Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754687Ab2JBPvz (ORCPT ); Tue, 2 Oct 2012 11:51:55 -0400 Received: from mail-vc0-f174.google.com ([209.85.220.174]:47364 "EHLO mail-vc0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753838Ab2JBPvx (ORCPT ); Tue, 2 Oct 2012 11:51:53 -0400 MIME-Version: 1.0 In-Reply-To: <506ACC77.9090604@ti.com> References: <1348861072-14507-1-git-send-email-mporter@ti.com> <1348861072-14507-5-git-send-email-mporter@ti.com> <506986B2.1030000@ti.com> <20121001123242.GJ5641@beef> <506ACC77.9090604@ti.com> Date: Tue, 2 Oct 2012 11:51:52 -0400 Message-ID: Subject: Re: [PATCH v2 4/7] ARM: davinci: Add support for an L3RAM gen_pool From: Ben Gardiner To: Sekhar Nori Cc: Matt Porter , Linux DaVinci Kernel List , Paul Walmsley , Russell King , Benoit Cousson , Tony Lindgren , Greg Kroah-Hartman , Linux Kernel Mailing List , "Hans J. Koch" , Linux OMAP List , Linux ARM Kernel List , Subhasish Ghosh 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 Content-Length: 3514 Lines: 72 On Tue, Oct 2, 2012 at 7:13 AM, Sekhar Nori wrote: > On 10/1/2012 7:20 PM, Ben Gardiner wrote: >> On Mon, Oct 1, 2012 at 8:32 AM, Matt Porter wrote: >>> On Mon, Oct 01, 2012 at 05:34:02PM +0530, Sekhar Nori wrote: >>>> Hi Matt, >>>> >>>> On 9/29/2012 1:07 AM, Matt Porter wrote: >>>>> L3RAM (shared SRAM) is needed for use by several drivers. >>>>> This creates a genalloc pool and a hook for the platform code >>>>> to provide the struct gen_pool * in platform data. >>>>> >>>>> Signed-off-by: Matt Porter >>>> >>>> I am not sure if any of the DaVinci devices have a need to allocate from >>>> *both* ARM RAM and shared RAM. Shared RAM is not present on all DaVinci >>>> devices AFAIR, and on DA850, there is just 8KB ARM RAM so I am not sure >>>> if there is much point in trying to allocate from there. >>>> >>>> Can you instead see if Ben's earlier patch[1] to use shared RAM for SRAM >>>> allocation on DA850 makes sense for your case? If yes, can you repost >>>> with Ben's patch included in your series instead of this patch? I would >>>> prefer that over creating a new pool for shared RAM. >>> >>> Hrm, I did look at Ben's earlier patch. The reason I added a separate >>> pool mostly was so I didn't have to touch the PM code at all. That can >>> continue using the private SRAM API with the ARM RAM as it is now. The >>> idea here was to allow that to be separate since no other bus masters >>> can access the ARM RAM anyway and do something that didn't require >>> regression testing PM. Also, I figured there's really no reason to use >>> even a tiny bit of the shared SRAM on PM if we have that ARM RAM there >>> and working fine for that use case. >>> [...] >> >> I agree with Matt. Preserving the use of the ARM RAM (8K on L138 -- as >> you said, Sekhar) in any fashion is preferable to moving suspend >> support into shared RAM. There is more of it (128K on L138) but also >> more pressure on allocations there since there are more clients. > > There is where I would like to see more information on who the potential > clients are. Even if DSP takes away 64K of the shared RAM on OMAP-L138, > there should be more than enough for PM, Audio and PRU. I haven't > checked the PM code size lately but it should be fairly small and I can > check the actual number if that helps. So, adding a new pool just to > save on those bytes doesn't sound like helping a lot. Good points. I suppose that the list would decrease also on L138 if davinci-pcm ping-pong buffers were removed from SRAM. >> I appreciate that you are trying to preserve prior efforts in >> attempted merging of SRAM support -- thank you for that; however, that >> patch [1] was just an import of Subashish Ghosh's patch [2] -- I >> chose _that_ implementation option then mainly because I imagined it >> would be the least risky to get accepted upstream and not because of >> any particular technical merits. > > Its not a question of prior effort since Matt has already put in the > effort too. I am yet unconvinced that we need to add support to manage > two blocks of SoC internal RAM on DA850 in the kernel today. That's all. Understood. Thank you, Sekhar. Best Regards, Ben Gardiner --- Nanometrics Inc. http://www.nanometrics.ca -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/