From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 66BAF1C29 for ; Wed, 23 Nov 2022 09:36:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D5964C433D6; Wed, 23 Nov 2022 09:36:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1669196176; bh=UyLaojOULzpRt/kL6TcbCknduzXuAjXyN9bB22h18Qw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wZ3qXkedyLmHwNjs26sysxvVs7TdFgwFCNNPl4b2fvafg6aJ9qOJIVl7ZKyi2BN0n jX/KbuKwMdkLNk5glK7Hg7awNk1C4B6T0RWRA9kyWbX/MxJIruD3dfzopIo2genFGS qDsN/wD9g7J6qe83vt2tWmRPiNlMCNlNC4dVFomU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Srikanth Thokala , Aman Kumar , =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= , Andy Shevchenko Subject: [PATCH 5.15 141/181] serial: 8250: Fall back to non-DMA Rx if IIR_RDI occurs Date: Wed, 23 Nov 2022 09:51:44 +0100 Message-Id: <20221123084608.428172565@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221123084602.707860461@linuxfoundation.org> References: <20221123084602.707860461@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Ilpo Järvinen commit a931237cbea256aff13bb403da13a97b2d1605d9 upstream. DW UART sometimes triggers IIR_RDI during DMA Rx when IIR_RX_TIMEOUT should have been triggered instead. Since IIR_RDI has higher priority than IIR_RX_TIMEOUT, this causes the Rx to hang into interrupt loop. The problem seems to occur at least with some combinations of small-sized transfers (I've reproduced the problem on Elkhart Lake PSE UARTs). If there's already an on-going Rx DMA and IIR_RDI triggers, fall graciously back to non-DMA Rx. That is, behave as if IIR_RX_TIMEOUT had occurred. 8250_omap already considers IIR_RDI similar to this change so its nothing unheard of. Fixes: 75df022b5f89 ("serial: 8250_dma: Fix RX handling") Cc: Co-developed-by: Srikanth Thokala Signed-off-by: Srikanth Thokala Co-developed-by: Aman Kumar Signed-off-by: Aman Kumar Signed-off-by: Ilpo Järvinen Reviewed-by: Andy Shevchenko Link: https://lore.kernel.org/r/20221108121952.5497-2-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_port.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1885,6 +1885,10 @@ EXPORT_SYMBOL_GPL(serial8250_modem_statu static bool handle_rx_dma(struct uart_8250_port *up, unsigned int iir) { switch (iir & 0x3f) { + case UART_IIR_RDI: + if (!up->dma->rx_running) + break; + fallthrough; case UART_IIR_RX_TIMEOUT: serial8250_rx_dma_flush(up); fallthrough;