Re: [PATCH 1/2] ux500: Adding support for u8500 Hsem functionalityV2

From: Mathieu Poirier
Date: Tue Apr 12 2011 - 15:13:27 EST

On 11-04-12 11:46 AM, Arnd Bergmann wrote:
On Monday 11 April 2011, mathieu.poirier@xxxxxxxxxx wrote:
From: Mathieu J. Poirier<mathieu.poirier@xxxxxxxxxx>

This is the second spin on STE's Hsem driver that is implemented
through the hwspinlock scheme. More specifically:

More comments have been added in the code.
Cleanup of included header files.
One of the original contributor's name corrected.
Calls to 'pm_runtime_disable'restored.

Signed-off-by: Mathieu Poirier<mathieu.poirier@xxxxxxxxxx>
Looks very nice overall, just a few small details I noticed:

+#define HSEM_CTRL_REG 0x00
+#define HSEM_ICRALL 0x90
+#define HSEM_PROTOCOL_1 0x01
+#define to_u8500_hsem(lock) \
+ container_of(lock, struct u8500_hsem, lock)
+struct u8500_hsem {
+ struct hwspinlock lock;
+ void __iomem *addr;
It seems inconsistent to name it sem instead of spinlock.

This is a good point and I've been going back and forth on that one. TI's implementation is based on 'spinlock' but in this case there is not a single mention of a 'spinlock' in the CPU's reference manual, leaving potential users to wonder if spinlock == hsem. I think using 'hsem' makes more sense here.
+struct u8500_hsem_state {
+ void __iomem *io_base; /* Mapped base address */
If you make that one data structure, you only need a single allocation:

struct u8500_hsem_state {
void __iomem *io_base;
struct u8500_hsem hsem[U8500_MAX_SEMAPHORE];
I don't see the real advantage in doing a single allocation - the dynamic allocation method is also used in 'omap_hwspinlock.c'. Is modification mandatory to get the driver accepted ?
+ for (i = 0; i< U8500_MAX_SEMAPHORE; i++) {
+ u8500_lock = kzalloc(sizeof(*u8500_lock), GFP_KERNEL);
+ if (!u8500_lock) {
+ ret = -ENOMEM;
+ goto free_locks;
+ }
+ u8500_lock-> =&pdev->dev;
+ u8500_lock->lock.owner = THIS_MODULE;
+ u8500_lock-> = i;
+ u8500_lock->lock.ops =&u8500_hwspinlock_ops;
+ u8500_lock->addr = io_base + offset + sizeof(u32) * i;
+ ret = hwspin_lock_register(&u8500_lock->lock);
+ if (ret) {
+ kfree(u8500_lock);
+ goto free_locks;
+ }
+ }
When you do that, this can be a single allocation.
If you don't mind, I will let Ohad and friends deal with the API improvement.

Thinking about it some more, it may actually be worthwhile to still improve
the API here: I think the owner field should be part of the operations structure,
because it is constant. It would also be nice to have a "private" pointer
in struct hwspinlock, so you don't need to wrap it if you don't want to.

Finally, the hwspin_lock_register could take the specific values as arguments
instead of requiring you to fill it out first.


Thanks for the review,

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