linux-kernel - Re: [PATCH V4] i2c: designware: fix wrong Tx/Rx FIFO for ACPI

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Date:   Tue, 13 Dec 2016 13:25:37 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Tin Huynh <tnhuynh@....com>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Wolfram Sang <wsa@...-dreams.de>
Cc:     linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, Loc Ho <lho@....com>,
        Thang Nguyen <tqnguyen@....com>, Phong Vo <pvo@....com>,
        patches@....com
Subject: Re: [PATCH V4] i2c: designware: fix wrong Tx/Rx FIFO for ACPI

On Tue, 2016-12-13 at 17:03 +0700, Tin Huynh wrote:
> ACPI always sets Tx/Rx FIFO to 32. This configuration will
> cause problem if the IP core supports a FIFO size of less than 32.
> The driver should read the FIFO size from the IP and select the
> smaller
> one of the two.
> 
> Signed-off-by: Tin Huynh <tnhuynh@....com>
> 

One comment below, after addressing it

Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

> ---
>  drivers/i2c/busses/i2c-designware-platdrv.c |   27
> ++++++++++++++++++++-------
>  1 files changed, 20 insertions(+), 7 deletions(-)
> 
> Change from V3:
>  -Use uppercase of FIFO instead of lowercase.
>  -Fix the problem  when IP core return 0 of FIFO.
> 
> Change from V2:
>  -Add a helper function to set FIFO size.
> 
> Change from V1:
>  -Revert the default 32 for FIFO, read parameter from IP core
>  and pick the smaller one of the two.
>  -Correct the title to describe new approach.
> 
> diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c
> b/drivers/i2c/busses/i2c-designware-platdrv.c
> index 0b42a12..24032d6 100644
> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> @@ -150,6 +150,25 @@ static int i2c_dw_plat_prepare_clk(struct
> dw_i2c_dev *i_dev, bool prepare)
>  	return 0;
>  }
>  
> +static void dw_i2c_set_fifo_size(struct dw_i2c_dev *dev, int id)
> +{
> +	u32 param, tx_fifo_depth, rx_fifo_depth;
> +
> 

        /*               
         * Try to detect the FIFO depth if not
set by interface driver,
         * the depth could be from 2 to 256 from
HW spec.
         */     

> +	param = i2c_dw_read_comp_param(dev);
> +	tx_fifo_depth = ((param >> 16) & 0xff) + 1;
> +	rx_fifo_depth = ((param >> 8)  & 0xff) + 1;
> +	if (!dev->tx_fifo_depth) {
> +		dev->tx_fifo_depth = tx_fifo_depth;
> +		dev->rx_fifo_depth = rx_fifo_depth;
> +		dev->adapter.nr = id;
> +	} else if (tx_fifo_depth > 1) {

This makes sense now, though I would add a comment here and use >= 2 to
reflect datasheet.

		/*
                 * Choose minimum values between HW and interface
                 * driver provided.
		 */

> +		dev->tx_fifo_depth = min_t(u32, dev->tx_fifo_depth,
> +				tx_fifo_depth);
> +		dev->rx_fifo_depth = min_t(u32, dev->rx_fifo_depth,
> +				rx_fifo_depth);
> +	}
> +}
> +
>  static int dw_i2c_plat_probe(struct platform_device *pdev)
>  {
>  	struct dw_i2c_platform_data *pdata = dev_get_platdata(&pdev-
> >dev);
> @@ -246,13 +265,7 @@ static int dw_i2c_plat_probe(struct
> platform_device *pdev)
>  				1000000);
>  	}
>  
> -	if (!dev->tx_fifo_depth) {
> -		u32 param1 = i2c_dw_read_comp_param(dev);
> -
> -		dev->tx_fifo_depth = ((param1 >> 16) & 0xff) + 1;
> -		dev->rx_fifo_depth = ((param1 >> 8)  & 0xff) + 1;
> -		dev->adapter.nr = pdev->id;
> -	}
> +	dw_i2c_set_fifo_size(dev, pdev->id);
>  
>  	adap = &dev->adapter;
>  	adap->owner = THIS_MODULE;

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy