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Subject: Re: [PATCH v5 3/5] i2c: mediatek: Add arb clock in i2c driver
From:   Qii Wang <qii.wang@mediatek.com>
To:     Nicolas Boichat <drinkcat@chromium.org>
CC:     <wsa@the-dreams.de>, <linux-i2c@vger.kernel.org>,
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        Leilk Liu <leilk.liu@mediatek.com>,
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        Rob Herring <robh@kernel.org>
Date:   Thu, 7 Mar 2019 12:57:57 +0800
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On Wed, 2019-03-06 at 18:49 +0800, Nicolas Boichat wrote:
> One thing I missed from Matthias' comment on v4:
> https://patchwork.kernel.org/patch/10822083/
> 
> On Wed, Mar 6, 2019 at 6:44 PM Nicolas Boichat <drinkcat@chromium.org> wrote:
> >
> > On Tue, Feb 26, 2019 at 9:11 PM Qii Wang <qii.wang@mediatek.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@mediatek.com>
> >
> > Reviewed-by: Nicolas Boichat <drinkcat@chromium.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);
> 
> Is it ok to set I2C_ARB_LOST on _all_ SoC that this driver supports?
> If so, please at least say so in the commit message.
> 

Yes, old and new SoC have the I2C_ARB_LOST bit, but there was no need
for multi-master before, so we didn't set it up specifically, I have
test the patch on the old SoCs. I will add a note in the commit message.

> > >
> > >         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
> > >