From patchwork Wed Nov 23 08:27:36 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jiri Slaby X-Patchwork-Id: 13053249 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6E16CC4332F for ; Wed, 23 Nov 2022 08:29:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=E3c1KFv5vnuOrR4sdAGP4tbZ8PqDI/wo1+e4dHaxtC4=; b=A/BdnPcnAiEugG xSZbvY98YjpqX1TnqLlCoAGTRlSIUjiJ78qZKkNdV22AEaKqkp1xctLKzqxGzaTZ/RdsPXfqtnKUI TUwtJYXtEiBHRFht3ZQxAH2LxTU83G+7LfOwGEAxeowQkUEotwlcBx2Q6pgoqJwzg7eyyuVq0nsJU uScZoJMvvqqGIVZX72Sf1vhY9nTZCP5ZPu24kSlyTDf2MB0Ul2Lxrqyjcc6YnlthICngsLcaEVpBq EI82jJC8qs9c2WD645ND3kxAWlecuy7mEk+DCA2jwpMsjrgzWHRGAh9TioElsPDjB8UUQYN/QKMWa zeB7D7x0n+0u+PukNEUw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oxl75-00FWii-Df; Wed, 23 Nov 2022 08:28:11 +0000 Received: from ams.source.kernel.org ([2604:1380:4601:e00::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oxl6g-00FWYW-QP for linux-arm-kernel@lists.infradead.org; Wed, 23 Nov 2022 08:27:48 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 2AABBB81EEA; Wed, 23 Nov 2022 08:27:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 962ACC433D7; Wed, 23 Nov 2022 08:27:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669192063; bh=+Gj9VY8s8NivuczNkGfzHn17+4LSQEt5i0IRoGeWmyc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=leqf/6jLvGhj6Vo0mGKQlru4xbl5WhJElvBN0FT2SCaHSpIXBm1QJnND/RwqkHniX UN254aoLDitmLzn65QxcdHj5EBSIToN0XmuAPy72V3O6M8nXwOg45TEhQHsQma3LDd GTE2G4vT9X0qwAtea+cM0OiforWe7iGdwzNqS5xZXtJO/Dbx0HGDC57JT3GDMKt4HF 8WgR4p2Gg2XFcX0idYJ13zhZSXSLALftFKnnxgIdKBOfHTHTTvpBEphEut479s0xbn Iq8ZGSNi+3TnA6vPAzeVDQ9cAI0QjRvcei38ZlEpOlB/o/JckE8hjRruwIUR/vGnNr 7AnoR5oizfUmQ== From: "Jiri Slaby (SUSE)" To: gregkh@linuxfoundation.org Subject: [PATCH 2/2] serial: atmel: don't stop the transmitter when doing PIO Date: Wed, 23 Nov 2022 09:27:36 +0100 Message-Id: <20221123082736.24566-2-jirislaby@kernel.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221123082736.24566-1-jirislaby@kernel.org> References: <20221123082736.24566-1-jirislaby@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221123_002747_192549_B14E0ABE X-CRM114-Status: GOOD ( 18.24 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexandre Belloni , Richard Genoud , linux-kernel@vger.kernel.org, Michael Walle , linux-serial@vger.kernel.org, "Jiri Slaby \(SUSE\)" , Claudiu Beznea , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Writing ATMEL_US_TXDIS to ATMEL_US_CR makes the transmitter NOT to send the just queued character. This means when the character is last and uart calls ops->stop_tx(), the character is not sent at all. The usart datasheet is not much specific on this, it just says the transmitter is stopped. But apparently, the character is dropped. So we should stop the transmitter only for DMA and PDC transfers to not send any more characters. For PIO, this is unexpected and deviates from other drivers. In particular, the below referenced commit broke TX as it added a call to ->stop_tx() after the very last character written to the transmitter. So fix this by limiting the write of ATMEL_US_TXDIS to DMA transfers only. Even there, I don't know if it is correctly implemented. Are all the queued characters sent once ->start_tx() is called? Anyone tested flow control -- be it hard (RTSCTS) or the soft (XOFF/XON) one? Fixes: 2d141e683e9a ("tty: serial: use uart_port_tx() helper") Cc: Richard Genoud Cc: Nicolas Ferre Cc: Alexandre Belloni Cc: Claudiu Beznea Cc: linux-arm-kernel@lists.infradead.org Reported-by: Michael Walle Signed-off-by: Jiri Slaby (SUSE) Tested-by: Michael Walle Acked-by: Richard Genoud --- drivers/tty/serial/atmel_serial.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c index 65f63dccfd72..f1c06e12efa0 100644 --- a/drivers/tty/serial/atmel_serial.c +++ b/drivers/tty/serial/atmel_serial.c @@ -553,19 +553,22 @@ static void atmel_stop_tx(struct uart_port *port) { struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); bool is_pdc = atmel_use_pdc_tx(port); + bool is_dma = is_pdc || atmel_use_dma_tx(port); if (is_pdc) { /* disable PDC transmit */ atmel_uart_writel(port, ATMEL_PDC_PTCR, ATMEL_PDC_TXTDIS); } - /* - * Disable the transmitter. - * This is mandatory when DMA is used, otherwise the DMA buffer - * is fully transmitted. - */ - atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXDIS); - atmel_port->tx_stopped = true; + if (is_dma) { + /* + * Disable the transmitter. + * This is mandatory when DMA is used, otherwise the DMA buffer + * is fully transmitted. + */ + atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXDIS); + atmel_port->tx_stopped = true; + } /* Disable interrupts */ atmel_uart_writel(port, ATMEL_US_IDR, atmel_port->tx_done_mask); @@ -601,9 +604,11 @@ static void atmel_start_tx(struct uart_port *port) /* Enable interrupts */ atmel_uart_writel(port, ATMEL_US_IER, atmel_port->tx_done_mask); - /* re-enable the transmitter */ - atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN); - atmel_port->tx_stopped = false; + if (is_dma) { + /* re-enable the transmitter */ + atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN); + atmel_port->tx_stopped = false; + } } /*