From: Hans-Frieder Vogt <hfdevel@gmx.net>
To: Andrew Lunn <andrew@lunn.ch>,
FUJITA Tomonori <fujita.tomonori@gmail.com>
Cc: netdev@vger.kernel.org, horms@kernel.org, kuba@kernel.org,
jiri@resnulli.us, pabeni@redhat.com
Subject: Re: [PATCH net-next v5 5/6] net: tn40xx: add mdio bus support
Date: Thu, 9 May 2024 11:52:46 +0200 [thread overview]
Message-ID: <6388dcc8-2152-45bd-8e0f-2fb558c6fce9@gmx.net> (raw)
In-Reply-To: <71d4a673-73b6-4ebe-a669-de3ae6c9af5f@gmx.net>
On 08.05.2024 21.30, Hans-Frieder Vogt wrote:
> On 08.05.2024 20.25, Andrew Lunn wrote:
>>>> + writel(((1 << 15) | i), regs + TN40_REG_MDIO_CMD);
>>> similarly here:
>>>
>>> writel((MDIO_PHY_ID_C45 | i), regs + TN40_REG_MDIO_CMD);
>> This one i don't agree with. It happens to work, but there is no
>> reason to think the hardware has been designed around how Linux
>> combines the different parts of a C45 address into one word, using the
>> top bit to indicate it is actually a C45 address, not a C22.
>>
>> I would much prefer a TN40_ define is added for this bit.
> OK, yes, very valid point.
A small addition here:
digging through an old Tehuti linux river for the TN30xx (revision
7.33.5.1) I found revealing comments:
in bdx_mdio_read:
/* Write read command */
writel(MDIO_CMD_STAT_VAL(1, device, port), regs +
regMDIO_CMD_STAT);
in bdx_mdio_write:
/* Write write command */
writel(MDIO_CMD_STAT_VAL(0, device, port), regs +
regMDIO_CMD_STAT);
The CMD register has a different layout in the TN40xx, but the logic is
similar.
Therefore, I conclude now that the value (1 << 15) is in fact a read
flag. Maybe it could be defined like:
#define TN40_MDIO_READ BIT(15)
>>
>>>> + writel(((device & 0x1F) | ((port & 0x1F) << 5)),
>>> and also here, similarly:
>>>
>>> writel((device & MDIO_PHY_ID_DEVAD) | ((port << 5) &
>>> MDIO_PHY_ID_PRTAD),
>> Similarly here, this happens to work, but that is just because the
>> hardware matches a software construct Linux uses. It would be better
>> to add TN40_ macros to describe the hardware.
> agreed, I assume I just interpreted too much into the constants.
>>
>> Andrew
>
> Thanks!
> Hans
>
Thanks for challenging my initial assumptions,
Hans
next prev parent reply other threads:[~2024-05-09 9:52 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-08 18:08 [PATCH net-next v5 5/6] net: tn40xx: add mdio bus support Hans-Frieder Vogt
2024-05-08 18:25 ` Andrew Lunn
2024-05-08 19:30 ` Hans-Frieder Vogt
2024-05-09 9:52 ` Hans-Frieder Vogt [this message]
2024-05-09 10:59 ` FUJITA Tomonori
2024-05-09 11:16 ` Hans-Frieder Vogt
2024-05-09 11:25 ` FUJITA Tomonori
-- strict thread matches above, loose matches on Subject: below --
2024-05-08 11:39 [PATCH net-next v5 0/6] add ethernet driver for Tehuti Networks TN40xx chips FUJITA Tomonori
2024-05-08 11:39 ` [PATCH net-next v5 5/6] net: tn40xx: add mdio bus support FUJITA Tomonori
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