linux-kernel - Re: [PATCH v2 5/6] i2c: Add Actions Semi OWL family S900 I2C driver

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Message-ID: <20180630124400.GB16775@Mani-XPS-13-9360>
Date:   Sat, 30 Jun 2018 18:14:00 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Wolfram Sang <wsa@...-dreams.de>, Rob Herring <robh+dt@...nel.org>,
        Andreas Färber <afaerber@...e.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        刘炜 <liuwei@...ions-semi.com>,
        mp-cs@...ions-semi.com, 96boards@...obotics.com,
        devicetree <devicetree@...r.kernel.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        amit.kucheria@...aro.org,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        hzhang@...obotics.com, bdong@...obotics.com,
        Mani Sadhasivam <manivannanece23@...il.com>,
        Thomas Liau <thomas.liau@...ions-semi.com>,
        jeff.chen@...ions-semi.com
Subject: Re: [PATCH v2 5/6] i2c: Add Actions Semi OWL family S900 I2C driver

Hi Andy,

On Sat, Jun 30, 2018 at 03:14:37PM +0300, Andy Shevchenko wrote:
> On Thu, Jun 28, 2018 at 9:10 PM, Manivannan Sadhasivam
> <manivannan.sadhasivam@...aro.org> wrote:
> > Add Actions Semi OWL family S900 I2C driver.
> 
> > +#include <linux/clk.h>
> > +#include <linux/delay.h>
> > +#include <linux/i2c.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/module.h>
> > +#include <linux/of_device.h>
> 
> > +#include <linux/io.h>
> 
> Perhaps keep in order?
> 

Fixed in next revision.

> > +#define OWL_I2C_DEFAULT_SPEED  100000
> > +#define OWL_I2C_MAX_SPEED      400000
> 
> ..._SPEED -> ..._SPEED_HZ ?
> 
> DEFAULT -> DEF ?
>

Okay.

> > +static int owl_i2c_reset(struct owl_i2c_dev *i2c_dev)
> > +{
> > +       unsigned int val, timeout = 0;
> > +
> > +       owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
> > +                               OWL_I2C_CTL_EN, false);
> 
> > +       mdelay(1);
> 
> 1 ms keeping CPU busy for nothing. Perhaps usleep_range() / msleep()?
> Is it called in atomic context?
> 

I have removed reset function from the interrupt handler and gave the
justification to my reply to Peter's review.

> > +       owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
> > +                               OWL_I2C_CTL_EN, true);
> > +
> > +       /* Reset FIFO */
> > +       owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_FIFOCTL,
> > +                               OWL_I2C_FIFOCTL_RFR | OWL_I2C_FIFOCTL_TFR,
> > +                               true);
> > +
> > +       /* Wait 50ms for FIFO reset complete */
> > +       do {
> > +               val = readl(i2c_dev->base + OWL_I2C_REG_FIFOCTL);
> > +               if (!(val & (OWL_I2C_FIFOCTL_RFR | OWL_I2C_FIFOCTL_TFR)))
> > +                       break;
> 
> > +               mdelay(1);
> 
> Ditto.
> 

Same as above.

> > +       } while (timeout++ < OWL_I2C_MAX_RETRIES);
> 
> OK, I see you call it from IRQ context. 50ms for IRQ handler is
> inappropriate. (1ms either, but at least not so drastically).
> 

Same as above.

> > +}
> 
> > +static irqreturn_t owl_i2c_interrupt(int irq, void *_dev)
> > +{
> 
> > +       stat = readl(i2c_dev->base + OWL_I2C_REG_STAT);
> > +       if (stat & OWL_I2C_STAT_BEB) {
> > +               dev_dbg(&i2c_dev->adap.dev, "bus error");
> 
> > +               owl_i2c_reset(i2c_dev);
> 
> This is questionable to be here (looking at so loong delays in it).
> 

Same as above.

> > +               goto stop;
> > +       }
> 
> > +       return IRQ_HANDLED;
> > +}
> 
> > +static int owl_i2c_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> > +                               int num)
> > +{
> 
> > +       int ret = 0, idx;
> 
> Redundant assignment.
> 

No. Actually the return path will be fixed in next iteration. Please
see my reply to Peter's review for explanation.

> > +       ret = owl_i2c_hw_init(i2c_dev);
> > +       if (ret)
> > +               return ret;
> 
> > +}
> 
> > +static const struct i2c_algorithm owl_i2c_algorithm = {
> > +       .master_xfer    = owl_i2c_master_xfer,
> 
> > +       .functionality  = owl_i2c_func
> 
> Slightly better to keep comma at the end
> 

Okay.

> > +};
> > +
> > +static const struct i2c_adapter_quirks owl_i2c_quirks = {
> > +       .flags          = I2C_AQ_COMB | I2C_AQ_COMB_WRITE_FIRST,
> > +       .max_read_len   = 240,
> > +       .max_write_len  = 240,
> > +       .max_comb_1st_msg_len = 6,
> > +       .max_comb_2nd_msg_len = 240
> 
> Ditto.
> 

Okay.

Thanks,
Mani

> > +};
> 
> -- 
> With Best Regards,
> Andy Shevchenko