Messages in this thread | | | Date | Thu, 08 Sep 2022 15:51:30 +0100 | From | Marc Zyngier <> | Subject | Re: [EXT] Re: [PATCH v9 2/4] irqchip: Add IMX MU MSI controller driver |
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On Thu, 08 Sep 2022 15:23:53 +0100, Frank Li <frank.li@nxp.com> wrote: > > > > > On Wed, 07 Sep 2022 04:48:54 +0100, > > Frank Li <Frank.Li@nxp.com> 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?
> > > + > > > +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.
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