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From: Andi Shyti <andi.shyti@kernel.org>
To: Hardik Prakash <hardikprakash.official@gmail.com>
Cc: linux-i2c@vger.kernel.org, linux-gpio@vger.kernel.org,
	wsa@kernel.org,  andriy.shevchenko@intel.com,
	mario.limonciello@amd.com, brgl@bgdev.pl,
	 basavaraj.natikar@amd.com, linusw@kernel.org, nathan@kernel.org,
	 chaitanya.kumar.borah@intel.com, linux@leemhuis.info,
	regressions@leemhuis.info,  linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Revert "i2c: designware: defer probe if child GpioInt controllers are not bound"
Date: Fri, 14 Aug 2026 23:19:51 +0200	[thread overview]
Message-ID: <an-GZpgfiPJj2JsV@zenone.zhora.eu> (raw)
In-Reply-To: <20260814100719.9548-1-hardikprakash.official@gmail.com>

Hi Hardik,

On Fri, Aug 14, 2026 at 03:37:19PM +0530, Hardik Prakash wrote:
> This reverts commit 0a4bb2abc3e56d7be6e69b050c88ba52c87e22bf.
> 
> The reverted commit causes a regression on ThinkPad T14s Gen 4 (AMD):
> the touchpad's I2C controller fails with lost arbitration errors,
> because it delays i2c-designware's probe by roughly 500ms, which
> shifts the touchpad's first HID descriptor fetch into a window where
> the platform's embedded controller is still acting as a secondary I2C
> bus master. Debug tracing confirms the GpioInt dependency check itself
> behaves correctly (it defers appropriately and confirms the GPIO
> controller is bound); the arbitration failure happens roughly a
> second after the check passes, when i2c_hid_acpi's own probe attempts
> its first transaction.
> 
> The original fix is still needed for the Lenovo Yoga 7 14AGP11
> touchscreen race the commit addressed, but a corrected version will
> be resubmitted once the EC bus-mastering interaction is understood
> and handled properly, rather than reintroducing a different
> regression on more widely-used ThinkPad hardware in the meantime.
> 
> Reported-by: Thorsten Leemhuis <linux@leemhuis.info>
> Closes: https://lore.kernel.org/all/b4a4eadb-282f-464c-843a-19d415a34d0c@leemhuis.info/
> Signed-off-by: Hardik Prakash <hardikprakash.official@gmail.com>

merged to i2c/i2c-2.

Thanks,
Andi

      parent reply	other threads:[~2026-08-14 21:19 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-14 10:07 Hardik Prakash
2026-08-14 10:49 ` Thorsten Leemhuis
2026-08-14 14:55 ` Mario Limonciello
2026-08-14 21:19 ` Andi Shyti [this message]

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