From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758735Ab3BGPXk (ORCPT ); Thu, 7 Feb 2013 10:23:40 -0500 Received: from mail-ia0-f177.google.com ([209.85.210.177]:43538 "EHLO mail-ia0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758208Ab3BGPXi (ORCPT ); Thu, 7 Feb 2013 10:23:38 -0500 MIME-Version: 1.0 In-Reply-To: <5113C459.8000602@synopsys.com> References: <1359475380-31512-1-git-send-email-abrodkin@synopsys.com> <1781360.cmQWHCW5SC@wuerfel> <201302041724.47331.arnd@arndb.de> <1360031367.14701.47.camel@pasglop> <1360066756.4529.6.camel@pasglop> <51111133.7000105@synopsys.com> <1360098004.4529.13.camel@pasglop> <511178AC.7080304@synopsys.com> <1360105635.2707.7.camel@pasglop> <1360186550.2650.4.camel@pasglop> <5113C459.8000602@synopsys.com> From: Grant Likely Date: Thu, 7 Feb 2013 15:23:16 +0000 X-Google-Sender-Auth: GpmKXPn9HAFFhFxEvLMK8RmsmHY Message-ID: Subject: Re: [PATCH] drivers/block/xsysace - replace in(out)_8/in(out)_be16/in(out)_le16 with generic iowrite(read)8/16(be) To: Alexey Brodkin Cc: Benjamin Herrenschmidt , Michal Simek , Arnd Bergmann , Vineet Gupta , Linux Kernel Mailing List , Alan Cox , Geert Uytterhoeven , dahinds@users.sourceforge.net Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 7, 2013 at 3:12 PM, Alexey Brodkin wrote: > On 02/07/2013 06:51 PM, Grant Likely wrote: >> >> On Thu, Feb 7, 2013 at 2:39 PM, Grant Likely >> wrote: >>> >>> On Wed, Feb 6, 2013 at 9:35 PM, Benjamin Herrenschmidt >>> wrote: >>>>> >>>>> In fact, the driver already knows about this and figures >>>>> out at runtime how the device is wired up to the bus. This is not the >>>>> problem. >>>> >>>> >>>> Except that this is very gross, especially when you observe that in the >>>> busted "big endian" case, it has to byteswap the bloody data port. >>>> >>>> So you end up having to do that gross hack with separate accessors for >>>> registers vs. data and not able to use the _rep variants, which also >>>> means that on platforms like ppc, you end up with a memory barrier on >>>> every access (or more), which is going to slow things down enormously. >>> >>> >>> I don't see why the _rep variants aren't usable here. The only reason >>> I didn't use them when I wrote the driver in the first place was I was >>> a n00b kernel hacker and I didn't know they were there. >> >> >> The 8-bit variant is different though because the hardware requires >> pingponging between odd and even byte addresses to flush the fifo. >> Reading a data port even address (0x40) gives the least significant >> byte. Reading from an odd address (0x41) give the MSB and pops the >> data off the FIFO. So, yes, the _rep variant can't be used in 8-bit >> mode. It should still be fine in 16-bit. >> >> page 45: http://www.xilinx.com/support/documentation/data_sheets/ds080.pdf >> > > Ok, so may I do a re-spin with these changes: There are two things here. 1) changing the accessors used. 2) switching the endianess as a bug fix. Any changes to the endian access should be a separate patch which a description of what is needed. > 1. In "ace_in_be16" use "ioread16be" > 2. In "ace_out_be16" use "iowrite16be" > 3. In "ace_in_le16" use "ioread16" > 4. In "ace_out_le16" use "iowrite16" Yes > 5. In "ace_datain_le16" use "ioread16_rep" > 6. In "ace_dataout_le16" use "iowrite16_rep" Maybe. In a separate patch. Hmmm... I guess there isn't an ioread16be_rep variant. Oh well. Check first with Michal on LE microblaze before making the change. If it doesn't work for him the more understanding is needed. I was pretty sure the LE variant already worked. > not sure about items for "ace_datain/out_be16" - what about _rep options > here? ioread16_rep should be fine. The ace_data{in,out}_be16 routines need to use the LE accessor. The existing code is definitely correct in this respect. g.