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From: Tony Lindgren <tony@atomide.com>
To: Nicolas Pitre <nico@fluxnic.net>
Cc: Stephen Boyd <sboyd@codeaurora.org>,
	Greg Kroah-Hartman <gregkh@suse.de>,
	linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Arnd Bergmann <arnd@arndb.de>,
	Daniel Walker <dwalker@codeaurora.org>
Subject: Re: [PATCH 3/3] hvc_dcc: Simplify assembly for v6 and v7 ARM
Date: Tue, 4 Jan 2011 10:52:56 -0800	[thread overview]
Message-ID: <20110104185256.GD7771@atomide.com> (raw)
In-Reply-To: <alpine.LFD.2.00.1012201644110.10437@xanadu.home>

* Nicolas Pitre <nico@fluxnic.net> [101220 13:44]:
> On Mon, 20 Dec 2010, Stephen Boyd wrote:
> 
> > The inline assembly differences for v6 vs. v7 in the hvc_dcc
> > driver are purely optimizations. On a v7 processor, an mrc with
> > the pc sets the condition codes to the 28-31 bits of the register
> > being read. It just so happens that the TX/RX full bits the DCC
> > driver is testing for are high enough in the register to be put
> > into the condition codes. On a v6 processor, this "feature" isn't
> > implemented and thus we have to do the usual read, mask, test
> > operations to check for TX/RX full.
> > 
> > Since we already test the RX/TX full bits before calling
> > __dcc_getchar() and __dcc_putchar() we don't actually need to do
> > anything special for v7 over v6. The only difference is in
> > hvc_dcc_get_chars(). We would test RX full, poll RX full, and
> > then read a character from the buffer, whereas now we will test
> > RX full, read a character from the buffer, and then test RX full
> > again for the second iteration of the loop. It doesn't seem
> > possible for the buffer to go from full to empty between testing
> > the RX full and reading a character. Therefore, replace the v7
> > versions with the v6 versions and everything works the same.
> > 
> > Cc: Tony Lindgren <tony@atomide.com>
> > Cc: Arnd Bergmann <arnd@arndb.de>
> > Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
> > Cc: Daniel Walker <dwalker@codeaurora.org>
> > Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
> 
> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>

Acked-by: Tony Lindgren <tony@atomide.com>

WARNING: multiple messages have this Message-ID (diff)
From: tony@atomide.com (Tony Lindgren)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 3/3] hvc_dcc: Simplify assembly for v6 and v7 ARM
Date: Tue, 4 Jan 2011 10:52:56 -0800	[thread overview]
Message-ID: <20110104185256.GD7771@atomide.com> (raw)
In-Reply-To: <alpine.LFD.2.00.1012201644110.10437@xanadu.home>

* Nicolas Pitre <nico@fluxnic.net> [101220 13:44]:
> On Mon, 20 Dec 2010, Stephen Boyd wrote:
> 
> > The inline assembly differences for v6 vs. v7 in the hvc_dcc
> > driver are purely optimizations. On a v7 processor, an mrc with
> > the pc sets the condition codes to the 28-31 bits of the register
> > being read. It just so happens that the TX/RX full bits the DCC
> > driver is testing for are high enough in the register to be put
> > into the condition codes. On a v6 processor, this "feature" isn't
> > implemented and thus we have to do the usual read, mask, test
> > operations to check for TX/RX full.
> > 
> > Since we already test the RX/TX full bits before calling
> > __dcc_getchar() and __dcc_putchar() we don't actually need to do
> > anything special for v7 over v6. The only difference is in
> > hvc_dcc_get_chars(). We would test RX full, poll RX full, and
> > then read a character from the buffer, whereas now we will test
> > RX full, read a character from the buffer, and then test RX full
> > again for the second iteration of the loop. It doesn't seem
> > possible for the buffer to go from full to empty between testing
> > the RX full and reading a character. Therefore, replace the v7
> > versions with the v6 versions and everything works the same.
> > 
> > Cc: Tony Lindgren <tony@atomide.com>
> > Cc: Arnd Bergmann <arnd@arndb.de>
> > Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
> > Cc: Daniel Walker <dwalker@codeaurora.org>
> > Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
> 
> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>

Acked-by: Tony Lindgren <tony@atomide.com>

  reply	other threads:[~2011-01-04 18:53 UTC|newest]

Thread overview: 79+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-11-30 19:25 [PATCH] drivers: char: hvc: add arm JTAG DCC console support Daniel Walker
2010-11-30 19:25 ` Daniel Walker
2010-11-30 19:57 ` Nicolas Pitre
2010-11-30 19:57   ` Nicolas Pitre
2010-11-30 21:17   ` Arnd Bergmann
2010-11-30 21:17     ` Arnd Bergmann
2010-12-01  5:30 ` Stephen Boyd
2010-12-01  5:30   ` Stephen Boyd
2010-12-01 18:54   ` Daniel Walker
2010-12-01 18:54     ` Daniel Walker
2010-12-01 19:28     ` Greg KH
2010-12-01 19:28       ` Greg KH
2010-12-18  5:16       ` [PATCH] hvc_dcc: Simplify assembly for v6 and v7 ARM Stephen Boyd
2010-12-18  5:16         ` Stephen Boyd
2010-12-20 17:51         ` Daniel Walker
2010-12-20 17:51           ` Daniel Walker
2010-12-20 18:39           ` Stephen Boyd
2010-12-20 18:39             ` Stephen Boyd
2010-12-20 18:46             ` Nicolas Pitre
2010-12-20 18:46               ` Nicolas Pitre
2010-12-20 20:08         ` [PATCH 0/3] hvc_dcc cleanups and fixes Stephen Boyd
2010-12-20 20:08           ` Stephen Boyd
2010-12-20 20:08           ` [PATCH 1/3] hvc_dcc: Fix bad code generation by marking assembly volatile Stephen Boyd
2010-12-20 20:08             ` Stephen Boyd
2010-12-20 21:39             ` Nicolas Pitre
2010-12-20 21:39               ` Nicolas Pitre
2011-01-02  9:00               ` Pavel Machek
2011-01-02  9:00                 ` Pavel Machek
2011-01-02 18:49                 ` David Brown
2011-01-02 18:49                   ` David Brown
2011-01-03  5:50                   ` Pavel Machek
2011-01-03  5:50                     ` Pavel Machek
2011-01-04 18:49               ` Tony Lindgren
2011-01-04 18:49                 ` Tony Lindgren
2010-12-20 21:49             ` Arnaud Lacombe
2010-12-20 21:49               ` Arnaud Lacombe
2010-12-20 21:52               ` Stephen Boyd
2010-12-20 21:52                 ` Stephen Boyd
2010-12-20 22:10                 ` Nicolas Pitre
2010-12-20 22:10                   ` Nicolas Pitre
2010-12-20 20:08           ` [PATCH 2/3] hvc_dcc: Simplify put_chars()/get_chars() loops Stephen Boyd
2010-12-20 20:08             ` Stephen Boyd
2010-12-20 20:08           ` [PATCH 3/3] hvc_dcc: Simplify assembly for v6 and v7 ARM Stephen Boyd
2010-12-20 20:08             ` Stephen Boyd
2010-12-20 21:44             ` Nicolas Pitre
2010-12-20 21:44               ` Nicolas Pitre
2011-01-04 18:52               ` Tony Lindgren [this message]
2011-01-04 18:52                 ` Tony Lindgren
2011-01-06  1:49           ` [PATCH 0/3] hvc_dcc cleanups and fixes Stephen Boyd
2011-01-06  1:49             ` Stephen Boyd
2011-01-06  3:20             ` Greg KH
2011-01-06  3:20               ` Greg KH
2011-02-03 22:17           ` Greg KH
2011-02-03 22:17             ` Greg KH
2011-02-03 22:17             ` Greg KH
2011-02-03 23:19             ` Stephen Boyd
2011-02-03 23:19               ` Stephen Boyd
2011-02-03 23:30               ` Greg KH
2011-02-03 23:30                 ` Greg KH
2011-02-03 23:48             ` [PATCHv2 " Stephen Boyd
2011-02-03 23:48               ` Stephen Boyd
2011-02-03 23:48               ` [PATCHv2 1/3] hvc_dcc: Fix bad code generation by marking assembly volatile Stephen Boyd
2011-02-03 23:48                 ` Stephen Boyd
2011-02-03 23:48               ` [PATCHv2 2/3] hvc_dcc: Simplify put_chars()/get_chars() loops Stephen Boyd
2011-02-03 23:48                 ` Stephen Boyd
2011-02-03 23:48               ` [PATCHv2 3/3] hvc_dcc: Simplify assembly for v6 and v7 ARM Stephen Boyd
2011-02-03 23:48                 ` Stephen Boyd
2010-12-01 20:20     ` [PATCH] drivers: char: hvc: add arm JTAG DCC console support Stephen Boyd
2010-12-01 20:20       ` Stephen Boyd
2010-12-07 19:10       ` Stephen Boyd
2010-12-07 19:10         ` Stephen Boyd
2011-01-14 19:19         ` Tony Lindgren
2011-01-14 19:19           ` Tony Lindgren
2011-01-14 23:49           ` Stephen Boyd
2011-01-14 23:49             ` Stephen Boyd
2011-04-07 18:39 ` RONETIX - Asen Dimov
2011-04-07 18:39   ` RONETIX - Asen Dimov
2011-04-07 18:57   ` Mike Frysinger
2011-04-07 18:57     ` Mike Frysinger

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