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Re: [U-Boot] [PATCH 3/3] ARM: tegra: paz00: enable nveckeyboardsupport


On 07/24/2013 10:52 AM, Marc Dietrich wrote:
> On Tuesday 23 July 2013 08:40:42 Stephen Warren wrote:
>> On 07/22/2013 01:09 AM, Marc Dietrich wrote:
> [ snip the stuff we agreed upon ]
>>> The nvec still needs to tell the slave driver which protocol to use, but
>>> that can be hard coded.
>> I'm not sure what that means. At the controller/HW level, aren't I2C and
>> SMBUS the same; it's just the data within the transactions that may be
>> more defined by one or the other?
> at this level yes, but we need to handle the underlying protocol in the ISR, 
> which means that depending on the protocol (smbus or I2C), we need a different 
> interrupt service routine. Currently we are doing most of the smbus protocol 
> in the ISR because of timing reasons and I'm not sure if we can change this. 
> We are already suffering from nvec timeouts and I fear that splitting the 
> protocol out of the ISR would make things even worse.

I assume that the I2C slave driver's ISR would simply
directly/immediately call a function in the "protocol driver". That
should allow sufficient separation of the layers while still maintaining
minimal latency, assuming a good design of the callback's function
prototype and/or the list of I2C slave controller functions that the
callback is allowed to call into.