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From: Maarten Brock <m.brock@vanmierlo.com>
To: Shubhrajyoti Datta <shubhraj@xilinx.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
	linux-serial@vger.kernel.org, jirislaby@kernel.org,
	jacmet@sunsite.dk, git <git@xilinx.com>,
	michal.simek@xilinx.com
Subject: Re: [PATCH v2] serial-uartlite: Remove an un-necessary read of control register
Date: Fri, 26 Nov 2021 15:07:44 +0100	[thread overview]
Message-ID: <cd14525f12ea09fe85d9db18712ae20a@vanmierlo.com> (raw)
In-Reply-To: <MN2PR02MB664063C64EA9C8BC59C3E566AA619@MN2PR02MB6640.namprd02.prod.outlook.com>

+ Michal

On 2021-11-24 13:37, Shubhrajyoti Datta wrote:
>> -----Original Message-----
>> From: Greg KH <gregkh@linuxfoundation.org>
>> Sent: Wednesday, November 24, 2021 3:38 PM
>> To: Shubhrajyoti Datta <shubhraj@xilinx.com>
>> Cc: linux-serial@vger.kernel.org; jirislaby@kernel.org; 
>> jacmet@sunsite.dk; git
>> <git@xilinx.com>
>> Subject: Re: [PATCH v2] serial-uartlite: Remove an un-necessary read 
>> of control
>> register
>> 
>> On Tue, Nov 23, 2021 at 06:43:48PM +0530, Shubhrajyoti Datta wrote:
>> > The control register is a writeonly register that's why reading it
>> > doesn't make any sense.
>> > The manual states "This is a write-only register. Issuing a read
>> > request to the control register generates the read acknowledgment with zero
>> data."
>> 
>> Are you sure this is ok to remove?  Usually you have to do a read 
>> after a write to
>> ensure that the write succeeded.
>> 
>> What ensures that the write succeeded now if you remove this read?
> 
> I do not find the mention of a read requirement in the manual.
> Also in the current code in ulite_console_write and in ulite_startup
> we are writing without a read.
> 
> Thanks and Regards,
> Shubhrajyoti

I suggest to confer with Michal Simek. He introduced the read in 
ulite_request_port()
in the past. The other one in ulite_shutdown() has been there since its 
inception in
2006.

Maarten


  parent reply	other threads:[~2021-11-26 14:40 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-23 13:13 [PATCH v2] serial-uartlite: Remove an un-necessary read of control register Shubhrajyoti Datta
2021-11-24 10:07 ` Greg KH
2021-11-24 12:37   ` Shubhrajyoti Datta
2021-11-24 12:45     ` Greg KH
2021-11-26 14:07     ` Maarten Brock [this message]
2021-12-15 11:56       ` Michal Simek

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