From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.kundenserver.de ([212.227.17.10]:53930 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752626AbaIIKvB convert rfc822-to-8bit (ORCPT ); Tue, 9 Sep 2014 06:51:01 -0400 From: Arnd Bergmann To: Lian Minghuan-B31939 Cc: "Minghuan.Lian@freescale.com" , "linux-arm-kernel@lists.infradead.org" , "linux-pci@vger.kernel.org" , "Mingkai.Hu@freescale.com" , Roy Zang Subject: Re: =?UTF-8?B?562U5aSNOg==?= [PATCH 2/2] PCI: Layerscape: Add Layerscape PCIe driver Date: Tue, 09 Sep 2014 12:50:47 +0200 Message-ID: <60096763.M59cqLJ4gm@wuerfel> In-Reply-To: <540F4B23.5040209@freescale.com> References: <1409856338-1730-1-git-send-email-Minghuan.Lian@freescale.com> <6844751.zBSvS2zU47@wuerfel> <540F4B23.5040209@freescale.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Sender: linux-pci-owner@vger.kernel.org List-ID: On Tuesday 09 September 2014 18:46:59 Lian Minghuan-B31939 wrote: > On 2014年09月09日 09:56, Arnd Bergmann wrote: > > On Tuesday 09 September 2014 17:25:57 Lian Minghuan-B31939 wrote: > >> [Minghuan] I discussed with my colleague. They worry about performance > >> degradation if using regmap API, > >> because there are some fast device use scfg. We tend to use a simple way > >> to map andread/write scfg directly. > > > > I see. In this case, I would probably create a separate msi controller > > driver that owns the "fsl,ls1021a-scfg" device, and is referenced > > through the "msi-parent" property in the pcie controller. > > > > You can use of_pci_find_msi_chip_by_node() to get the msi_chip > > instance and then connect that to your pci host. This will also > > take care of the case where you may want to use the main GICv3 > > > on a future SoC. > [Minghuan] There is something wrong with LS1021A MSI hardware that it > only supports one interrupt not 32 interrupts. Now, I do not want to > create a separate msi controller driver just for incorrect hardware. > I may provide complete MSI driver for the new hardware when it is ready. Would you just leave out MSI support for the LS1021A PCIe variant? I guess that's fine because all device drivers should also support legacy interrupts and there is no performance gain in MSI in this case. Arnd