netdev - Re: [PATCH 3/5] net: dsa: ksz: Factor out common tag code

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Date:   Thu, 13 Dec 2018 04:42:58 +0100
From:   Marek Vasut <marex@...x.de>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org, f.fainelli@...il.com,
        vivien.didelot@...oirfairelinux.com, Woojung.Huh@...rochip.com,
        UNGLinuxDriver@...rochip.com,
        Tristram Ha <Tristram.Ha@...rochip.com>,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH 3/5] net: dsa: ksz: Factor out common tag code

On 12/08/2018 12:34 PM, Andrew Lunn wrote:
> On Fri, Dec 07, 2018 at 07:18:43PM +0100, Marek Vasut wrote:
>> From: Tristram Ha <Tristram.Ha@...rochip.com>
>>
>> Factor out common code from the tag_ksz , so that the code can be used
>> with other KSZ family switches which use differenly sized tags.
> 
> I prefer this implementation over what Tristram recently submitted. It
> is also what we suggested a while back. However, since then we have
> had Spectra/meltdown, and we now know a function call through a
> pointer is expensive. This is the hot path, every frame comes through
> here, so it is worth taking the time to optimize this. Could you try
> to remove the ksz_tag_ops structure. xmit looks simple, since it is a
> tail call, so you can do that in ksz9477_xmit. Receive looks a bit
> more complex.

They're both simple in the end, I'll send V2 once I test it a bit.

> I also think for the moment we need it ignore PTP until we have the
> big picture sorted out. If need be, the code can be refactored yet
> again. But i don't want PTP holding up getting more switches
> supported.
> 
>> Signed-off-by: Tristram Ha <Tristram.Ha@...rochip.com>
>> Signed-off-by: Marek Vasut <marex@...x.de>
>> Cc: Vivien Didelot <vivien.didelot@...oirfairelinux.com>
>> Cc: Woojung Huh <woojung.huh@...rochip.com>
>> Cc: David S. Miller <davem@...emloft.net>
>> ---
>>  net/dsa/tag_ksz.c | 125 +++++++++++++++++++++++++++++++++-------------
>>  1 file changed, 90 insertions(+), 35 deletions(-)
>>
>> diff --git a/net/dsa/tag_ksz.c b/net/dsa/tag_ksz.c
>> index 036bc62198f28..d94bad1ab7e53 100644
>> --- a/net/dsa/tag_ksz.c
>> +++ b/net/dsa/tag_ksz.c
>> @@ -14,34 +14,30 @@
>>  #include <net/dsa.h>
>>  #include "dsa_priv.h"
>>  
>> -/* For Ingress (Host -> KSZ), 2 bytes are added before FCS.
>> - * ---------------------------------------------------------------------------
>> - * DA(6bytes)|SA(6bytes)|....|Data(nbytes)|tag0(1byte)|tag1(1byte)|FCS(4bytes)
>> - * ---------------------------------------------------------------------------
>> - * tag0 : Prioritization (not used now)
>> - * tag1 : each bit represents port (eg, 0x01=port1, 0x02=port2, 0x10=port5)
>> - *
>> - * For Egress (KSZ -> Host), 1 byte is added before FCS.
>> - * ---------------------------------------------------------------------------
>> - * DA(6bytes)|SA(6bytes)|....|Data(nbytes)|tag0(1byte)|FCS(4bytes)
>> - * ---------------------------------------------------------------------------
>> - * tag0 : zero-based value represents port
>> - *	  (eg, 0x00=port1, 0x02=port3, 0x06=port7)
>> - */
>> +struct ksz_tag_ops {
>> +	void	(*get_tag)(u8 *tag, unsigned int *port, unsigned int *len);
>> +	void	(*set_tag)(struct sk_buff *skb, struct net_device *dev);
>> +};
>>  
>> -#define	KSZ_INGRESS_TAG_LEN	2
>> -#define	KSZ_EGRESS_TAG_LEN	1
>> +/* Typically only one byte is used for tail tag. */
>> +#define KSZ_EGRESS_TAG_LEN		1
>>  
>> -static struct sk_buff *ksz_xmit(struct sk_buff *skb, struct net_device *dev)
>> +/* Frames with following addresse may need to be sent even when the port is
>> + * closed.
>> + */
>> +static const u8 special_mult_addr[] = {
>> +	0x01, 0x80, 0xC2, 0x00, 0x00, 0x00
>> +};
>> +
> 
> This is new functionality, not part of the refactoring the
> code. Please add that as a new patch. Also, you can probably make use
> of is_link_local_ether_addr().

Sounds good, will do in V2.

-- 
Best regards,
Marek Vasut