From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vinod Koul Date: Mon, 16 Jul 2012 11:24:59 +0000 Subject: Re: [PATCH 5/7 v2] dma: sh: use an integer slave ID to improve API compatibility Message-Id: <1342437179.1726.61.camel@vkoul-udesk3> List-Id: References: <1341484183-10757-1-git-send-email-g.liakhovetski@gmx.de> <1341484183-10757-6-git-send-email-g.liakhovetski@gmx.de> <1342418828.1726.37.camel@vkoul-udesk3> <1342421587.1726.49.camel@vkoul-udesk3> <1342427305.1726.50.camel@vkoul-udesk3> <1342431452.1726.54.camel@vkoul-udesk3> <1342434256.1726.57.camel@vkoul-udesk3> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Guennadi Liakhovetski Cc: Magnus Damm , linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org On Mon, 2012-07-16 at 12:55 +0200, Guennadi Liakhovetski wrote: > On Mon, 16 Jul 2012, Vinod Koul wrote: > > > On Mon, 2012-07-16 at 12:01 +0200, Guennadi Liakhovetski wrote: > > > On Mon, 16 Jul 2012, Vinod Koul wrote: > > > > > > > On Mon, 2012-07-16 at 10:47 +0200, Guennadi Liakhovetski wrote: > > > > > > I want to know what does ccr and mid_rid mean to dmac here? > > > > > > > > > > CHCR contains a few fields, some enable various interrupt sources, some > > > > > specify repeat- and renew-modes, others yet specify transfer size, source > > > > > and destination address-modes (incrementing, constant, decrementing), > > > > > others yet select a DMA client category (slave / memcpy / ...), and a > > > > > transfer flag. Some of these fields could be calculated, others are > > > > > pre-defined for various slaves, the exact layout of those fields can also > > > > > vary between SoCs. > > > > I do not understand how clients would provide these values. > > > > For pre-defined values, they should be dmac property why should client > > > > like spi or mmc have clue about it? > > > > > > > > For others like you mentioned, i guess they could be easily calculated, > > > > right? > > > > > > > > > MID_RID is actually a slave-selector, it contains a magic value, that > > > > > cannot be calculated. > > > > and again, how does client know this? > > > > > > I might be misunderstanding you, but from earlier discussions I got an > > > impression, that the DMAC should know nothing about clients, i.e., should > > > receive no client-specific information from its platform data. Instead > > > clients should provide it when configuring the channel. If this is > > > correct, then the preferred way would be to specify these values in client > > > platform data and then pass it to the DMAC with slave-config calls? Or > > > have I misunderstood you and this per-client information should be kept in > > > DMAC platform data? > > You haven't misunderstood me. dmacs should not know of client data and > > should be client agnostic. > > > > BUT, are these parameters ccr and mid_rid client data, i do not think > > so, they seem to be dmac controller parameters which you need to > > configure channel or is that not the case. If not why bother passing > > them to dmac? > > Yes, that's right - these values have to be written to DMAC channel > configuration registers, so, we do not have to change anything, those > values can remain DMAC parameters and be passed to it directly from > platform data. Can you get that in future fixes. > > > Either way something looks fishy to me. > > You can always tell me what you don't like about the driver, but I don't > see why this specific patch should cause any problem - it only changes the > type of the slave-id variable from unsigned to signed to be able to pass > negative error values in it too. This question was not specific to this patchset Btw I am quite happy with this patchset. Good direction for this and thanks for taking it up. -- ~Vinod From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753118Ab2GPLNN (ORCPT ); Mon, 16 Jul 2012 07:13:13 -0400 Received: from mga03.intel.com ([143.182.124.21]:11865 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751476Ab2GPLNK (ORCPT ); Mon, 16 Jul 2012 07:13:10 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.71,315,1320652800"; d="scan'208";a="122965819" Subject: Re: [PATCH 5/7 v2] dma: sh: use an integer slave ID to improve API compatibility From: Vinod Koul To: Guennadi Liakhovetski Cc: Magnus Damm , linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: References: <1341484183-10757-1-git-send-email-g.liakhovetski@gmx.de> <1341484183-10757-6-git-send-email-g.liakhovetski@gmx.de> <1342418828.1726.37.camel@vkoul-udesk3> <1342421587.1726.49.camel@vkoul-udesk3> <1342427305.1726.50.camel@vkoul-udesk3> <1342431452.1726.54.camel@vkoul-udesk3> <1342434256.1726.57.camel@vkoul-udesk3> Content-Type: text/plain; charset="UTF-8" Date: Mon, 16 Jul 2012 16:42:59 +0530 Message-ID: <1342437179.1726.61.camel@vkoul-udesk3> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2012-07-16 at 12:55 +0200, Guennadi Liakhovetski wrote: > On Mon, 16 Jul 2012, Vinod Koul wrote: > > > On Mon, 2012-07-16 at 12:01 +0200, Guennadi Liakhovetski wrote: > > > On Mon, 16 Jul 2012, Vinod Koul wrote: > > > > > > > On Mon, 2012-07-16 at 10:47 +0200, Guennadi Liakhovetski wrote: > > > > > > I want to know what does ccr and mid_rid mean to dmac here? > > > > > > > > > > CHCR contains a few fields, some enable various interrupt sources, some > > > > > specify repeat- and renew-modes, others yet specify transfer size, source > > > > > and destination address-modes (incrementing, constant, decrementing), > > > > > others yet select a DMA client category (slave / memcpy / ...), and a > > > > > transfer flag. Some of these fields could be calculated, others are > > > > > pre-defined for various slaves, the exact layout of those fields can also > > > > > vary between SoCs. > > > > I do not understand how clients would provide these values. > > > > For pre-defined values, they should be dmac property why should client > > > > like spi or mmc have clue about it? > > > > > > > > For others like you mentioned, i guess they could be easily calculated, > > > > right? > > > > > > > > > MID_RID is actually a slave-selector, it contains a magic value, that > > > > > cannot be calculated. > > > > and again, how does client know this? > > > > > > I might be misunderstanding you, but from earlier discussions I got an > > > impression, that the DMAC should know nothing about clients, i.e., should > > > receive no client-specific information from its platform data. Instead > > > clients should provide it when configuring the channel. If this is > > > correct, then the preferred way would be to specify these values in client > > > platform data and then pass it to the DMAC with slave-config calls? Or > > > have I misunderstood you and this per-client information should be kept in > > > DMAC platform data? > > You haven't misunderstood me. dmacs should not know of client data and > > should be client agnostic. > > > > BUT, are these parameters ccr and mid_rid client data, i do not think > > so, they seem to be dmac controller parameters which you need to > > configure channel or is that not the case. If not why bother passing > > them to dmac? > > Yes, that's right - these values have to be written to DMAC channel > configuration registers, so, we do not have to change anything, those > values can remain DMAC parameters and be passed to it directly from > platform data. Can you get that in future fixes. > > > Either way something looks fishy to me. > > You can always tell me what you don't like about the driver, but I don't > see why this specific patch should cause any problem - it only changes the > type of the slave-id variable from unsigned to signed to be able to pass > negative error values in it too. This question was not specific to this patchset Btw I am quite happy with this patchset. Good direction for this and thanks for taking it up. -- ~Vinod