Re: [PATCH 04/12] I2C re-init for every cmd

[jouni.hogander@nokia.com (Högander Jouni)]

"ext shekhar, chandra" <x0044955@ti.com> writes:

> Hi,
>
> Few comments inlined.
>
> Regards,
> Chandra
> ----- Original Message ----- 
> From: ""Högander" Jouni" <jouni.hogander@nokia.com>
> To: "ext Rajendra Nayak" <rnayak@ti.com>
> Cc: <linux-omap@vger.kernel.org>
> Sent: Thursday, September 11, 2008 3:34 PM
> Subject: Re: [PATCH 04/12] I2C re-init for every cmd
>
>
> "ext Rajendra Nayak" <rnayak@ti.com> writes:
>
>> This patch does i2c init/re-init for every transfer
>>
>> Signed-off-by: Rajendra Nayak <rnayak@ti.com>
>> ---
>>  drivers/i2c/busses/i2c-omap.c |    2 ++
>>  1 files changed, 2 insertions(+)
>>
>> Index: linux-omap-2.6/drivers/i2c/busses/i2c-omap.c
>> ===================================================================
>> --- linux-omap-2.6.orig/drivers/i2c/busses/i2c-omap.c 2008-09-01
>> 18:11:28.000000000 +0530
>> +++ linux-omap-2.6/drivers/i2c/busses/i2c-omap.c 2008-09-01 18:11:52.000000000
>> +0530
>> @@ -496,6 +496,8 @@ omap_i2c_xfer(struct i2c_adapter *adap,
>>
>>  omap_i2c_unidle(dev);
>>
>> + omap_i2c_init(dev);
>> +
>>  if ((r = omap_i2c_wait_for_bb(dev)) < 0)
>>  goto out;
>
> This is causing unacceptable delays on i2c transfers. This is because
> occasionally reset loop in init function enters msleep. Is it
> necessary to reset i2c controller after off-mode?
>
> Any opinions on this:
>
> diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> index 3778735..4a27035 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -126,6 +126,14 @@
> /* I2C System Configuration Register (OMAP_I2C_SYSC): */
> #define OMAP_I2C_SYSC_SRST             (1 << 1)        /* Soft Reset */
>
> +struct omap3_i2c_regs {
> +       u16 sysc;
> +       u16 psc;
> +       u16 scll;
> +       u16 sclh;
> +       u16 buf;
> +};
> +
>
>
>
> We can add this as a part of controller structure itself instaed of
> creating a new structure. we will store this
> psc, scll and others as a part of controller and just restore it. That
> way we can do away with  omap3_i2c_save_context every time in clk
> disable.

My patch is neither saving ctx on every clk disable. Just after init.

>
>
>
>
>
> struct omap_i2c_dev {
>        struct device           *dev;
>        void __iomem            *base;          /* virtual */
> @@ -147,6 +155,9 @@ struct omap_i2c_dev {
>        unsigned                b_hw:1;         /* bad h/w fixes */
>        unsigned                idle:1;
>        u16                     iestate;        /* Saved interrupt register */
> +#ifdef CONFIG_ARCH_OMAP34XX
> +       struct omap3_i2c_regs   context;
> +#endif
>
>
>
> I guess this should work for all the platforms. at least for omap2/3
> it should work w/o any hiccups.
> I2C_BUF is the only register which will require cpu check..so while
> restoring we can put that check for 2430/34xx.

Can we use off mode with omap2? Generally, should we build in
save/restore code for other than omap3?

>
>
> };
>
>
>
> static inline void omap_i2c_write_reg(struct omap_i2c_dev *i2c_dev,
> @@ -160,6 +171,26 @@ static inline u16 omap_i2c_read_reg(struct
> omap_i2c_dev *i2c_dev, int reg)
>        return __raw_readw(i2c_dev->base + reg);
> }
>
> +#ifdef CONFIG_ARCH_OMAP34XX
> +void omap3_i2c_save_context(struct omap_i2c_dev *dev)
> +{
> +       dev->context.sysc = omap_i2c_read_reg(dev, OMAP_I2C_SYSC_REG);
> +       dev->context.psc = omap_i2c_read_reg(dev, OMAP_I2C_PSC_REG);
> +       dev->context.scll = omap_i2c_read_reg(dev, OMAP_I2C_SCLL_REG);
> +       dev->context.sclh = omap_i2c_read_reg(dev, OMAP_I2C_SCLH_REG);
> +       dev->context.buf = omap_i2c_read_reg(dev, OMAP_I2C_BUF_REG);
> +}
> +
>
>
> +void omap3_i2c_restore_context(struct omap_i2c_dev *dev)
> +{
> +       omap_i2c_write_reg(dev, OMAP_I2C_SYSC_REG, dev->context.sysc);
> +       omap_i2c_write_reg(dev, OMAP_I2C_PSC_REG, dev->context.psc);
> +       omap_i2c_write_reg(dev, OMAP_I2C_SCLL_REG, dev->context.scll);
> +       omap_i2c_write_reg(dev, OMAP_I2C_SCLH_REG, dev->context.sclh);
> +       omap_i2c_write_reg(dev, OMAP_I2C_BUF_REG, dev->context.buf);
> +}
> +#endif
> +
>
> static int __init omap_i2c_get_clocks(struct omap_i2c_dev *dev)
> {
>        if (cpu_is_omap16xx() || cpu_class_is_omap2()) {
> @@ -210,6 +241,10 @@ static void omap_i2c_unidle(struct omap_i2c_dev *dev)
>                clk_enable(dev->iclk);
>        clk_enable(dev->fclk);
>        dev->idle = 0;
> +
> +       if (cpu_is_omap34xx())
> +               omap3_i2c_restore_context(dev);
> +
>        if (dev->iestate)
>                omap_i2c_write_reg(dev, OMAP_I2C_IE_REG, dev->iestate);
> }
> @@ -344,6 +379,10 @@ static int omap_i2c_init(struct omap_i2c_dev *dev)
>                        OMAP_I2C_IE_ARDY | OMAP_I2C_IE_NACK |
>                        OMAP_I2C_IE_AL)  | ((dev->fifo_size) ?
>                                (OMAP_I2C_IE_RDR | OMAP_I2C_IE_XDR) : 0));
> +
> +       if (cpu_is_omap34xx())
> +               omap3_i2c_save_context(dev);
> +
>
>
>
> this will become redundant as data will be part of controller
> structure.
>
>
>        return 0;
> }
>
> @@ -496,8 +535,6 @@ omap_i2c_xfer(struct i2c_adapter *adap, struct
> i2c_msg msgs[], int num)
>
>        omap_i2c_unidle(dev);
>
> -       omap_i2c_init(dev);
> -
>
>
> instead of calling restore from clk_enable we can replace
> omap_i2c_init by omap3_i2c_restore_context. that way clock enable code
> will be clean.

Well, I though unidle could be ok as ie reg is already restored there?

>
>
>
>        if ((r = omap_i2c_wait_for_bb(dev)) < 0)
>                goto out;
>
> -- 
> Jouni Högander
>
> --
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>
>

-- 
Jouni Högander

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