Messages in this thread | | | From | Arnd Bergmann <> | Date | Thu, 31 Mar 2022 17:44:55 +0200 | Subject | Re: [PATCH v3 1/1] soc: fujitsu: Add A64FX diagnostic interrupt driver |
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On Thu, Mar 31, 2022 at 1:49 PM Greg KH <gregkh@linuxfoundation.org> wrote: > > + > > +static irqreturn_t a64fx_diag_handler(int irq, void *dev_id) > > +{ > > + handle_sysrq('c'); > > > Why is this calling this sysrq call? From an interrupt? Why? > > And you are hard-coding "c", are you sure?
This is an actual sysrq driver in the traditional sense, where you can send a single interrupt to the machine from the outside over a side channel.
I suggested sysrq instead of just panic() to make it a bit more flexible. Unfortunately there is no additional data, so it comes down to always sending the same character.
It would be possible to make that character configurable with a module parameter or something like that, but I'm not sure that is an improvement. Maybe you have another idea for this.
> > +static void a64fx_diag_interrupt_clear(struct a64fx_diag_priv *priv) > > +{ > > + u32 mmsc; > > + const void __iomem *diag_status_reg_addr; > > + > > + diag_status_reg_addr = priv->mmsc_reg_base + BMC_DIAG_INTERRUPT_STATUS_OFFSET; > > + mmsc = readl(diag_status_reg_addr); > > + if (mmsc & BMC_INTERRUPT_STATUS_MASK) > > + writel(BMC_INTERRUPT_STATUS_MASK, (void *)diag_status_reg_addr); > > No need to wait for the write to complete? > > You shouldn't have to cast diag_status_reg_addr, right?
I think the cast is needed because the declaration of 'diag_status_reg_addr' incorrectly marks it as 'const'. However, this should still trigger a 'make C=1' warning with sparse because it is now missing the __iomem annotation.
The correct solution of course is to remove both the cast and the 'const'.
Arnd
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