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[91.79.175.49]) by smtp.googlemail.com with ESMTPSA id j73sm35580115pge.13.2019.01.25.11.55.11 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 25 Jan 2019 11:55:16 -0800 (PST) Subject: Re: [PATCH V2 2/4] i2c: tegra: Update I2C transfer using buffer To: Sowjanya Komatineni , thierry.reding@gmail.com, jonathanh@nvidia.com, mkarthik@nvidia.com, smohammed@nvidia.com, talho@nvidia.com Cc: linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org References: <1548363113-25969-1-git-send-email-skomatineni@nvidia.com> <1548363113-25969-2-git-send-email-skomatineni@nvidia.com> From: Dmitry Osipenko Message-ID: <185da588-1080-1589-46b6-5b63dff681eb@gmail.com> Date: Fri, 25 Jan 2019 22:55:07 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <1548363113-25969-2-git-send-email-skomatineni@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 24.01.2019 23:51, Sowjanya Komatineni пишет: > This patch prepares the buffer with the message bytes to be > transmitted along with the packet header information and then > performs i2c transfer in PIO mode. > > Signed-off-by: Sowjanya Komatineni > --- > [V2] : DMA support changes include preparing buffer with message bytes and > and header before sending them through DMA. So splitted the whole > change into 2 seperate patches in this series. > > drivers/i2c/busses/i2c-tegra.c | 97 +++++++++++++++++++++++++++++------------- > 1 file changed, 68 insertions(+), 29 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c > index ef854be4c837..13bce1411ddc 100644 > --- a/drivers/i2c/busses/i2c-tegra.c > +++ b/drivers/i2c/busses/i2c-tegra.c > @@ -117,6 +117,9 @@ > #define I2C_MST_FIFO_STATUS_TX_MASK 0xff0000 > #define I2C_MST_FIFO_STATUS_TX_SHIFT 16 > > +/* Packet header size in bytes */ > +#define I2C_PACKET_HEADER_SIZE 12 > + > /* > * msg_end_type: The bus control which need to be send at end of transfer. > * @MSG_END_STOP: Send stop pulse at end of transfer. > @@ -677,35 +680,69 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id) > return IRQ_HANDLED; > } > > +static int tegra_i2c_start_pio_xfer(struct tegra_i2c_dev *i2c_dev) > +{ > + u32 *buffer = (u32 *)i2c_dev->msg_buf; > + unsigned long flags; > + u32 int_mask; > + > + spin_lock_irqsave(&i2c_dev->xfer_lock, flags); > + > + int_mask = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST; > + tegra_i2c_unmask_irq(i2c_dev, int_mask); > + > + i2c_writel(i2c_dev, *(buffer++), I2C_TX_FIFO); > + i2c_writel(i2c_dev, *(buffer++), I2C_TX_FIFO); > + i2c_writel(i2c_dev, *(buffer++), I2C_TX_FIFO); > + > + i2c_dev->msg_buf = (u8 *) buffer; > + > + if (!i2c_dev->msg_read) > + tegra_i2c_fill_tx_fifo(i2c_dev); > + > + if (i2c_dev->hw->has_per_pkt_xfer_complete_irq) > + int_mask |= I2C_INT_PACKET_XFER_COMPLETE; > + if (i2c_dev->msg_read) > + int_mask |= I2C_INT_RX_FIFO_DATA_REQ; > + else if (i2c_dev->msg_buf_remaining) > + int_mask |= I2C_INT_TX_FIFO_DATA_REQ; > + > + tegra_i2c_unmask_irq(i2c_dev, int_mask); > + spin_unlock_irqrestore(&i2c_dev->xfer_lock, flags); > + dev_dbg(i2c_dev->dev, "unmasked irq: %02x\n", > + i2c_readl(i2c_dev, I2C_INT_MASK)); > + > + return 0; > +} > + > static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev, > struct i2c_msg *msg, enum msg_end_type end_state) > { > u32 packet_header; > u32 int_mask; > unsigned long time_left; > - unsigned long flags; > + u32 *buffer; > + int ret = 0; > + > + buffer = kmalloc(ALIGN(msg->len, BYTES_PER_FIFO_WORD) + > + I2C_PACKET_HEADER_SIZE, GFP_KERNEL); > + if (!buffer) > + return -ENOMEM; Isn't it possible to avoid "buffer" allocation / copying overhead and keep code as-is for the PIO mode? 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