linux-kernel - Re: [PATCH 1/2] PCI: mediatek-gen3: Stop acquiring spinlocks in {suspend,resume}

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Date:   Thu, 8 Jun 2023 12:15:07 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     ryder.lee@...iatek.com, jianjun.wang@...iatek.com,
        lpieralisi@...nel.org, kw@...ux.com, robh@...nel.org,
        bhelgaas@...gle.com, p.zabel@...gutronix.de,
        matthias.bgg@...il.com, linux-pci@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] PCI: mediatek-gen3: Stop acquiring spinlocks in
 {suspend,resume}_noirq

On Thu, May 04, 2023 at 01:35:08PM +0200, AngeloGioacchino Del Regno wrote:
> In mtk_pcie_suspend_noirq() and mtk_pcie_resume_noirq() we are,
> respectively, disabling and enabling generation of interrupts and
> then saving and restoring the enabled interrupts register: since
> we're using noirq PM callbacks, that can be safely done without
> holding any spin lock.

Tangent: it's annoying that pcie-mediatek.c and pcie-mediatek-gen3.c
use identical "mtk_pcie_suspend_noirq()" names.  That makes browsing
harder than it needs to be.  But I see that you refer to
mediatek-gen3.

> +++ b/drivers/pci/controller/pcie-mediatek-gen3.c
> @@ -963,8 +963,6 @@ static void mtk_pcie_irq_save(struct mtk_gen3_pcie *pcie)
>  {
>  	int i;
>  
> -	raw_spin_lock(&pcie->irq_lock);
> -
>  	pcie->saved_irq_state = readl_relaxed(pcie->base + PCIE_INT_ENABLE_REG);
>  
>  	for (i = 0; i < PCIE_MSI_SET_NUM; i++) {
> @@ -973,16 +971,12 @@ static void mtk_pcie_irq_save(struct mtk_gen3_pcie *pcie)
>  		msi_set->saved_irq_state = readl_relaxed(msi_set->base +
>  					   PCIE_MSI_SET_ENABLE_OFFSET);
>  	}
> -
> -	raw_spin_unlock(&pcie->irq_lock);
>  }

Jianjun added mtk_pcie_irq_save() and mtk_pcie_irq_restore() with
d537dc125f07 ("PCI: mediatek-gen3: Add system PM support").  

I suggest looking at other drivers and structuring mediatek-gen3
similarly, including using similar function names.  No other drivers
have a .*_pcie_irq_save() function.  Several have .*_pcie_host_init(),
and some of those do include some IRQ setup.

Bjorn