From: Douglas Anderson <diand...@chromium.org> commit 4079d35fa4fca4ee0ffd66968312fc86a5e8c290 upstream.
When the Qualcomm pinctrl driver wants to Ack an interrupt, it does a read-modify-write on the interrupt status register. On some SoCs it makes sure that the status bit is 1 to "Ack" and on others it makes sure that the bit is 0 to "Ack". Presumably the first type of interrupt controller is a "write 1 to clear" type register and the second just let you directly set the interrupt status register. As far as I can tell from scanning structure definitions, the interrupt status bit is always in a register by itself. Thus with both types of interrupt controllers it is safe to "Ack" interrupts without doing a read-modify-write. We can do a simple write. It should be noted that if the interrupt status bit _was_ ever in a register with other things (like maybe status bits for other GPIOs): a) For "write 1 clear" type controllers then read-modify-write would be totally wrong because we'd accidentally end up clearing interrupts we weren't looking at. b) For "direct set" type controllers then read-modify-write would also be wrong because someone setting one of the other bits in the register might accidentally clear (or set) our interrupt. I say this simply to show that the current read-modify-write doesn't provide any sort of "future proofing" of the code. In fact (for "write 1 clear" controllers) the new code is slightly more "future proof" since it would allow more than one interrupt status bits to share a register. NOTE: this code fixes no bugs--it simply avoids an extra register read. Signed-off-by: Douglas Anderson <diand...@chromium.org> Reviewed-by: Maulik Shah <mks...@codeaurora.org> Tested-by: Maulik Shah <mks...@codeaurora.org> Reviewed-by: Stephen Boyd <swb...@chromium.org> Reviewed-by: Bjorn Andersson <bjorn.anders...@linaro.org> Link: https://lore.kernel.org/r/20210114191601.v7.2.I3635de080604e1feda770591c5563bd6e63dd39d@changeid Signed-off-by: Linus Walleij <linus.wall...@linaro.org> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- drivers/pinctrl/qcom/pinctrl-msm.c | 23 ++++++++--------------- 1 file changed, 8 insertions(+), 15 deletions(-) --- a/drivers/pinctrl/qcom/pinctrl-msm.c +++ b/drivers/pinctrl/qcom/pinctrl-msm.c @@ -791,16 +791,13 @@ static void msm_gpio_irq_clear_unmask(st raw_spin_lock_irqsave(&pctrl->lock, flags); - if (status_clear) { - /* - * clear the interrupt status bit before unmask to avoid - * any erroneous interrupts that would have got latched - * when the interrupt is not in use. - */ - val = msm_readl_intr_status(pctrl, g); - val &= ~BIT(g->intr_status_bit); - msm_writel_intr_status(val, pctrl, g); - } + /* + * clear the interrupt status bit before unmask to avoid + * any erroneous interrupts that would have got latched + * when the interrupt is not in use. + */ + if (status_clear) + msm_writel_intr_status(0, pctrl, g); val = msm_readl_intr_cfg(pctrl, g); val |= BIT(g->intr_raw_status_bit); @@ -905,11 +902,7 @@ static void msm_gpio_irq_ack(struct irq_ raw_spin_lock_irqsave(&pctrl->lock, flags); - val = msm_readl_intr_status(pctrl, g); - if (g->intr_ack_high) - val |= BIT(g->intr_status_bit); - else - val &= ~BIT(g->intr_status_bit); + val = g->intr_ack_high ? BIT(g->intr_status_bit) : 0; msm_writel_intr_status(val, pctrl, g); if (test_bit(d->hwirq, pctrl->dual_edge_irqs))
