Messages in this thread | | | Date | Thu, 13 Jan 2022 10:08:11 +0100 | Subject | Re: [PATCH v6 2/2] serial:sunplus-uart:Add Sunplus SoC UART Driver | From | Jiri Slaby <> |
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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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