[PATCH net v1] net: dsa: ksz8795: use correct number of physical ports

[PATCH net v1] net: dsa: ksz8795: use correct number of physical ports

[Sven Van Asbroeck]

From: Sven Van Asbroeck <thesven73@gmail.com>

The ksz8795 has five physical ports, but the driver assumes
it has only four. This prevents the driver from working correctly.

Fix by indicating the correct number of physical ports.

Fixes: e66f840c08a23 ("net: dsa: ksz: Add Microchip KSZ8795 DSA driver")
Tested-by: Sven Van Asbroeck <thesven73@gmail.com> # ksz8795
Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com>
---

Tree: git://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git # 39e367766fe1

To: Woojung Huh <woojung.huh@microchip.com>
To: Andrew Lunn <andrew@lunn.ch>
To: Vivien Didelot <vivien.didelot@gmail.com>
To: Florian Fainelli <f.fainelli@gmail.com>
To: Vladimir Oltean <olteanv@gmail.com>
To: "David S. Miller" <davem@davemloft.net>
To: Jakub Kicinski <kuba@kernel.org>
Cc: Marek Vasut <marex@denx.de>
Cc: Tristram Ha <Tristram.Ha@microchip.com>
Cc: Microchip Linux Driver Support <UNGLinuxDriver@microchip.com>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org (open list)

 drivers/net/dsa/microchip/ksz8795.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/dsa/microchip/ksz8795.c b/drivers/net/dsa/microchip/ksz8795.c
index 1e101ab56cea..367cebe37ae6 100644
--- a/drivers/net/dsa/microchip/ksz8795.c
+++ b/drivers/net/dsa/microchip/ksz8795.c
@@ -1194,7 +1194,7 @@ static const struct ksz_chip_data ksz8795_switch_chips[] = {
 		.num_alus = 0,
 		.num_statics = 8,
 		.cpu_ports = 0x10,	/* can be configured as cpu port */
-		.port_cnt = 4,		/* total physical port count */
+		.port_cnt = 5,		/* total physical port count */
 	},
 	{
 		.chip_id = 0x8794,
-- 
2.17.1

Re: [PATCH net v1] net: dsa: ksz8795: use correct number of physical ports

[Florian Fainelli]

On 12/3/2020 1:46 PM, Sven Van Asbroeck wrote:
> From: Sven Van Asbroeck <thesven73@gmail.com>
> 
> The ksz8795 has five physical ports, but the driver assumes
> it has only four. This prevents the driver from working correctly.
> 
> Fix by indicating the correct number of physical ports.
> 
> Fixes: e66f840c08a23 ("net: dsa: ksz: Add Microchip KSZ8795 DSA driver")
> Tested-by: Sven Van Asbroeck <thesven73@gmail.com> # ksz8795
> Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
-- 
Florian

Re: [PATCH net v1] net: dsa: ksz8795: use correct number of physical ports

[Jakub Kicinski]

On Thu,  3 Dec 2020 16:46:45 -0500 Sven Van Asbroeck wrote:
> From: Sven Van Asbroeck <thesven73@gmail.com>
> 
> The ksz8795 has five physical ports, but the driver assumes
> it has only four. This prevents the driver from working correctly.
> 
> Fix by indicating the correct number of physical ports.
> 
> Fixes: e66f840c08a23 ("net: dsa: ksz: Add Microchip KSZ8795 DSA driver")
> Tested-by: Sven Van Asbroeck <thesven73@gmail.com> # ksz8795
> Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com>

All the port counts here are -1 compared to datasheets, so I'm assuming
the are not supposed to include the host facing port or something?

Can you describe the exact problem you're trying to solve?

DSA devices are not supposed to have a netdev for the host facing port
on the switch (sorry for stating the obvious).

> diff --git a/drivers/net/dsa/microchip/ksz8795.c b/drivers/net/dsa/microchip/ksz8795.c
> index 1e101ab56cea..367cebe37ae6 100644
> --- a/drivers/net/dsa/microchip/ksz8795.c
> +++ b/drivers/net/dsa/microchip/ksz8795.c
> @@ -1194,7 +1194,7 @@ static const struct ksz_chip_data ksz8795_switch_chips[] = {
>  		.num_alus = 0,
>  		.num_statics = 8,
>  		.cpu_ports = 0x10,	/* can be configured as cpu port */
> -		.port_cnt = 4,		/* total physical port count */
> +		.port_cnt = 5,		/* total physical port count */
>  	},
>  	{
>  		.chip_id = 0x8794,

Re: [PATCH net v1] net: dsa: ksz8795: use correct number of physical ports

[Andrew Lunn]

On Fri, Dec 04, 2020 at 03:24:56PM -0800, Jakub Kicinski wrote:
> On Thu,  3 Dec 2020 16:46:45 -0500 Sven Van Asbroeck wrote:
> > From: Sven Van Asbroeck <thesven73@gmail.com>
> > 
> > The ksz8795 has five physical ports, but the driver assumes
> > it has only four. This prevents the driver from working correctly.
> > 
> > Fix by indicating the correct number of physical ports.
> > 
> > Fixes: e66f840c08a23 ("net: dsa: ksz: Add Microchip KSZ8795 DSA driver")
> > Tested-by: Sven Van Asbroeck <thesven73@gmail.com> # ksz8795
> > Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com>
> 
> All the port counts here are -1 compared to datasheets, so I'm assuming
> the are not supposed to include the host facing port or something?
> 
> Can you describe the exact problem you're trying to solve?
> 
> DSA devices are not supposed to have a netdev for the host facing port
> on the switch (sorry for stating the obvious).

Hi Jakub

It is the DSA core layer which takes care of that creating/not
creating netdevs. The switch should declare all the ports it has.

There has been issues with the ksz collection of drivers having
different meanings for port_cnt. There recently was some changes in
this area, maybe it broke something?

     Andrew

Re: [PATCH net v1] net: dsa: ksz8795: use correct number of physical ports

[Sven Van Asbroeck]

Jakub, Andrew,

On Fri, Dec 4, 2020 at 6:24 PM Jakub Kicinski <kuba@kernel.org> wrote:
>
> All the port counts here are -1 compared to datasheets, so I'm assuming
> the are not supposed to include the host facing port or something?
>
> Can you describe the exact problem you're trying to solve?
>

The ksz8795 driver refuses to accept my devicetree (see below). It doesn't like
the presence of the cpu node. But I really need a cpu node, because phy-mode is
crucially important to my application: without phy-mode = "rgmii-id", the
ksz8795's ingress bit does not get set, and communication fails.

I was already suspicious of my fix: why would such an important chip property
be wrong? But changing it was very seductive: after all, the ksz8795's headline
is "Integrated 5-Port 10/100-Managed Ethernet Switch", and the driver code says
this:

        .port_cnt = 4,          /* total physical port count */

I can see now that this should be fixed more generally. The of parsing code
is using the wrong port count variable. I'll submit that shortly.

That said, when I look at this driver, I get very confused between port_cnt,
num_ports, and whether they include or exclude the cpu port. Until this gets
cleaned up, maybe the comment above can be improved, so developers don't get
too confused at least? I'll submit a patch for that too.

ethernet-switch@0 {
        compatible = "microchip,ksz8795";
        spi-max-frequency = <1000000>;
        reg = <0>;

        ports {
                #address-cells = <1>;
                #size-cells = <0>;
                port@0 {
                        reg = <0>;
                        label = "lan1";
                };
                port@1 {
                        reg = <1>;
                        label = "lan2";
                };
                port@2 {
                        reg = <2>;
                        label = "lan3";
                };
                port@3 {
                        reg = <3>;
                        label = "lan4";
                };
                port@4 {
                        /* driver errors out because
                         * reg >= dev->port_cnt (4)
                         */
                        reg = <4>;
                        label = "cpu";
                        ethernet = <&something>;
                        phy-mode = "rgmii-id";
                        fixed-link {
                                speed = <1000>;
                                full-duplex;
                        };
                };
        };
};