Re: [PATCH 1/2] i2c: cadence: Allow to specify the FIFO depth and maximum transfer length

[Michal Simek <michal.simek@amd.com>]

On 2/16/23 15:12, Lars-Peter Clausen wrote:
> On 2/6/23 00:02, Michal Simek wrote:
>>
>>
>> On 2/6/23 00:02, Lars-Peter Clausen wrote:
>>> The FIFO depth and maximum transfer length are Synthesis configuration
>>> parameters of the Cadence I2C IP. Different SoCs will use different values
>>> for these parameters.
>>>
>>> Currently the driver has the FIFO depth hardcoded to 16 and the maximum
>>> transfer length to 255. Trying to use the driver with an IP instance that
>>> uses smaller values for these will work for short transfers. But longer
>>> transfers will fail.
>>>
>>> The maximum transfer length can easily be detected at runtime since the
>>> unused MSBs of the transfer length register are hardwired to 0. Writing
>>> 0xff and then reading back the value will give the maximum transfer length.
>>
>> I think that these are pretty much two patches in one.
>> The first should target transfer length part and second fifo depth part.
> Hm, I'm not sure it is worth separating this out. These two are very tightly 
> related, but I can split it.

thanks

>>
>>>   /**
>>>    * cdns_i2c_probe - Platform registration call
>>>    * @pdev:    Handle to the platform device structure
>>> @@ -1242,6 +1274,7 @@ static int cdns_i2c_probe(struct platform_device *pdev)
>>>       struct cdns_i2c *id;
>>>       int ret, irq;
>>>       const struct of_device_id *match;
>>> +    u32 val;
>>>         id = devm_kzalloc(&pdev->dev, sizeof(*id), GFP_KERNEL);
>>>       if (!id)
>>> @@ -1317,6 +1350,12 @@ static int cdns_i2c_probe(struct platform_device *pdev)
>>>   #endif
>>>       id->ctrl_reg = CDNS_I2C_CR_ACK_EN | CDNS_I2C_CR_NEA | CDNS_I2C_CR_MS;
>>>   +    val = CDNS_I2C_FIFO_DEPTH_DEFAULT;
>>
>> you can remove val completely.
>> id->fifo_depth = CDNS_I2C_FIFO_DEPTH_DEFAULT;
> But only if I make fifo_depth a u32.

No problem for me.

M