From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794064878; b=Qop10RhQTpQ5+/GYuyiSAxOaVDrV33Pj9Jl6uq26qWIzyCCCANX7rcuLMkkeWdfGKZS5 Ed7/QkS0N+rAoKxOwTsc1xtIkSoECKF3uSQvw7DwQXPY/u27O1bDNYuqEiRWxoowHfKDk w24xu4b8dmblkWgaiTiKzMRyEAbabW94VIjwkMrMgvqTUIi7HqmOfNMS3iHhFidzTFYPi mR+iZ1JoL+/JrF30l2H+irBeonZ9+ddXmNA9z6fjUiwszS6QD2ydX89fXJOoYRYyBQyNg RRbcGfnRv0FATXNiE5rj3sV535GOL61+e8ejqyDsXKohbPl2s7eZLKAvXxhS2/owbCA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794064878; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=cwqWYRasLFeEJOljOZVtXpETlhvtZsTvPgQxUBj8Bps=; b=pHahiNNT1WogRcF/fuWIcFPbueA2KgVGFOEAirGSdwiTB8Dp070JawCY+vu3/DNsfP20 hAU4yTZW/ut2uEW2CHF1y330XrCDxd9CHfe88IQBf6V+RSTOspsBtEBhmmE2ER4cWPeGo 0yNBcPw7DGSw60sVF6JXFH/B+AGIHLX1JDfNQye1/eWFnCRQgnu+oJLx4TwZBNMRacx52 6xhfcXUpOj740d/V3FxxlYdVSfl6i3co+xQ/LNLnS5oknWsJwdR6DLlx2Ipy5lAZFoFEN 8xpiuU1nGdyH4o10iWv5n5Qwx19W4Iz1M2wUD4R/Sxr+14CCHUemcf+1qswXhQG+fGQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=NX0YCOXr; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5344F606A9DB; Sat, 7 Nov 2026 15:21:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=NX0YCOXr Received: by smtp.kernel.org (Postfix) with ESMTPSA id F391A1F0089F; Sat, 7 Nov 2026 15:21:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794064878; bh=cwqWYRasLFeEJOljOZVtXpETlhvtZsTvPgQxUBj8Bps=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=NX0YCOXrTETF2p9EIwyzalP6rV2+J00Y8NN+S8rVp7Qesm0Dw0cb3uoIs2Ji2jReq yKkCTB7FhsPV61tto2WLvle7O/EdLOg2j8ozWsGm7F/ih/r/XvT/nd+4eOkKrdEIl0 XL2P/WdFsfmt7tZFrbdaSun5ANO7wz/ViaAWicFw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable@kernel.org, Ferry Toth , Andy Shevchenko , Sasha Levin Subject: [PATCH 7.3 0754/1257] Revert "serial: 8250_port: Drop duplicate NULL check" Date: Sat, 7 Nov 2026 08:50:50 -0500 Message-ID: <20261107135000.114051946@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261107134939.434104957@linuxfoundation.org> References: <20261107134939.434104957@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ferry Toth [ Upstream commit 6ae994d513a6ace5462137e1025a4e7086b87348 ] This reverts commit 7885af04df6e4efd72910200c1bfc079d61202e4. Commit 7885af04df6e ("serial: 8250_port: Drop duplicate NULL check") added `up->dma = NULL;` to serial8250_release_dma(), with the stated intent of making sure DMA would not be used again after release. However, up->dma is assigned once at probe time. serial8250_do_startup() only calls serial8250_request_dma() when up->dma is non-NULL, so after the first close the pointer stays NULL and DMA is never re-acquired. On Intel Tangier (Edison) with HSU DMA this causes a regression: the first port open uses TX DMA, the second and later opens transmit in PIO mode, producing 64-byte FIFO bursts with ~50us gaps between them. Fixes: 7885af04df6e ("serial: 8250_port: Drop duplicate NULL check") Cc: stable@kernel.org Signed-off-by: Ferry Toth Acked-by: Andy Shevchenko Link: https://patch.msgid.link/20261010193755.187706-2-ftoth@exalondelft.nl Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/8250/8250_port.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index b01baff71f60e..c961b969021ec 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2428,8 +2428,8 @@ void serial8250_do_shutdown(struct uart_port *port) synchronize_irq(port->irq); - serial8250_release_dma(up); - up->dma = NULL; + if (up->dma) + serial8250_release_dma(up); scoped_guard(uart_port_lock_irqsave, port) { if (port->flags & UPF_FOURPORT) { -- 2.53.0