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[3.110.210.194]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1ac1a13652csm17300763c88.17.2026.10.31.05.37.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 31 Oct 2026 05:37:55 -0700 (PDT) From: Samarth Narang To: Greg Kroah-Hartman , Jiri Slaby Cc: Samarth Narang , Russell King , Frank Li , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , linux-serial@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH 0/2] serial: keep the flushed TX buffer mapped until DMA has stopped Date: Sat, 31 Oct 2026 12:37:47 +0000 Message-Id: <20261031123749.3783352-1-samarth.colleges@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20261031005425.3351240-1-samarth.colleges@gmail.com> References: <20261031005425.3351240-1-samarth.colleges@gmail.com> X-Mailing-List: linux-serial@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 This series addresses the DMA buffer lifetime issues in amba-pl011 and fsl_lpuart reported in the parent thread, where flush_buffer() unmaps the TX buffer before the terminated DMA transfer is guaranteed to have stopped accessing it. In fsl_lpuart, the buffer is unmapped even before termination is requested. Since flush_buffer() runs under the port lock and cannot wait for DMA termination, both patches request termination while holding the lock and defer unmapping to a work item that first calls dmaengine_synchronize(). The TX completion callback leaves the cleanup of flushed transfers to this work item, while shutdown, and suspend in the case of fsl_lpuart, waits for the work to finish before releasing the TX DMA state. Both patches have only been compile-tested with arm64 defconfig, the relevant drivers enabled, and W=1, with no new warnings. I do not have access to PL011 or LPUART hardware with DMA support, so testing by someone with suitable hardware would be appreciated. The imx driver also needs a fix for the issue reported in the same thread, but requires a different approach because its TX completion callback unmaps the scatterlist unconditionally. I will send that patch separately. Samarth Narang (2): serial: amba-pl011: keep the flushed TX buffer mapped until DMA stops tty: serial: fsl_lpuart: don't unmap TX buffer before DMA has stopped drivers/tty/serial/amba-pl011.c | 54 +++++++++++++++++++++++++++++++-- drivers/tty/serial/fsl_lpuart.c | 53 ++++++++++++++++++++++++++++---- 2 files changed, 98 insertions(+), 9 deletions(-) base-commit: 36aad21d50d1af3f6954bb0c988257a908202477 -- 2.34.1