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[188.155.177.222]) by smtp.gmail.com with ESMTPSA id h14sm3068530ejl.118.2021.06.28.01.44.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 28 Jun 2021 01:44:52 -0700 (PDT) Subject: Re: [PATCH v4] serial: samsung: use dma_ops of DMA if attached To: Tamseel Shams , gregkh@linuxfoundation.org, jirislaby@kernel.org Cc: linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, alim.akhtar@samsung.com, ajaykumar.rs@samsung.com, robin.murphy@arm.com References: <20210625075114.71155-1-m.shams@samsung.com> From: Krzysztof Kozlowski Message-ID: <3aa88ee4-c662-8069-fb04-90df82038dbe@canonical.com> Date: Mon, 28 Jun 2021 10:44:51 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210625075114.71155-1-m.shams@samsung.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org On 25/06/2021 09:51, Tamseel Shams wrote: > When DMA is used for TX and RX by serial driver, it should > pass the DMA device pointer to DMA API instead of UART device > pointer. DMA device should be used for DMA API because only > the DMA device is aware of how the device connects to the memory. > There might be an extra level of address translation due to a > SMMU attached to the DMA device. When serial device is used for > DMA API, the DMA API will have no clue of the SMMU attached to > the DMA device. > > This patch is necessary to fix the SMMU page faults > which is observed when a DMA(with SMMU enabled) is attached > to UART for transfer. > > Signed-off-by: Tamseel Shams > Signed-off-by: Ajay Kumar > --- > Changes since v1: > 1. Rebased the patch on "tty-next" branch of TTY driver tree > > Changes since v2: > 1. Updated the commit message. > 2. Changed the comment description > > Changes since v3: > 1. Removed the null pointer check for "dma", "dma->tx_chan" and > "dma->rx_chan" and instead sending DMA device pointer while calling > DMA API. > > drivers/tty/serial/samsung_tty.c | 32 ++++++++++++++++---------------- > 1 file changed, 16 insertions(+), 16 deletions(-) > > diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c > index 9fbc61151c2e..fa30aa20a13f 100644 > --- a/drivers/tty/serial/samsung_tty.c > +++ b/drivers/tty/serial/samsung_tty.c > @@ -305,7 +305,7 @@ static void s3c24xx_serial_stop_tx(struct uart_port *port) > dmaengine_pause(dma->tx_chan); > dmaengine_tx_status(dma->tx_chan, dma->tx_cookie, &state); > dmaengine_terminate_all(dma->tx_chan); > - dma_sync_single_for_cpu(ourport->port.dev, > + dma_sync_single_for_cpu(dma->tx_chan->device->dev, > dma->tx_transfer_addr, dma->tx_size, DMA_TO_DEVICE); > async_tx_ack(dma->tx_desc); > count = dma->tx_bytes_requested - state.residue; > @@ -338,8 +338,8 @@ static void s3c24xx_serial_tx_dma_complete(void *args) > count = dma->tx_bytes_requested - state.residue; > async_tx_ack(dma->tx_desc); > > - dma_sync_single_for_cpu(ourport->port.dev, dma->tx_transfer_addr, > - dma->tx_size, DMA_TO_DEVICE); > + dma_sync_single_for_cpu(dma->tx_chan->device->dev, > + dma->tx_transfer_addr, dma->tx_size, DMA_TO_DEVICE); Looks like alignment is broken here. However even if the line was not aligned before, please fix it up now - align the arguments like checkpatch suggests. This applies to other places as well. Thanks. Best regards, Krzysztof