RE: [PATCH] serial: sh-sci: correct units in comment about DMA timeout

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Hi Ulrich-san,

> From: Ulrich Hecht, Sent: Monday, April 12, 2021 5:04 PM
> 
> > On 04/12/2021 8:23 AM Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx> wrote:
> > Hmm, when we use HSCIF with 10 bits, 3000000 baud and 128 bytes FIFO,
> > the rx_timeout value will be set to 1536 (us). So, if we set rx_timeout
> > to 20000 (us) as a minimum value, the sh-sci' behavior will be back to
> > non hrtimer support, IIUC.
> >
> > Perhaps, describing uart_update_timeout() and the jiffies value of
> > uart_port->timeout with 115200 baud here may cause misreading??
> > I didn't understand the purpose of uart_port->timeout yet thought.
> > But, at least, the current driver uses hrtimer to improve latency
> > for HSCIF, the driver should not set 20000 (us) as a minimum value.
> 
> Not having looked at this stuff in a while, I was under the impression that the rx timeout is an error condition, when
> it is in fact part of normal (DMA) operation. I think it was indeed the reference to uart_update_timeout() that threw
> me off...

I think so...

> So if my understanding is correct now, we should scrap the minimum timeout code entirely because the condition it is supposed
> to prevent cannot occur any longer due to the switch to hrtimers. Did I get that right?

Yes, this is the same as my understanding.

Best regards,
Yoshihiro Shimoda

> CU
> Uli




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