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SubjectRe: [PATCH v6 2/2] serial:sunplus-uart:Add Sunplus SoC UART Driver
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On 13. 01. 22, 9:54, hammer hsieh wrote:
>>> +static void sunplus_shutdown(struct uart_port *port)
>>> +{
>>> + unsigned long flags;
>>> +
>>> + spin_lock_irqsave(&port->lock, flags);
>>> + writel(0, port->membase + SUP_UART_ISC);
>>> + spin_unlock_irqrestore(&port->lock, flags);
>>
>> I asked last time:
>> * What bus is this -- posting?
>>
>> You replied:
>> * Here just clear interrupt.
>> * Not really understand your comment?
>>
>> So I am asking again:
>> What bus is this? Isn't a posted write a problem here? I mean, shouldn't
>> you read from the register so that the write hits the device? That
>> depends on the bus this sits on, so just asking.
>>
>
> Each UART has its own ISC register.
> Ex.
> dev/ttySUP0 base_adr = 0x9C00-0000 , isc_addr = 0x9C00-001C
> dev/ttySUP1 base_adr = 0x9C00-0080 , isc_addr = 0x9C00-009C
> dev/ttySUP2 base_adr = 0x9C00-0100 , isc_addr = 0x9C00-011C
> dev/ttySUP3 base_adr = 0x9C00-0180 , isc_addr = 0x9C00-019C
> dev/ttySUP4 base_adr = 0x9C00-0200 , isc_addr = 0x9C00-021C
> So sunplus_shutdown() just simply turn off its own device isc only.
> That's why I didn't read register value, just write 0 for it.

Could you explain me what posted write is and how does it not matter in
this case?

thanks,
--
js
suse labs

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