> -----Original Message----- > From: Marc Zyngier <maz@xxxxxxxxxx> > Sent: Thursday, September 8, 2022 9:52 AM > To: Frank Li <frank.li@xxxxxxx> > Cc: tglx@xxxxxxxxxxxxx; robh+dt@xxxxxxxxxx; > krzysztof.kozlowski+dt@xxxxxxxxxx; shawnguo@xxxxxxxxxx; > s.hauer@xxxxxxxxxxxxxx; kw@xxxxxxxxx; bhelgaas@xxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-arm- > kernel@xxxxxxxxxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx; Peng Fan > <peng.fan@xxxxxxx>; Aisheng Dong <aisheng.dong@xxxxxxx>; > jdmason@xxxxxxxx; kernel@xxxxxxxxxxxxxx; festevam@xxxxxxxxx; dl-linux- > imx <linux-imx@xxxxxxx>; kishon@xxxxxx; lorenzo.pieralisi@xxxxxxx; > ntb@xxxxxxxxxxxxxxx; lznuaa@xxxxxxxxx; imx@xxxxxxxxxxxxxxx; > manivannan.sadhasivam@xxxxxxxxxx > Subject: Re: [EXT] Re: [PATCH v9 2/4] irqchip: Add IMX MU MSI controller > driver > > Caution: EXT Email > > On Thu, 08 Sep 2022 15:23:53 +0100, > Frank Li <frank.li@xxxxxxx> wrote: > > > > > > > > On Wed, 07 Sep 2022 04:48:54 +0100, > > > Frank Li <Frank.Li@xxxxxxx> wrote: > > > > > > > > The MU block found in a number of Freescale/NXP SoCs supports > > > generating > > > > IRQs by writing data to a register > > > > > > > > This enables the MU block to be used as a MSI controller, by leveraging > > > > the platform-MSI API > > > > > > Missing full stop after each sentence. > > > > [Frank Li] Do you means missed "."? > > Yes. > > > > > diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig > > > > index 5e4e50122777d..e04c6521dce55 100644 > > > > --- a/drivers/irqchip/Kconfig > > > > +++ b/drivers/irqchip/Kconfig > > > > @@ -470,6 +470,15 @@ config IMX_INTMUX > > > > help > > > > Support for the i.MX INTMUX interrupt multiplexer. > > > > > > > > +config IMX_MU_MSI > > > > + bool "i.MX MU work as MSI controller" > > > > > > Why bool? Doesn't it also work as a module? > > > > [Frank Li] I remember you said that irq-chip can't be removed. > > So I am not sure why need build as module. > > Not being removed doesn't mean it cannot be built as a module and > loaded on demand. Why should I be forced to have this driver built-in > if my kernel is used on a variety of systems, only one of them having > this device? [Frank Li] A problem, platform_msi_create_irq_domain have NOT export to let module Call it. https://elixir.bootlin.com/linux/latest/source/drivers/base/platform-msi.c#L122 Do you want to me add EXPORT_SYMBOL_GPL for it OR keep "bool" here? > > > > > + > > > > +struct imx_mu_msi { > > > > + spinlock_t lock; > > > > + raw_spinlock_t reglock; > > > > > > Why two locks? Isn't one enough to protect both MSI allocation (which > > > happens once in a blue moon) and register access? > > > > [Frank Li] Previously your comment, ask me to use raw_spinlock for > > read\write register access. I don't think raw_spinlock is good for > > MSI allocation. > > Why wouldn't it be good enough? I'd really like to know. > > > > > > > > > Also, where are these locks initialised? > > > > > > > [Frank Li] struct imx_mu_msi is fill zero when allocated. > > Does it still need additional initialization for spinlock? > > Have you heard of lockdep? Or CONFIG_DEBUG_SPINLOCK? Maybe you > should > try it. > > > > > + if (!pdev) > > > > + return -ENODEV; > > > > > > How can that happen? > > > > > [Frank Li] Not sure, many driver check as it. > > And? Just because someone does something pointless, you have to > imitate them? > > M. > > -- > Without deviation from the norm, progress is not possible.
