From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Lindgren Subject: Re: [PATCH 3/3] hvc_dcc: Simplify assembly for v6 and v7 ARM Date: Tue, 4 Jan 2011 10:52:56 -0800 Message-ID: <20110104185256.GD7771@atomide.com> References: <1292649385-28771-1-git-send-email-sboyd@codeaurora.org> <1292875718-7980-1-git-send-email-sboyd@codeaurora.org> <1292875718-7980-4-git-send-email-sboyd@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mho-01-ewr.mailhop.org ([204.13.248.71]:31181 "EHLO mho-01-ewr.mailhop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751127Ab1ADSxD (ORCPT ); Tue, 4 Jan 2011 13:53:03 -0500 Content-Disposition: inline In-Reply-To: Sender: linux-arm-msm-owner@vger.kernel.org List-Id: linux-arm-msm@vger.kernel.org To: Nicolas Pitre Cc: Stephen Boyd , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Arnd Bergmann , Daniel Walker * Nicolas Pitre [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 > > Cc: Arnd Bergmann > > Cc: Nicolas Pitre > > Cc: Daniel Walker > > Signed-off-by: Stephen Boyd > > Acked-by: Nicolas Pitre Acked-by: Tony Lindgren From mboxrd@z Thu Jan 1 00:00:00 1970 From: tony@atomide.com (Tony Lindgren) Date: Tue, 4 Jan 2011 10:52:56 -0800 Subject: [PATCH 3/3] hvc_dcc: Simplify assembly for v6 and v7 ARM In-Reply-To: References: <1292649385-28771-1-git-send-email-sboyd@codeaurora.org> <1292875718-7980-1-git-send-email-sboyd@codeaurora.org> <1292875718-7980-4-git-send-email-sboyd@codeaurora.org> Message-ID: <20110104185256.GD7771@atomide.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org * Nicolas Pitre [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 > > Cc: Arnd Bergmann > > Cc: Nicolas Pitre > > Cc: Daniel Walker > > Signed-off-by: Stephen Boyd > > Acked-by: Nicolas Pitre Acked-by: Tony Lindgren