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From:   Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
Date:   Thu, 10 Oct 2019 15:02:13 +0530
Message-ID: <CAHO=5PFSTomeNm4vAKyPmRZXNPBKGT4ck3mB8uOY395uwuVdNg@mail.gmail.com>
Subject: Re: [PATCH v2 1/1] i2c: iproc: Add i2c repeated start capability
To:     Ray Jui <rjui@broadcom.com>, Scott Branden <sbranden@broadcom.com>,
        BCM Kernel Feedback <bcm-kernel-feedback-list@broadcom.com>,
        Wolfram Sang <wsa@the-dreams.de>,
        Michael Cheng <ccheng@broadcom.com>,
        Shreesha Rajashekar <shreesha.rajashekar@broadcom.com>,
        Lori Hikichi <lori.hikichi@broadcom.com>,
        linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Cc:     Icarus Chau <icarus.chau@broadcom.com>,
        Ray Jui <ray.jui@broadcom.com>,
        Shivaraj Shetty <sshetty1@broadcom.com>
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Hi Wolfram,

Did you get a chance to review this patch.

Best regards,
Rayagonda


On Mon, Sep 30, 2019 at 12:19 PM Rayagonda Kokatanur
<rayagonda.kokatanur@broadcom.com> wrote:
>
> From: Lori Hikichi <lori.hikichi@broadcom.com>
>
> Enable handling of i2c repeated start. The current code
> handles a multi msg i2c transfer as separate i2c bus
> transactions. This change will now handle this case
> using the i2c repeated start protocol. The number of msgs
> in a transfer is limited to two, and must be a write
> followed by a read.
>
> Signed-off-by: Lori Hikichi <lori.hikichi@broadcom.com>
> Signed-off-by: Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
> Signed-off-by: Icarus Chau <icarus.chau@broadcom.com>
> Signed-off-by: Ray Jui <ray.jui@broadcom.com>
> Signed-off-by: Shivaraj Shetty <sshetty1@broadcom.com>
> ---
> changes from v1:
>  - Address following review comments from Wolfarm Sang,
>    Use i2c_8bit_addr_from_msg() api instead of decoding i2c_msg struct and
>    remove check against number of i2c message as it will be taken care
>    by core using quirks flags.
>
>  drivers/i2c/busses/i2c-bcm-iproc.c | 63 ++++++++++++++++++++++++++++++--------
>  1 file changed, 50 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c b/drivers/i2c/busses/i2c-bcm-iproc.c
> index d7fd76b..e478db7 100644
> --- a/drivers/i2c/busses/i2c-bcm-iproc.c
> +++ b/drivers/i2c/busses/i2c-bcm-iproc.c
> @@ -81,6 +81,7 @@
>  #define M_CMD_PROTOCOL_MASK          0xf
>  #define M_CMD_PROTOCOL_BLK_WR        0x7
>  #define M_CMD_PROTOCOL_BLK_RD        0x8
> +#define M_CMD_PROTOCOL_PROCESS       0xa
>  #define M_CMD_PEC_SHIFT              8
>  #define M_CMD_RD_CNT_SHIFT           0
>  #define M_CMD_RD_CNT_MASK            0xff
> @@ -675,13 +676,20 @@ static int bcm_iproc_i2c_xfer_wait(struct bcm_iproc_i2c_dev *iproc_i2c,
>         return 0;
>  }
>
> -static int bcm_iproc_i2c_xfer_single_msg(struct bcm_iproc_i2c_dev *iproc_i2c,
> -                                        struct i2c_msg *msg)
> +/*
> + * If 'process_call' is true, then this is a multi-msg transfer that requires
> + * a repeated start between the messages.
> + * More specifically, it must be a write (reg) followed by a read (data).
> + * The i2c quirks are set to enforce this rule.
> + */
> +static int bcm_iproc_i2c_xfer_internal(struct bcm_iproc_i2c_dev *iproc_i2c,
> +                                       struct i2c_msg *msgs, bool process_call)
>  {
>         int i;
>         u8 addr;
>         u32 val, tmp, val_intr_en;
>         unsigned int tx_bytes;
> +       struct i2c_msg *msg = &msgs[0];
>
>         /* check if bus is busy */
>         if (!!(iproc_i2c_rd_reg(iproc_i2c,
> @@ -707,14 +715,29 @@ static int bcm_iproc_i2c_xfer_single_msg(struct bcm_iproc_i2c_dev *iproc_i2c,
>                         val = msg->buf[i];
>
>                         /* mark the last byte */
> -                       if (i == msg->len - 1)
> -                               val |= BIT(M_TX_WR_STATUS_SHIFT);
> +                       if (!process_call && (i == msg->len - 1))
> +                               val |= 1 << M_TX_WR_STATUS_SHIFT;
>
>                         iproc_i2c_wr_reg(iproc_i2c, M_TX_OFFSET, val);
>                 }
>                 iproc_i2c->tx_bytes = tx_bytes;
>         }
>
> +       /* Process the read message if this is process call */
> +       if (process_call) {
> +               msg++;
> +               iproc_i2c->msg = msg;  /* point to second msg */
> +
> +               /*
> +                * The last byte to be sent out should be a slave
> +                * address with read operation
> +                */
> +               addr = i2c_8bit_addr_from_msg(msg);
> +               /* mark it the last byte out */
> +               val = addr | (1 << M_TX_WR_STATUS_SHIFT);
> +               iproc_i2c_wr_reg(iproc_i2c, M_TX_OFFSET, val);
> +       }
> +
>         /* mark as incomplete before starting the transaction */
>         if (iproc_i2c->irq)
>                 reinit_completion(&iproc_i2c->done);
> @@ -733,7 +756,7 @@ static int bcm_iproc_i2c_xfer_single_msg(struct bcm_iproc_i2c_dev *iproc_i2c,
>          * underrun interrupt, which will be triggerred when the TX FIFO is
>          * empty. When that happens we can then pump more data into the FIFO
>          */
> -       if (!(msg->flags & I2C_M_RD) &&
> +       if (!process_call && !(msg->flags & I2C_M_RD) &&
>             msg->len > iproc_i2c->tx_bytes)
>                 val_intr_en |= BIT(IE_M_TX_UNDERRUN_SHIFT);
>
> @@ -743,6 +766,8 @@ static int bcm_iproc_i2c_xfer_single_msg(struct bcm_iproc_i2c_dev *iproc_i2c,
>          */
>         val = BIT(M_CMD_START_BUSY_SHIFT);
>         if (msg->flags & I2C_M_RD) {
> +               u32 protocol;
> +
>                 iproc_i2c->rx_bytes = 0;
>                 if (msg->len > M_RX_FIFO_MAX_THLD_VALUE)
>                         iproc_i2c->thld_bytes = M_RX_FIFO_THLD_VALUE;
> @@ -758,7 +783,10 @@ static int bcm_iproc_i2c_xfer_single_msg(struct bcm_iproc_i2c_dev *iproc_i2c,
>                 /* enable the RX threshold interrupt */
>                 val_intr_en |= BIT(IE_M_RX_THLD_SHIFT);
>
> -               val |= (M_CMD_PROTOCOL_BLK_RD << M_CMD_PROTOCOL_SHIFT) |
> +               protocol = process_call ?
> +                               M_CMD_PROTOCOL_PROCESS : M_CMD_PROTOCOL_BLK_RD;
> +
> +               val |= (protocol << M_CMD_PROTOCOL_SHIFT) |
>                        (msg->len << M_CMD_RD_CNT_SHIFT);
>         } else {
>                 val |= (M_CMD_PROTOCOL_BLK_WR << M_CMD_PROTOCOL_SHIFT);
> @@ -774,17 +802,24 @@ static int bcm_iproc_i2c_xfer(struct i2c_adapter *adapter,
>                               struct i2c_msg msgs[], int num)
>  {
>         struct bcm_iproc_i2c_dev *iproc_i2c = i2c_get_adapdata(adapter);
> -       int ret, i;
> +       bool process_call = false;
> +       int ret;
>
> -       /* go through all messages */
> -       for (i = 0; i < num; i++) {
> -               ret = bcm_iproc_i2c_xfer_single_msg(iproc_i2c, &msgs[i]);
> -               if (ret) {
> -                       dev_dbg(iproc_i2c->device, "xfer failed\n");
> -                       return ret;
> +       if (num == 2) {
> +               /* Repeated start, use process call */
> +               process_call = true;
> +               if (msgs[1].flags & I2C_M_NOSTART) {
> +                       dev_err(iproc_i2c->device, "Invalid repeated start\n");
> +                       return -EOPNOTSUPP;
>                 }
>         }
>
> +       ret = bcm_iproc_i2c_xfer_internal(iproc_i2c, msgs, process_call);
> +       if (ret) {
> +               dev_dbg(iproc_i2c->device, "xfer failed\n");
> +               return ret;
> +       }
> +
>         return num;
>  }
>
> @@ -806,6 +841,8 @@ static uint32_t bcm_iproc_i2c_functionality(struct i2c_adapter *adap)
>  };
>
>  static struct i2c_adapter_quirks bcm_iproc_i2c_quirks = {
> +       .flags = I2C_AQ_COMB_WRITE_THEN_READ,
> +       .max_comb_1st_msg_len = M_TX_RX_FIFO_SIZE,
>         .max_read_len = M_RX_MAX_READ_LEN,
>  };
>
> --
> 1.9.1
>