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
