Re: [RFC 13/13] scsi: megaraid: Make use of dev_64bit_mmio_supported()

From: Arnd Bergmann <arnd@kernel.org>
To: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc: Linux ARM <linux-arm-kernel@lists.infradead.org>,
	DTML <devicetree@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Rob Herring <robh+dt@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	Neil Armstrong <narmstrong@baylibre.com>,
	David Woodhouse <dwmw2@infradead.org>,
	Russell King - ARM Linux <linux@armlinux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Arnd Bergmann <arnd@arndb.de>, Will Deacon <will@kernel.org>
Subject: Re: [RFC 13/13] scsi: megaraid: Make use of dev_64bit_mmio_supported()
Date: Fri, 26 Feb 2021 15:30:45 +0100	[thread overview]
Message-ID: <CAK8P3a1cDgSo7LTtBZpzBo3xu23_uDEux8=15Xyw6JTpXtGqhw@mail.gmail.com> (raw)
In-Reply-To: <20210226140305.26356-14-nsaenzjulienne@suse.de>

On Fri, Feb 26, 2021 at 3:03 PM Nicolas Saenz Julienne
<nsaenzjulienne@suse.de> wrote:

>         unsigned long flags;
> -       spin_lock_irqsave(&instance->hba_lock, flags);
> -       writel(le32_to_cpu(req_desc->u.low),
> -               &instance->reg_set->inbound_low_queue_port);
> -       writel(le32_to_cpu(req_desc->u.high),
> -               &instance->reg_set->inbound_high_queue_port);
> -       spin_unlock_irqrestore(&instance->hba_lock, flags);

> +
> +       if (dev_64bit_mmio_supported(&instance->pdev->dev)) {
> +               writeq(req_data, &instance->reg_set->inbound_low_queue_port);
> +       } else {
> +               spin_lock_irqsave(&instance->hba_lock, flags);
> +               lo_hi_writeq(req_data, &instance->reg_set->inbound_low_queue_port);
> +               spin_unlock_irqrestore(&instance->hba_lock, flags);
> +       }

I see your patch changes the code to the lo_hi_writeq() accessor,
and it also fixes the endianness bug (double byteswap on big-endian),
but it does not fix the spinlock bug (writel on pci leaks out of the lock
unless it's followed by a read).

I'd suggest splitting the bugfix from the cleanup here, and fixing both
of the bugs while you're at it.

      Arnd