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Date:   Wed, 6 Mar 2019 18:44:05 +0800
From:   Nicolas Boichat <drinkcat@...omium.org>
To:     Qii Wang <qii.wang@...iatek.com>
Cc:     wsa@...-dreams.de, linux-i2c@...r.kernel.org,
        devicetree@...r.kernel.org,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        srv_heupstream <srv_heupstream@...iatek.com>,
        Leilk Liu <leilk.liu@...iatek.com>, xinping.qian@...iatek.com,
        liguo.zhang@...iatek.com, Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v5 3/5] i2c: mediatek: Add arb clock in i2c driver

On Tue, Feb 26, 2019 at 9:11 PM Qii Wang <qii.wang@...iatek.com> wrote:
>
> When two i2c controllers are internally connected to the same
> GPIO pins, the arb clock is needed to ensure that the waveforms
> do not interfere with each other.
>
> Signed-off-by: Qii Wang <qii.wang@...iatek.com>

Reviewed-by: Nicolas Boichat <drinkcat@...omium.org>

> ---
>  drivers/i2c/busses/i2c-mt65xx.c |   25 ++++++++++++++++++++++---
>  1 file changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
> index 428ac99..14d6b38 100644
> --- a/drivers/i2c/busses/i2c-mt65xx.c
> +++ b/drivers/i2c/busses/i2c-mt65xx.c
> @@ -35,6 +35,7 @@
>  #include <linux/slab.h>
>
>  #define I2C_RS_TRANSFER                        (1 << 4)
> +#define I2C_ARB_LOST                   (1 << 3)
>  #define I2C_HS_NACKERR                 (1 << 2)
>  #define I2C_ACKERR                     (1 << 1)
>  #define I2C_TRANSAC_COMP               (1 << 0)
> @@ -181,6 +182,7 @@ struct mtk_i2c {
>         struct clk *clk_main;           /* main clock for i2c bus */
>         struct clk *clk_dma;            /* DMA clock for i2c via DMA */
>         struct clk *clk_pmic;           /* PMIC clock for i2c from PMIC */
> +       struct clk *clk_arb;            /* Arbitrator clock for i2c */
>         bool have_pmic;                 /* can use i2c pins from PMIC */
>         bool use_push_pull;             /* IO config push-pull mode */
>
> @@ -299,8 +301,18 @@ static int mtk_i2c_clock_enable(struct mtk_i2c *i2c)
>                 if (ret)
>                         goto err_pmic;
>         }
> +
> +       if (i2c->clk_arb) {
> +               ret = clk_prepare_enable(i2c->clk_arb);
> +               if (ret)
> +                       goto err_arb;
> +       }
> +
>         return 0;
>
> +err_arb:
> +       if (i2c->have_pmic)
> +               clk_disable_unprepare(i2c->clk_pmic);
>  err_pmic:
>         clk_disable_unprepare(i2c->clk_main);
>  err_main:
> @@ -311,6 +323,9 @@ static int mtk_i2c_clock_enable(struct mtk_i2c *i2c)
>
>  static void mtk_i2c_clock_disable(struct mtk_i2c *i2c)
>  {
> +       if (i2c->clk_arb)
> +               clk_disable_unprepare(i2c->clk_arb);
> +
>         if (i2c->have_pmic)
>                 clk_disable_unprepare(i2c->clk_pmic);
>
> @@ -519,13 +534,13 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs,
>
>         /* Clear interrupt status */
>         mtk_i2c_writew(i2c, restart_flag | I2C_HS_NACKERR | I2C_ACKERR |
> -              I2C_TRANSAC_COMP, OFFSET_INTR_STAT);
> +                           I2C_ARB_LOST | I2C_TRANSAC_COMP, OFFSET_INTR_STAT);
>
>         mtk_i2c_writew(i2c, I2C_FIFO_ADDR_CLR, OFFSET_FIFO_ADDR_CLR);
>
>         /* Enable interrupt */
>         mtk_i2c_writew(i2c, restart_flag | I2C_HS_NACKERR | I2C_ACKERR |
> -              I2C_TRANSAC_COMP, OFFSET_INTR_MASK);
> +                           I2C_ARB_LOST | I2C_TRANSAC_COMP, OFFSET_INTR_MASK);
>
>         /* Set transfer and transaction len */
>         if (i2c->op == I2C_MASTER_WRRD) {
> @@ -659,7 +674,7 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs,
>
>         /* Clear interrupt mask */
>         mtk_i2c_writew(i2c, ~(restart_flag | I2C_HS_NACKERR | I2C_ACKERR |
> -              I2C_TRANSAC_COMP), OFFSET_INTR_MASK);
> +                           I2C_ARB_LOST | I2C_TRANSAC_COMP), OFFSET_INTR_MASK);
>
>         if (i2c->op == I2C_MASTER_WR) {
>                 dma_unmap_single(i2c->dev, wpaddr,
> @@ -884,6 +899,10 @@ static int mtk_i2c_probe(struct platform_device *pdev)
>                 return PTR_ERR(i2c->clk_dma);
>         }
>
> +       i2c->clk_arb = devm_clk_get(&pdev->dev, "arb");
> +       if (IS_ERR(i2c->clk_arb))
> +               i2c->clk_arb = NULL;
> +
>         clk = i2c->clk_main;
>         if (i2c->have_pmic) {
>                 i2c->clk_pmic = devm_clk_get(&pdev->dev, "pmic");
> --
> 1.7.9.5
>

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