Re: [PATCH v13 2/3] i2c: aspeed: support AST2600 i2c new register mode driver

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Thu, Aug 22, 2024 at 02:24:26AM +0000, Ryan Chen wrote:
> > On Wed, Aug 21, 2024 at 06:43:01AM +0000, Ryan Chen wrote:
> > > > On Mon, Aug 19, 2024 at 05:28:49PM +0800, Ryan Chen wrote:

...

> > > > > +	/* Check 0x14's SDA and SCL status */
> > > > > +	state = readl(i2c_bus->reg_base + AST2600_I2CC_STS_AND_BUFF);
> > > > > +	if (!(state & AST2600_I2CC_SDA_LINE_STS) && (state &
> > > > AST2600_I2CC_SCL_LINE_STS)) {
> > > > > +		writel(AST2600_I2CM_RECOVER_CMD_EN, i2c_bus->reg_base
> > +
> > > > AST2600_I2CM_CMD_STS);
> > > > > +		r = wait_for_completion_timeout(&i2c_bus->cmd_complete,
> > > > i2c_bus->adap.timeout);
> > > > > +		if (r == 0) {
> > > > > +			dev_dbg(i2c_bus->dev, "recovery timed out\n");
> > > > > +			ret = -ETIMEDOUT;
> > > > > +		} else {
> > > > > +			if (i2c_bus->cmd_err) {
> > > > > +				dev_dbg(i2c_bus->dev, "recovery error\n");
> > > > > +				ret = -EPROTO;
> > > > > +			}
> > > > > +		}
> > > > > +	}
> > > >
> > > > ret is set but maybe overridden.
> > >
> > > If will modify by following.
> > > 		if (r == 0) {
> > > 			dev_dbg(i2c_bus->dev, "recovery timed out\n");
> > > 			ret = -ETIMEDOUT;
> > > 		} else if (i2c_bus->cmd_err) {
> > > 			dev_dbg(i2c_bus->dev, "recovery error\n");
> > > 			ret = -EPROTO;
> > > 		}
> > > If no error keep ret = 0;
> > 
> > It doesn't change the behaviour. Still ret can be overridden below...
> 
> Yes, it is expectable, previous is issue recovery command out then the
> following is double confirm the bus status.
> If bus still busy, the function still return recovery fail.
> 
> Or should I modify by following?
> 	/* Check 0x14's SDA and SCL status */
> 	state = readl(i2c_bus->reg_base + AST2600_I2CC_STS_AND_BUFF);
> 	if (!(state & AST2600_I2CC_SDA_LINE_STS) && (state & AST2600_I2CC_SCL_LINE_STS)) {
> 		writel(AST2600_I2CM_RECOVER_CMD_EN, i2c_bus->reg_base + AST2600_I2CM_CMD_STS);
> 		r = wait_for_completion_timeout(&i2c_bus->cmd_complete, i2c_bus->adap.timeout);
> 		if (r == 0) {
> 			dev_dbg(i2c_bus->dev, "recovery timed out\n");

> 			ret = -ETIMEDOUT;

This assignment doesn't make sense.

> 		} else if (i2c_bus->cmd_err) {
> 				dev_dbg(i2c_bus->dev, "recovery error\n");
> 				ret = -EPROTO;
> 		}
> 		/* check bus status */
> 		state = readl(i2c_bus->reg_base + AST2600_I2CC_STS_AND_BUFF);
> 		if (state & AST2600_I2CC_BUS_BUSY_STS) {
> 			dev_dbg(i2c_bus->dev, "Can't recover bus [%x]\n", state);
> 			ret = -EPROTO;
> 		}
> 	}

> > > > > +	/* Recovery done */
> > > >
> > > > Even if it fails above?
> > >
> > > This will keep check the bus status, if bus busy, will give ret =
> > > -EPROTO;
> > >
> > > > > +	state = readl(i2c_bus->reg_base + AST2600_I2CC_STS_AND_BUFF);
> > > > > +	if (state & AST2600_I2CC_BUS_BUSY_STS) {
> > > > > +		dev_dbg(i2c_bus->dev, "Can't recover bus [%x]\n", state);
> > > > > +		ret = -EPROTO;
> > 
> > ...here.

See above.

> > > > > +	}
> > > > > +
> > > > > +	/* restore original master/slave setting */
> > > > > +	writel(ctrl, i2c_bus->reg_base + AST2600_I2CC_FUN_CTRL);
> > > > > +	return ret;

...

> > > > > +		i2c_bus->master_dma_addr =
> > > > > +			dma_map_single(i2c_bus->dev, i2c_bus->master_safe_buf,
> > > > > +				       msg->len, DMA_TO_DEVICE);
> > > >
> > > > > +		if (dma_mapping_error(i2c_bus->dev,
> > i2c_bus->master_dma_addr))
> > > > {
> > > > > +			i2c_put_dma_safe_msg_buf(i2c_bus->master_safe_buf,
> > msg,
> > > > false);
> > > > > +			i2c_bus->master_safe_buf = NULL;
> > > >
> > > > > +			return -ENOMEM;
> > > >
> > > > Why is the dma_mapping_error() returned error code shadowed?
> > >
> > > Sorry, please point me why you are think it is shadowed?
> > > As I know dma_mapping_error() will return 0 or -ENOMEM. So I check if it
> > is !=0.
> > > Than return -ENOMEM.
> > 
> > First of all, it is a bad style to rely on the implementation details where it's not
> > crucial. Second, today it may return only ENOMEM, tomorrow it can return a
> > different code or codes. And in general, one should not shadow an error code
> > without justification.
> > 
> Understood, The following is better, am I right? (if yest, those will update in driver)

Yes.

> 		Int ret;
> 		.....
> 		ret = dma_mapping_error(i2c_bus->dev, i2c_bus->master_dma_addr)
> 		if (ret) {
> 			i2c_put_dma_safe_msg_buf(i2c_bus->master_safe_buf, msg, false);
> 			i2c_bus->master_safe_buf = NULL;
> 			return ret;
> 		}
> 
> > > > > +		}

...

> > > > > +	if (i2c_bus->mode == BUFF_MODE) {
> > > > > +		i2c_bus->buf_base =
> > > > devm_platform_get_and_ioremap_resource(pdev, 1, &res);
> > > > > +		if (!IS_ERR_OR_NULL(i2c_bus->buf_base))
> > > > > +			i2c_bus->buf_size = resource_size(res) / 2;
> > > > > +		else
> > > > > +			i2c_bus->mode = BYTE_MODE;
> > > >
> > > > What's wrong with positive conditional? And is it even possible to
> > > > have NULL here?
> > > >
> > > Yes, if dtsi fill not following yaml example have reg 1, that will failure at buffer
> > mode.
> > > And I can swith to byte mode.
> > >
> > > reg = <0x80 0x80>, <0xc00 0x20>;
> > 
> > I was asking about if (!IS_ERR_OR_NULL(...)) line:
> > 1) Why 'if (!foo) {} else {}' instead of 'if (foo) {} else {}'?
> I will update to following.
> 		if (IS_ERR(i2c_bus->buf_base))
> 			i2c_bus->mode = BYTE_MODE;
> 		else
> 			i2c_bus->buf_size = resource_size(res) / 2;
> 
> > 2) Why _NULL?
> 	If dtsi file is claim only 1 reg offset. reg = <0x80 0x80>; that will goto byte mode.
> 	reg = <0x80 0x80>, <0xc00 0x20>; can support buffer mode.
> 	due to 2nd is buffer register offset.

I have asked why IS_ERR_OR_NULL() and not IS_ERR().

> > > > > +	}

-- 
With Best Regards,
Andy Shevchenko