netdev - Re: [PATCH net v2 5/5] net: dsa: b53: do not touch DLL

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <ae51482c-1bd3-4e2e-a02f-d5ddda55f0d2@broadcom.com>
Date: Thu, 5 Jun 2025 11:01:17 -0700
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: Paolo Abeni <pabeni@...hat.com>, Jonas Gorski <jonas.gorski@...il.com>,
 Florian Fainelli <florian.fainelli@...adcom.com>
Cc: Andrew Lunn <andrew@...n.ch>, Vladimir Oltean <olteanv@...il.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Vivien Didelot <vivien.didelot@...il.com>,
 Álvaro Fernández Rojas <noltari@...il.com>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v2 5/5] net: dsa: b53: do not touch DLL_IQQD on
 bcm53115

On 6/5/25 02:06, Paolo Abeni wrote:
> On 6/3/25 8:15 AM, Jonas Gorski wrote:
>> On Mon, Jun 2, 2025 at 11:40 PM Florian Fainelli
>> <florian.fainelli@...adcom.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@...il.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.

Agreed, thanks for taking those patches.
-- 
Florian