Re: [virtio-dev] [PATCH v4] virtio-spi: add the device specification

On 11/9/2023 9:11 PM, Mark Brown wrote:
> On Thu, Nov 09, 2023 at 07:21:57PM +0800, Haixu Cui wrote:
> 
>>     For checking the parameters above in virtio_spi_transfer_head, I'd like
>> to add these field in config space:
> 
>>      5. freq_max_speed: if non-zero, maximum clock rate support, in Hz
>>                  unit. if 0, no limitation.
>>
>>      6. max_word_delay_ns: if non-zero, the maximum word delay supported.
>>                  if 0, word delay is not supported to introduce.
>>
>>      7. max_delay_after_cs_asserted: if non-zero, the maximum cs setup
>>                  delay supported.if 0, cs setup delay is not supported to
>>                  introduce
>>
>>      8. max_delay_before_cs_deassert: if non-zero, the maximum
>>                  cs_delay_hold_ns delay supported.if 0, cs setup delay is
>>                  not supported to introduce
>>
>>      9. max_delay_after_cs_deassert: if non-zero, the maximum
>>                  cs_change_delay_inactive_ns delay supported.if 0, cs
>>                  setup delay is not supported to introduce
> 
> I think this all makes sense - for the above we probably also need to
> say that if the value requested by the client can't be met exactly we
> either treat it as a minimum or maximum depending on the delays and
> choose the next value (probably a maximum for the clock and minimum for
> the rest).  So for example if the client requests 21MHz and the
> controller can only select 20MHz or 25MHz then it should pick 20MHz.

Sure, I will update to make it more flexible.

Thanks a lot.

Best Regards
Haixu Cui

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