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

On Fri, Feb 26, 2021 at 3:03 PM Nicolas Saenz Julienne
[off-list ref] 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