On 10/11/2014 21:11, Hannes Reinecke wrote: > On 11/10/2014 07:32 PM, Paolo Bonzini wrote: >> On 10/11/2014 16:52, Hannes Reinecke wrote: >>> After a reset ESP_TCHI should contain the unique ID >>> of the chip. This value will be overwritten with the >>> current tranfer count if the transfer count has >>> previously been set. >>> So we should always return the chip id if ESP_TCHI >>> has never been written to. >> >> What if ESP_TCHI was written 0? Why should it return the chip id? >> > It's a complex thing. The documentation says 'ESP_TCHI returns the chip > id until been written to'. > And ESP_TCHI is strictly speaking only valid if the 'Features enabled' > bit is set in ESP_CFG2. (Not that the driver checks this). > To handle it correctly we would need to add a flag whenever ESP_TCHI > is written to, but I thought it'd be slightly too much.
I'm worried that the chip_id will reappear if you write a low (<65536) value to ESP_TCLOW/MED/HI. Adding the flag is just a couple lines more than this patch, let's do it right. Paolo
