From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: Lian Minghuan-B31939 <B31939@freescale.com>,
"Minghuan.Lian@freescale.com" <Minghuan.Lian@freescale.com>,
"Mingkai.Hu@freescale.com" <Mingkai.Hu@freescale.com>,
Roy Zang <tie-fei.zang@freescale.com>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>
Subject: Re: 答复: [PATCH 2/2] PCI: Layerscape: Add Layerscape PCIe driver
Date: Tue, 09 Sep 2014 13:58:17 +0200 [thread overview]
Message-ID: <10318509.zOTEUpfc9B@wuerfel> (raw)
In-Reply-To: <540F51F1.1060909@freescale.com>
On Tuesday 09 September 2014 19:16:01 Lian Minghuan-B31939 wrote:
> On 2014年09月09日 10:50, Arnd Bergmann wrote:
> > 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.
>
> [Minghuan] I have added MSI support for LS1021A PCIe just reserved 31
> interrupts as used.
I don't understand your logic then. If LS1021A has an incorrect MSI
implementation, and you may want to reuse the PCIe driver with a
future chip that either includes a correct MSI implementation, or
with one that uses the GICv3 instead, isn't that even more reason
to split out the MSI support into a separate driver?
That way you can at least separate the normal code path from the
broken one and don't need any special run-time or compile-conditionals
beyond calling of_pci_find_msi_chip_by_node().
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: 答复: [PATCH 2/2] PCI: Layerscape: Add Layerscape PCIe driver
Date: Tue, 09 Sep 2014 13:58:17 +0200 [thread overview]
Message-ID: <10318509.zOTEUpfc9B@wuerfel> (raw)
In-Reply-To: <540F51F1.1060909@freescale.com>
On Tuesday 09 September 2014 19:16:01 Lian Minghuan-B31939 wrote:
> On 2014?09?09? 10:50, Arnd Bergmann wrote:
> > On Tuesday 09 September 2014 18:46:59 Lian Minghuan-B31939 wrote:
> >> On 2014?09?09? 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.
>
> [Minghuan] I have added MSI support for LS1021A PCIe just reserved 31
> interrupts as used.
I don't understand your logic then. If LS1021A has an incorrect MSI
implementation, and you may want to reuse the PCIe driver with a
future chip that either includes a correct MSI implementation, or
with one that uses the GICv3 instead, isn't that even more reason
to split out the MSI support into a separate driver?
That way you can at least separate the normal code path from the
broken one and don't need any special run-time or compile-conditionals
beyond calling of_pci_find_msi_chip_by_node().
Arnd
next prev parent reply other threads:[~2014-09-09 11:58 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-04 18:45 [PATCH 1/2] PCI: designware: change MSI-related pcie_host_ops Minghuan Lian
2014-09-04 18:45 ` Minghuan Lian
2014-09-04 13:20 ` Bjorn Helgaas
2014-09-04 13:20 ` Bjorn Helgaas
2014-09-05 6:15 ` 答复: " Minghuan.Lian at freescale.com
2014-09-04 18:45 ` [PATCH 2/2] PCI: Layerscape: Add Layerscape PCIe driver Minghuan Lian
2014-09-04 18:45 ` Minghuan Lian
2014-09-04 12:14 ` Arnd Bergmann
2014-09-04 12:14 ` Arnd Bergmann
2014-09-04 13:51 ` Arnd Bergmann
2014-09-04 13:51 ` Arnd Bergmann
2014-09-04 13:57 ` Arnd Bergmann
2014-09-04 13:57 ` Arnd Bergmann
2014-09-05 7:22 ` 答复: " Minghuan.Lian at freescale.com
2014-09-05 8:44 ` Arnd Bergmann
2014-09-05 8:44 ` Arnd Bergmann
2014-09-09 17:25 ` Lian Minghuan-B31939
2014-09-09 17:25 ` Lian Minghuan-B31939
2014-09-09 9:56 ` Arnd Bergmann
2014-09-09 9:56 ` Arnd Bergmann
2014-09-09 18:46 ` Lian Minghuan-B31939
2014-09-09 18:46 ` Lian Minghuan-B31939
2014-09-09 10:50 ` Arnd Bergmann
2014-09-09 10:50 ` Arnd Bergmann
2014-09-09 19:16 ` Lian Minghuan-B31939
2014-09-09 19:16 ` Lian Minghuan-B31939
2014-09-09 11:58 ` Arnd Bergmann [this message]
2014-09-09 11:58 ` Arnd Bergmann
2014-09-10 11:29 ` Lian Minghuan-B31939
2014-09-10 11:29 ` Lian Minghuan-B31939
2014-09-04 13:24 ` Bjorn Helgaas
2014-09-04 13:24 ` Bjorn Helgaas
2014-09-05 7:24 ` 答复: " Minghuan.Lian at freescale.com
2014-09-04 20:21 ` Fabio Estevam
2014-09-04 20:21 ` Fabio Estevam
2014-09-04 21:12 ` Arnd Bergmann
2014-09-04 21:12 ` Arnd Bergmann
2014-09-05 6:43 ` 答复: " Minghuan.Lian at freescale.com
2014-09-05 7:40 ` Minghuan.Lian at freescale.com
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