From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
To: Wolfram Sang <wsa@kernel.org>,
Chris Packham <chris.packham@alliedtelesis.co.nz>,
krzysztof.kozlowski+dt@linaro.org, gregory.clement@bootlin.com,
andi.shyti@kernel.org, robh+dt@kernel.org, conor+dt@kernel.org,
linux-i2c@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org, Abel Vesa <abel.vesa@linaro.org>
Subject: Re: [PATCH v5 1/2] dt-bindings: i2c: mv64xxx: add bus-reset-gpios property
Date: Fri, 27 Oct 2023 13:25:56 +0200 [thread overview]
Message-ID: <7bfa2f6c-3e99-49a6-9b5a-81398d4bce7e@linaro.org> (raw)
In-Reply-To: <ZTt+ZgNe5Y35E/C2@shikoro>
On 27/10/2023 11:09, Wolfram Sang wrote:
> On Fri, Oct 27, 2023 at 04:31:03PM +1300, Chris Packham wrote:
>> Add bus-reset-gpios and bus-reset-duration-us properties to the
>> marvell,mv64xxx-i2c binding. These can be used to describe hardware
>> where a common reset GPIO is connected to all downstream devices on and
>> I2C bus. This reset will be asserted then released before the downstream
>> devices on the bus are probed.
>>
>> Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
>> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
>
> Krzysztof, are you fine with this change?
Actually no. NAK.
Not because of the naming, but because the new name triggered some new
paths in my brain which brought the point - this is old problem of power
sequencing of children.
I believe this must be solved in more generic way. First - generic for
all I2C devices. Second - generic also matching other buses/subsystems,
which have similar problem. We did it for USB (onboard USB), MMC
(unloved MMC power sequence) and now we are doing it for PCIe and few
others (Cc: Abel)
https://lpc.events/event/17/contributions/1507/
Current solution is heavily limited. What about regulators? What about
buses having 2 reset lines (still the same bus)? What about sequence?
Best regards,
Krzysztof
next prev parent reply other threads:[~2023-10-27 11:26 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-27 3:31 [PATCH v5 0/2] i2c: mv64xxx: bus-reset-gpios Chris Packham
2023-10-27 3:31 ` [PATCH v5 1/2] dt-bindings: i2c: mv64xxx: add bus-reset-gpios property Chris Packham
2023-10-27 9:09 ` Wolfram Sang
2023-10-27 11:25 ` Krzysztof Kozlowski [this message]
2023-10-27 19:22 ` Rob Herring
2023-10-28 7:51 ` Krzysztof Kozlowski
2023-10-27 3:31 ` [PATCH v5 2/2] i2c: mv64xxx: add an optional " Chris Packham
2023-10-27 8:48 ` Andi Shyti
2023-10-27 11:27 ` Krzysztof Kozlowski
2023-10-27 11:37 ` Krzysztof Kozlowski
2023-10-29 20:48 ` Chris Packham
2023-10-31 6:01 ` Krzysztof Kozlowski
2023-10-31 19:59 ` Chris Packham
[not found] ` <20231027125537.5d5cu3wc4r4c2yb4@zenone.zhora.eu>
2023-10-29 21:02 ` Chris Packham
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