[RFC,13/13] scsi: megaraid: Make use of dev_64bit_mmio_supported()
diff mbox series

Message ID 20210226140305.26356-14-nsaenzjulienne@suse.de
State New, archived
Headers show
Series
  • Generic way of dealing with broken 64-bit buses
Related show

Commit Message

Nicolas Saenz Julienne Feb. 26, 2021, 2:03 p.m. UTC
Instead of relying on defines use dev_64bit_mmio_supported(), which
provides the same functionality. On top of that convert the
implementation to lo_hi_writeq(), for a cleaner end result.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
---
 drivers/scsi/megaraid/megaraid_sas_fusion.c | 23 ++++++++++-----------
 1 file changed, 11 insertions(+), 12 deletions(-)

Comments

Arnd Bergmann Feb. 26, 2021, 2:30 p.m. UTC | #1
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
Arnd Bergmann Feb. 26, 2021, 6:06 p.m. UTC | #2
On Fri, Feb 26, 2021 at 3:30 PM Arnd Bergmann <arnd@kernel.org> wrote:
>
> 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).

On second look, it seems your patch breaks the byteorder logic,
rather than fixing it. It would seem better to leave it unchanged
then, or to send a separate rework of the endianness conversion if
you think it is wrong.

       Arnd

Patch
diff mbox series

diff --git a/drivers/scsi/megaraid/megaraid_sas_fusion.c b/drivers/scsi/megaraid/megaraid_sas_fusion.c
index 38fc9467c625..d4933a591330 100644
--- a/drivers/scsi/megaraid/megaraid_sas_fusion.c
+++ b/drivers/scsi/megaraid/megaraid_sas_fusion.c
@@ -36,6 +36,7 @@ 
 #include <linux/vmalloc.h>
 #include <linux/workqueue.h>
 #include <linux/irq_poll.h>
+#include <linux/io-64-nonatomic-lo-hi.h>
 
 #include <scsi/scsi.h>
 #include <scsi/scsi_cmnd.h>
@@ -259,19 +260,17 @@  static void
 megasas_write_64bit_req_desc(struct megasas_instance *instance,
 		union MEGASAS_REQUEST_DESCRIPTOR_UNION *req_desc)
 {
-#if defined(writeq) && defined(CONFIG_64BIT)
-	u64 req_data = (((u64)le32_to_cpu(req_desc->u.high) << 32) |
-		le32_to_cpu(req_desc->u.low));
-	writeq(req_data, &instance->reg_set->inbound_low_queue_port);
-#else
+	u64 req_data = ((u64)le32_to_cpu(req_desc->u.high) << 32) |
+		       le32_to_cpu(req_desc->u.low);
 	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);
-#endif
+
+	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);
+	}
 }
 
 /**