Messages in this thread | | | From | Arnd Bergmann <> | Date | Thu, 23 Jan 2020 12:39:06 +0100 | Subject | Re: [PATCH 05/16] bus: mhi: core: Add support for ringing channel/event ring doorbells |
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On Thu, Jan 23, 2020 at 12:19 PM Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> wrote:
> +int __must_check mhi_read_reg(struct mhi_controller *mhi_cntrl, > + void __iomem *base, u32 offset, u32 *out) > +{ > + u32 tmp = readl_relaxed(base + offset); .... > +void mhi_write_reg(struct mhi_controller *mhi_cntrl, void __iomem *base, > + u32 offset, u32 val) > +{ > + writel_relaxed(val, base + offset);
Please avoid using _relaxed accessors by default, and use the regular ones instead. There are a number of things that can go wrong with the relaxed version, so ideally each caller should have a comment explaining why this instance is safe without the barriers and why it matters to not have it.
If there are performance critical callers of mhi_read_reg/mhi_write_reg, you could add mhi_read_reg_relaxed/mhi_write_reg_relaxed for those and apply the same rules there.
Usually most mmio accesses are only needed for reconfiguration or other slow paths.
Arnd
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