From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH 1 of 5] rombios/keyboard: Don't needlessly
 poll the status register
Date: Mon, 26 Nov 2012 16:53:08 +0000
Message-ID: <50B39E74.7080605@citrix.com>
References: <patchbomb.1353948091@andrewcoop.uk.xensource.com>
	<1728fb78994054ad3695.1353948092@andrewcoop.uk.xensource.com>
	<1353948513.5830.117.camel@zakaz.uk.xensource.com>
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To: Ian Campbell <Ian.Campbell@citrix.com>
Cc: "Keir (Xen.org)" <keir@xen.org>, "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
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On 26/11/12 16:48, Ian Campbell wrote:
> On Mon, 2012-11-26 at 16:41 +0000, Andrew Cooper wrote:
>> Repeated polling of the status register is not going to change its value,
> but the passage of time while doing multiple polls might? If this is not
> the case then something needs to be said about why not.

In reality, we failed to ever get a keypress on the console to appear
here, even when trying.  If I remember correctly (it was a long time ago
now), this code runs before the PCI bus is scanned, so is really early
on during boot.

>
>>  so
>> don't needlessly take 8192 traps to Qemu when 1 will do.
>>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
>>
>> diff -r 0049de3827bc -r 1728fb789940 tools/firmware/rombios/rombios.c
>> --- a/tools/firmware/rombios/rombios.c
>> +++ b/tools/firmware/rombios/rombios.c
>> @@ -1805,12 +1805,12 @@ keyboard_init()
>>      while ( (inb(0x64) & 0x02) && (--max>0)) outb(0x80, 0x00);
>>  
>>      /* flush incoming keys */
>> -    max=0x2000;
>> +    max=2;
>>      while (--max > 0) {
>>          outb(0x80, 0x00);
>>          if (inb(0x64) & 0x01) {
>>              inb(0x60);
>> -            max = 0x2000;
>> +            max = 2;
>>              }
>>          }
>>  
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xen.org
>> http://lists.xen.org/xen-devel
>

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com