From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752009AbcF0S2A (ORCPT ); Mon, 27 Jun 2016 14:28:00 -0400 Received: from mail-vk0-f53.google.com ([209.85.213.53]:34524 "EHLO mail-vk0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751748AbcF0S14 (ORCPT ); Mon, 27 Jun 2016 14:27:56 -0400 MIME-Version: 1.0 In-Reply-To: References: <1463704347-22550-1-git-send-email-hotran@apm.com> <0f07c6dc-76b7-ab28-541b-090f6a2432a6@codeaurora.org> <4652800c-b518-6b9a-967f-bb31e6a496b0@codeaurora.org> From: Hoan Tran Date: Mon, 27 Jun 2016 11:27:42 -0700 Message-ID: Subject: Re: [PATCH v3] mailbox: pcc: Support HW-Reduced Communication Subspace type 2 To: Jassi Brar , "Rafael J. Wysocki" Cc: Ashwin Chaugule , Robert Moore , Alexey Klimov , lkml , linux acpi , Loc Ho , Duc Dang , "Prakash, Prashanth" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jassi and Rafael, On Wed, Jun 15, 2016 at 9:19 AM, Prakash, Prashanth wrote: > > > On 6/9/2016 4:43 PM, Hoan Tran wrote: >> Hi Prashanth, >> >> On Thu, Jun 9, 2016 at 3:25 PM, Prakash, Prashanth >> wrote: >>> >>> On 6/9/2016 2:47 PM, Hoan Tran wrote: >>>> Hi Ashwin and Prashanth, >>>> >>>> On Wed, Jun 8, 2016 at 5:41 PM, Hoan Tran wrote: >>>>> Hi Prashanth, >>>>> >>>>> >>>>> On Wed, Jun 8, 2016 at 5:32 PM, Prakash, Prashanth >>>>> wrote: >>>>>> On 6/8/2016 10:24 AM, Hoan Tran wrote: >>>>>>> Hi Ashwin, >>>>>>> >>>>>>> On Wed, Jun 8, 2016 at 5:18 AM, Ashwin Chaugule >>>>>>> wrote: >>>>>>>> + Prashanth (Can you please have a look as well?) >>>>>>>> >>>>>>>> On 31 May 2016 at 15:35, Hoan Tran wrote: >>>>>>>>> Hi Ashwin, >>>>>>>> Hi, >>>>>>>> >>>>>>>> Sorry about the delay. I'm in the middle of switching jobs and >>>>>>>> locations, so its been a bit crazy lately. >>>>>>> It's ok and hope you're doing well. >>>>>>> >>>>>>>> I dont have any major >>>>>>>> concerns with this code, although there could be subtle issues with >>>>>>>> this IRQ thing. In this patchset, your intent is to add support for >>>>>>>> PCC subspace type 2. But you're also adding support for tx command >>>>>>>> completion which is not specific to Type 2. We could support that even >>>>>>>> in Type 1. Hence I wanted to separate the two, not just for review, >>>>>>>> but also the async IRQ completion has subtle issues esp. in the case >>>>>>>> of async platform notification, where you could have a PCC client in >>>>>>>> the OS writing to the cmd bit and the platform sending an async >>>>>>>> notification by writing to some bits in the same 8byte address as the >>>>>>>> cmd bit. So we need some mutual exclusivity there, otherwise the OS >>>>>>>> and platform could step on each other. Perhaps Prashanth has better >>>>>>>> insight into this. >>>>>>> I think, this mutual exclusivity could be in another patch. >>>>>> Ashwin, >>>>>> Sorry, I am not sure how we can prevent platform and OSPM from stepping on >>>>>> each other. There is a line is spec that says "all operations on status field >>>>>> must be made using interlocked operations", but not sure what these >>>>>> interlocked operation translates to. >>>>> Yes, I had the same question about how to prevent it. >>>> For platform notification, if the hardware doesn't support interlocked >>>> operations. I think we can use a workaround that, platform triggers >>>> interrupt to OSPM without touching status field. The OSPM PCC client >>>> will decide what to do with this interrupt. For example, OSPM sends a >>>> consumer command to check it. >>> How do we decide which platform can support this interlocked operation? >>> and how do we decide between a completion notification and platform >>> notification? >> Truly, we should follow the specification. But I don't know if there's >> any hardware support this interlocked operation. >> For the decide between a completion notification and platform notification >> - Completion notification: Bit "Command Complete" is set. >> - Platform notification: Bit "Command Complete" is not set. >> >>> I think the ACPI spec on platform notification is quite ambiguous and it is >>> best to get the necessary clarification and/or correction before implementing >>> anything related to platform notification. >> Agreed, a clarification inside ACPI Specification is needed > This patch look good to me, as it doesn't deal with platform notification. > We can try to get some clarification from spec side before handling the platform > notification pieces. > > Reviewed-by: Prashanth Prakash Do you have plan to apply this patch ? Thanks Hoan > > Thanks, > Prashanth > -- > To unsubscribe from this list: send the line "unsubscribe linux-acpi" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html