Messages in this thread | | | Subject | Re: [PATCH v2 2/2] parisc: define stronger ordering for the default readX() | From | Sinan Kaya <> | Date | Tue, 17 Apr 2018 10:13:28 -0400 |
| |
Hi James,
> > Perhaps if you gave an example of the actual problem you're trying to > fix we could assess if it affects parisc.
Let me clarify myself here. Maybe, there is a better solution.
/* assign ownership */ desc->status = DEVICE_OWN;
/* notify device of new descriptors */ writel(DESC_NOTIFY, doorbell);
The difference between writel() and writel_relax() is writel() guarantees memory transactions to be flushed to the device before the register write. writel_relaxed() does not provide any guarantees about the memory and IO operations.
Similarly, readl() provides following code to observe the DMA result while readl_relaxed() does not provide this guarantee.
Ideally, you want to embed rmb() and wmb() into the writel() and readl() to provide this guarantee.
PA-RISC doesn't seem to support neither one of the barrier types. If you are familiar with the architecture, maybe you could guide us here.
Is __raw_writeX() enough to provide this guarantee for this architecture?
Sinan
-- Sinan Kaya Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
| |