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ORIGINATING; auth=pass smtp.auth=pza@pengutronix.de smtp.mailfrom=p.zabel@pengutronix.de ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=pengutronix.de; s=20260414; t=1793006678; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ljkgYSSqUVNlSRlN0OwHYowt9zrJ7++/rJlr53nk23A=; b=cIe9UxPpXv33lQVGBG68UzyFxxXr8dA8gva5s11zaTlNSRy3gUU1xsCtZ5388j+YqYjCoD pdJAxKShRf7+1C84Yc+VFu/LOc9ApTHVgWj1TjmWwPjtrIFWnjf8IubKB3sOCyDg/6XoIS h5ffookUiC1fVJMyAtum+B0kbAQOuFHKbqPINkDiTmwdHbAnADa2PlpkPBsPVWkD0SGngT uM6gQsI/g0CbtWk2e8dZd5O13pQlKKthKxyzGd7SUf84dcHlIXC7BYjr3Y+3iV7W/zEe6Z LX02H5R/IqQONjGm9zGiyFPL/y2JgtkG3v2bwPEvARrYzwfNaet+JifxV9kzvQ== Message-ID: <0ecf3ca284f6e9301d2c44a9df8fddf27aebab58.camel@pengutronix.de> Subject: Re: [PATCH v4 1/2] reset: core: Serialize concurrent deassert/reset of shared resets From: Philipp Zabel To: shengjiu.wang@oss.nxp.com, krzk@kernel.org, hansg@kernel.org, linux-kernel@vger.kernel.org, broonie@kernel.org, alvin.sipraga@analog.com Date: Mon, 26 Oct 2026 10:24:38 +0100 In-Reply-To: <20261023071609.3795354-2-shengjiu.wang@oss.nxp.com> References: <20261023071609.3795354-1-shengjiu.wang@oss.nxp.com> <20261023071609.3795354-2-shengjiu.wang@oss.nxp.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2-0+deb13u1 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 On Fr, 2026-10-23 at 15:16 +0800, shengjiu.wang@oss.nxp.com wrote: > From: Shengjiu Wang >=20 > Add a reset_controller_dev::can_sleep flag that a provider sets when its > reset ops may sleep. When it is set, serialize the shared refcount update > and the hardware op in reset_control_reset(), reset_control_deassert() an= d > reset_control_assert() under a new per-control mutex, taken inside the SR= CU > read-side critical section. Providers that leave the flag clear keep the > existing lockless path, so callers in atomic context are unaffected. >=20 > reset_control_deassert() and reset_control_reset() are documented to > guarantee that the reset line has been deasserted, respectively that a > reset pulse has been issued, by the time they return. >=20 > For a shared reset only the first caller runs the hardware op; the other > callers just bump the refcount and return. When the op can sleep this > breaks the guarantee: a second caller can observe the bumped refcount and > return before the first caller's op has finished, and then touch hardware > that is still in reset. A reset_control_assert() racing a concurrent > reset_control_deassert() can likewise interleave the two sleeping ops and > leave the line asserted while the refcount says it is deasserted. >=20 > Suggested-by: Philipp Zabel > Signed-off-by: Shengjiu Wang > Link: https://lore.kernel.org/all/aszDZlJ0KahNwgZO@analog.com/ Reviewed-by: Philipp Zabel regards Philipp