Re: [PATCH net v2 5/5] net: dsa: b53: do not touch DLL_IQQD on bcm53115

[Paolo Abeni <pabeni@redhat.com>]

On 6/3/25 8:15 AM, Jonas Gorski wrote:
> On Mon, Jun 2, 2025 at 11:40 PM Florian Fainelli
> <florian.fainelli@broadcom.com> wrote:
>> On 6/2/25 12:39, Jonas Gorski wrote:
>>> According to OpenMDK, bit 2 of the RGMII register has a different
>>> meaning for BCM53115 [1]:
>>>
>>> "DLL_IQQD         1: In the IDDQ mode, power is down0: Normal function
>>>                    mode"
>>>
>>> Configuring RGMII delay works without setting this bit, so let's keep it
>>> at the default. For other chips, we always set it, so not clearing it
>>> is not an issue.
>>>
>>> One would assume BCM53118 works the same, but OpenMDK is not quite sure
>>> what this bit actually means [2]:
>>>
>>> "BYPASS_IMP_2NS_DEL #1: In the IDDQ mode, power is down#0: Normal
>>>                      function mode1: Bypass dll65_2ns_del IP0: Use
>>>                      dll65_2ns_del IP"
>>>
>>> So lets keep setting it for now.
>>>
>>> [1] https://github.com/Broadcom-Network-Switching-Software/OpenMDK/blob/master/cdk/PKG/chip/bcm53115/bcm53115_a0_defs.h#L19871
>>> [2] https://github.com/Broadcom-Network-Switching-Software/OpenMDK/blob/master/cdk/PKG/chip/bcm53118/bcm53118_a0_defs.h#L14392
>>>
>>> Fixes: 967dd82ffc52 ("net: dsa: b53: Add support for Broadcom RoboSwitch")
>>> Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
>>> ---
>>> v1 -> v2:
>>> * new patch
>>>
>>>   drivers/net/dsa/b53/b53_common.c | 8 +++++---
>>>   1 file changed, 5 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
>>> index be4493b769f4..862bdccb7439 100644
>>> --- a/drivers/net/dsa/b53/b53_common.c
>>> +++ b/drivers/net/dsa/b53/b53_common.c
>>> @@ -1354,8 +1354,7 @@ static void b53_adjust_531x5_rgmii(struct dsa_switch *ds, int port,
>>>        * tx_clk aligned timing (restoring to reset defaults)
>>>        */
>>>       b53_read8(dev, B53_CTRL_PAGE, off, &rgmii_ctrl);
>>> -     rgmii_ctrl &= ~(RGMII_CTRL_DLL_RXC | RGMII_CTRL_DLL_TXC |
>>> -                     RGMII_CTRL_TIMING_SEL);
>>> +     rgmii_ctrl &= ~(RGMII_CTRL_DLL_RXC | RGMII_CTRL_DLL_TXC);
>>
>> Are not we missing a:
>>
>> if (dev->chip_id != BCM53115_DEVICE_ID)
>>         rgmii_ctrl &= ~RGMII_CTRL_TIMING_SEL;
>>
>> here to be strictly identical before/after?
> 
> We could add it for symmetry, but it would be purely decorational. We
> unconditionally set this bit again later, so clearing it before has no
> actual effect, which is why I didn't add it.

Makes sense, and the code in this patch is IMHO more readable.

/P