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

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Date:   Wed, 14 Dec 2016 10:59:08 +0200
From:   Jarkko Nikula <jarkko.nikula@...ux.intel.com>
To:     Tin Huynh <tnhuynh@....com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Wolfram Sang <wsa@...-dreams.de>, 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 <patches@....com>
Subject: Re: [PATCH V4] i2c: designware: fix wrong Tx/Rx FIFO for ACPI

On 12/14/2016 05:20 AM, Tin Huynh wrote:
> On Tue, Dec 13, 2016 at 6:25 PM, Andy Shevchenko
>>> +     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.
>>                  */
>>
> I will implement as your comment. However , because adding 1 to the
> value , can i use > 2  or >=3 ?

either > 1 or >= 2 since register value 0x01 from HW means FIFO depth 2 
and register value 0x00 is reserved.

-- 
Jarkko