From: Jiri Slaby <jirislaby@kernel.org>
To: hammer hsieh <hammerh0314@gmail.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
robh+dt@kernel.org, linux-serial@vger.kernel.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
p.zabel@pengutronix.de, wells.lu@sunplus.com,
"hammer.hsieh" <hammer.hsieh@sunplus.com>
Subject: Re: [PATCH v6 2/2] serial:sunplus-uart:Add Sunplus SoC UART Driver
Date: Thu, 13 Jan 2022 10:08:11 +0100 [thread overview]
Message-ID: <d6d3aa07-7bf1-2b6d-356f-ae13c7b9d6cd@kernel.org> (raw)
In-Reply-To: <CAOX-t54oA9V94d3901w2xKSagSzmXc9r=TDTtbgaSLfL1DxNbw@mail.gmail.com>
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
next prev parent reply other threads:[~2022-01-13 9:08 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-12 9:24 [PATCH v6 0/2] Add UART driver for Suplus SP7021 SoC Hammer Hsieh
2022-01-12 9:24 ` [PATCH v6 1/2] dt-bindings:serial:Add bindings doc for Sunplus SoC UART Driver Hammer Hsieh
2022-01-12 9:24 ` [PATCH v6 2/2] serial:sunplus-uart:Add " Hammer Hsieh
2022-01-13 7:06 ` Jiri Slaby
2022-01-13 8:54 ` hammer hsieh
2022-01-13 9:08 ` Jiri Slaby [this message]
2022-01-13 10:56 ` hammer hsieh
2022-01-13 11:12 ` Jiri Slaby
2022-01-14 2:22 ` hammer hsieh
2022-01-26 13:47 ` Greg KH
2022-01-28 3:36 ` hammer hsieh
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