netdev - Re: [PATCH v2 1/5] net: dsa: mv88e6xxx: introduce support for two chips using direct smi addressing

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Date:   Fri, 24 May 2019 13:54:07 -0400
From:   Vivien Didelot <vivien.didelot@...il.com>
To:     Rasmus Villemoes <rasmus.villemoes@...vas.dk>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Rasmus Villemoes <Rasmus.Villemoes@...vas.se>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] net: dsa: mv88e6xxx: introduce support for two
 chips using direct smi addressing

Hi Rasmus,

On Fri, 24 May 2019 09:00:24 +0000, Rasmus Villemoes <rasmus.villemoes@...vas.dk> wrote:
> The 88e6250 (as well as 6220, 6071, 6070, 6020) do not support
> multi-chip (indirect) addressing. However, one can still have two of
> them on the same mdio bus, since the device only uses 16 of the 32
> possible addresses, either addresses 0x00-0x0F or 0x10-0x1F depending
> on the ADDR4 pin at reset [since ADDR4 is internally pulled high, the
> latter is the default].
> 
> In order to prepare for supporting the 88e6250 and friends, introduce
> mv88e6xxx_info::dual_chip to allow having a non-zero sw_addr while
> still using direct addressing.
> 
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@...vas.dk>
> ---
>  drivers/net/dsa/mv88e6xxx/chip.h |  6 ++++++
>  drivers/net/dsa/mv88e6xxx/smi.c  | 25 ++++++++++++++++++++++++-
>  2 files changed, 30 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/dsa/mv88e6xxx/chip.h b/drivers/net/dsa/mv88e6xxx/chip.h
> index faa3fa889f19..74777c3bc313 100644
> --- a/drivers/net/dsa/mv88e6xxx/chip.h
> +++ b/drivers/net/dsa/mv88e6xxx/chip.h
> @@ -112,6 +112,12 @@ struct mv88e6xxx_info {
>  	 * when it is non-zero, and use indirect access to internal registers.
>  	 */
>  	bool multi_chip;
> +	/* Dual-chip Addressing Mode
> +	 * Some chips respond to only half of the 32 SMI addresses,
> +	 * allowing two to coexist on the same SMI interface.
> +	 */
> +	bool dual_chip;
> +
>  	enum dsa_tag_protocol tag_protocol;
>  
>  	/* Mask for FromPort and ToPort value of PortVec used in ATU Move
> diff --git a/drivers/net/dsa/mv88e6xxx/smi.c b/drivers/net/dsa/mv88e6xxx/smi.c
> index 96f7d2685bdc..1151b5b493ea 100644
> --- a/drivers/net/dsa/mv88e6xxx/smi.c
> +++ b/drivers/net/dsa/mv88e6xxx/smi.c
> @@ -24,6 +24,10 @@
>   * When ADDR is non-zero, the chip uses Multi-chip Addressing Mode, allowing
>   * multiple devices to share the SMI interface. In this mode it responds to only
>   * 2 registers, used to indirectly access the internal SMI devices.
> + *
> + * Some chips use a different scheme: Only the ADDR4 pin is used for
> + * configuration, and the device responds to 16 of the 32 SMI
> + * addresses, allowing two to coexist on the same SMI interface.
>   */
>  
>  static int mv88e6xxx_smi_direct_read(struct mv88e6xxx_chip *chip,
> @@ -76,6 +80,23 @@ static const struct mv88e6xxx_bus_ops mv88e6xxx_smi_direct_ops = {
>  	.write = mv88e6xxx_smi_direct_write,
>  };
>  
> +static int mv88e6xxx_smi_dual_direct_read(struct mv88e6xxx_chip *chip,
> +					  int dev, int reg, u16 *data)
> +{
> +	return mv88e6xxx_smi_direct_read(chip, dev + chip->sw_addr, reg, data);

Using chip->sw_addr + dev seems more idiomatic to me than dev + chip->sw_addr.

> +}
> +
> +static int mv88e6xxx_smi_dual_direct_write(struct mv88e6xxx_chip *chip,
> +					   int dev, int reg, u16 data)
> +{
> +	return mv88e6xxx_smi_direct_write(chip, dev + chip->sw_addr, reg, data);
> +}
> +
> +static const struct mv88e6xxx_bus_ops mv88e6xxx_smi_dual_direct_ops = {
> +	.read = mv88e6xxx_smi_dual_direct_read,
> +	.write = mv88e6xxx_smi_dual_direct_write,
> +};
> +
>  /* Offset 0x00: SMI Command Register
>   * Offset 0x01: SMI Data Register
>   */
> @@ -144,7 +165,9 @@ static const struct mv88e6xxx_bus_ops mv88e6xxx_smi_indirect_ops = {
>  int mv88e6xxx_smi_init(struct mv88e6xxx_chip *chip,
>  		       struct mii_bus *bus, int sw_addr)
>  {
> -	if (sw_addr == 0)
> +	if (chip->info->dual_chip)
> +		chip->smi_ops = &mv88e6xxx_smi_dual_direct_ops;
> +	else if (sw_addr == 0)
>  		chip->smi_ops = &mv88e6xxx_smi_direct_ops;
>  	else if (chip->info->multi_chip)
>  		chip->smi_ops = &mv88e6xxx_smi_indirect_ops;

Please submit respins (v2, v3, and so on) as independent threads,
not as a reply to the previous version.

Otherwise this looks good to me:

Reviewed-by: Vivien Didelot <vivien.didelot@...il.com>

Thanks,
Vivien