the previous patch, the below 
would be even better?

MT7531_CPU_PMAP(x)		FIELD_PREP(MT7531_CPU_PMAP_MASK, x)

> 
>> +#define  MT7531_CPU_PMAP_MASK		MT7531_CPU_PMAP(~0)
> 
> There's no other user of MT7531_CPU_PMAP_MASK, you can remove this.

Should I do above or remove this?

Arınç