Date:   Thu, 1 Sep 2022 08:51:44 +0000
From:   <Arun.Ramadoss@...rochip.com>
To:     <o.rempel@...gutronix.de>, <olteanv@...il.com>
CC:     <andrew@...n.ch>, <linux-kernel@...r.kernel.org>,
        <UNGLinuxDriver@...rochip.com>, <vivien.didelot@...il.com>,
        <san@...v.dk>, <linux@...linux.org.uk>, <f.fainelli@...il.com>,
        <kuba@...nel.org>, <edumazet@...gle.com>, <pabeni@...hat.com>,
        <netdev@...r.kernel.org>, <Woojung.Huh@...rochip.com>,
        <davem@...emloft.net>
Subject: Re: [Patch net-next v2 0/9] net: dsa: microchip: add support for
 phylink mac config and link up

On Wed, 2022-08-31 at 18:10 +0200, Oleksij Rempel wrote:
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> 
> On Wed, Aug 31, 2022 at 06:18:59PM +0300, Vladimir Oltean wrote:
> > On Wed, Aug 31, 2022 at 09:43:24AM +0200, Oleksij Rempel wrote:
> > > > > Should we point them to ksz8795_xmii_ctrl0 and
> > > > > ksz8795_xmii_ctrl1? I don't know.
> > > > > Could you find out what these should be set to?
> > > > 
> > > > xmii_ctrl0/1 are missing and it make no sense to add it.
> > > > KSZ8873 switch is controlling CPU port MII configuration over
> > > > global,
> > > > not port based register.
> > > > 
> > > > I'll better define separate ops for this chip.
> > > 
> > > Hm, not only KSZ8830/KSZ8863/KSZ8873 are affected. ksz8795
> > > compatible
> > > series with defined .xmii_ctrl0/.xmii_ctrl1 are broken too.
> > > Because it
> > > is writing to the global config register over ksz_pwrite8
> > > function. It
> > > means, we are writing to 0xa6 instead of 0x06. And to 0xf6
> > > instead of
> > > 0x56.
> > What do you mean by "global config register"? The Is_1Gbps bit is
> > still
> > part of a port register, it's just that this particular register is
> > only
> > defined for the 5th port (port #4, the only xMII port on KSZ7895
> > AFAIU).
> > That doesn't necessarily make it a "global" register.
> > 
> > Datasheet says:
> > 
> > Register 22 (0x16): Reserved
> > Register 38 (0x26): Reserved
> > Register 54 (0x36): Reserved
> > Register 70 (0x46): Reserved
> > Register 86 (0x56): Port 5 Interface Control 6
> > 
> > I wonder if it's ok to modify the regs table like this, because we
> > should then only touch P_XMII_CTRL_1 using port 4:
> > 
> >  static const u16 ksz8795_regs[] = {
> >       [REG_IND_CTRL_0]                = 0x6E,
> >       [REG_IND_DATA_8]                = 0x70,
> >       [REG_IND_DATA_CHECK]            = 0x72,
> >       [REG_IND_DATA_HI]               = 0x71,
> >       [REG_IND_DATA_LO]               = 0x75,
> >       [REG_IND_MIB_CHECK]             = 0x74,
> >       [REG_IND_BYTE]                  = 0xA0,
> >       [P_FORCE_CTRL]                  = 0x0C,
> >       [P_LINK_STATUS]                 = 0x0E,
> >       [P_LOCAL_CTRL]                  = 0x07,
> >       [P_NEG_RESTART_CTRL]            = 0x0D,
> >       [P_REMOTE_STATUS]               = 0x08,
> >       [P_SPEED_STATUS]                = 0x09,
> >       [S_TAIL_TAG_CTRL]               = 0x0C,
> >       [P_STP_CTRL]                    = 0x02,
> >       [S_START_CTRL]                  = 0x01,
> >       [S_BROADCAST_CTRL]              = 0x06,
> >       [S_MULTICAST_CTRL]              = 0x04,
> >       [P_XMII_CTRL_0]                 = 0x06,
> > -     [P_XMII_CTRL_1]                 = 0x56,
> > +     [P_XMII_CTRL_1]                 = 0x06,
> >  };
> > 
> 
> Speed configuration on ksz8795 is done over two registers:
> Register 86 (0x56): Port 5 Interface Control 6: Is_1Gbps - BIT(6)
> and
> Register 6 (0x06): Global Control 4: Switch SW5-MII/RMII Speed
> -BIT(4)
> 
> both are accessed on wrong offsets.
> 
> I would prefer to do following steps:
> - remove everything from ksz_phylink_mac_link_up() except of
>   dev->dev_ops->phylink_mac_link_up
> - move ksz_duplex_flowctrl(), ksz_port_set_xmii_speed()... to
> ksz9477.c
>   and rename them. Assign ksz9477_phylink_mac_link_up()
>   dev->dev_ops->phylink_mac_link_up
> - create separate function ksz8795_phylink_mac_link_up()
> - use documented, not generic register names.
> 

In the original code, the ksz8795_cpu_interface_select (which does the
xmii and speed configuration) is called only ksz87xx switch not for the
ksz88x3.
During refactoring, I intentionally did not add the P_XMII_CTRL0/1 for
the ksz88xx in the chip_data structure.
I added check that if switch belong to ksz88x3 then return in the
phylink_mac_config function but I missed to add in the
phylink_mac_link_up. Thats the mistake I have done. So, for the ksz88xx
switch code breakage, it could be fixed by adding the check in the
phylink_mac_link_up as well.

For the code breakage in ksz8795/ksz8794, the original code has only
provision for configuring xmii mode and choosing the 100/1000Mbps speed
selection which could be selected using is_1Gbps bit of
port5_interface_control6 register (0x56). But it didn't have provision
to select speed between 10/100Mbps, flow control and duplex.

As per vladimir suggestion, P_XMII_CTRL1 can be changed from 0x56 to
0x06. It fixes the problem for ksz_set_xmii, ksz_set_gbit since this is
the port based register not the global register.

The global register 0x06 responsibilities are bit 4 for 10/100mbps
speed selection, bit 5 for flow control and bit 6  for duplex
operation. Since these three are new features added during refactoring
I overlooked it. 
To fix this, either I need to return from the ksz_set_100_10mbit &
ksz_duplex_flowctrl function if the chip_id is ksz87xx or add dev-
>dev_ops for this alone. 
Kindly suggest on how to proceed.



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