From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [Linaro-acpi] [PATCH v3 1/3] Mailbox: Add support for PCC mailbox and channels Date: Wed, 03 Sep 2014 13:23:21 +0200 Message-ID: <5594980.1z2dWMD9C4@wuerfel> References: <1409081738-5602-1-git-send-email-ashwin.chaugule@linaro.org> <2819816.9eneSBSqnQ@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: Received: from mout.kundenserver.de ([212.227.126.131]:50797 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932119AbaICLX2 (ORCPT ); Wed, 3 Sep 2014 07:23:28 -0400 In-Reply-To: Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: linaro-acpi@lists.linaro.org Cc: Ashwin Chaugule , linux acpi , Mark Brown , "Rafael J. Wysocki" On Tuesday 02 September 2014 16:15:05 Ashwin Chaugule wrote: > > > >> > The "index" in mbox_request_channel() picks > >> > up one set of strings. How should this work with PCC? Should we use > >> > the PCC client platform_device->dev->platform_data to store mailbox > >> > controller strings? > > > > I didn't think there was more than one PCC provider, why do you even > > need a string? > > > > For the general case in ACPI, there should be a similar way of looking > > up mailbox providers to what we have in DT, but if I understand you > > correctly, the PCC specification does not allow that. > > Right. At least not in a way DT does. PCC clients know if something > needs to be written/read via PCC mailbox and can identify a PCC > subspace. (i.e. Mailbox channel). The PCC mailbox is uniquely > identified/defined in the spec. > > #define ACPI_ADR_SPACE_PLATFORM_COMM (acpi_adr_space_type) 10 > > So we could use this ID instead of a string and use that to look up > the PCC controller for a PCC client. I didn't realize this was the case. Does that mean we can treat pcc as a linearly accessible address space the way we do for system memory, pci-config etc? If that works, we should probably just have a regmap for it rather than expose the mailbox API to client drivers. Arnd