On 3/17/2018 12:03 AM, Sinan Kaya wrote:

quoted

On 3/16/2018 11:40 PM, Sinan Kaya wrote:

quoted

I'll change writel_relaxed() with __raw_writel() in the series like you

suggested

quoted

quoted

and also look at your other comments.

I spoke too soon.

Now that I realized, code needs to follow one of the following patterns

for correctness

quoted

1)
wmb()
writel()/writel_relaxed()

or

2)
wmb()
__raw_wrltel()
mmiowb()

but definitely not

wmb()
__raw_wrltel()

Since #1 == #2, I'll stick to my current implementation of writel_relaxed()

Changing writel() to writel_relaxed() or __raw_writel() isn't enough.

PowerPC needs mmiowb()

quoted

for correctness. ARM's mmiowb() implementation is empty.

So, there is no one size fits all solution with the current state of affairs.

I think I finally got what you mean.

Code seems to have

wmb()
writel()/writeq()
wmb()

this can be safely replaced with

wmb()
__raw_writel()/__raw_writeq()
wmb()

This will work on all arches. Below is the new version. Let me know if this is
OK.

+++ b/drivers/infiniband/hw/cxgb4/t4.h

@@ -457,7 +457,7 @@ static inline void pio_copy(u64 __iomem *dst, u64

*src)
        int count = 8;

        while (count) {
-               writeq(*src, dst);
+               __raw_writeq(*src, dst);
                src++;
                dst++;
                count--;

@@ -477,15 +477,16 @@ static inline void t4_ring_sq_db(struct t4_wq *wq,

u16 inc, union t4_wr *wqe)
                                 (u64 *)wqe);
                } else {
                        pr_debug("DB wq->sq.pidx = %d\n", wq->sq.pidx);
-                       writel(PIDX_T5_V(inc) | QID_V(wq->sq.bar2_qid),
-                              wq->sq.bar2_va + SGE_UDB_KDOORBELL);
+                       __raw_writel(PIDX_T5_V(inc) | QID_V(wq->sq.bar2_qid),
+                                    wq->sq.bar2_va + SGE_UDB_KDOORBELL);
                }

                /* Flush user doorbell area writes. */
                wmb();
                return;
        }
-       writel(QID_V(wq->sq.qid) | PIDX_V(inc), wq->db);
+       __raw_writel(QID_V(wq->sq.qid) | PIDX_V(inc), wq->db);
+       mmiowmb()
 }

 static inline void t4_ring_rq_db(struct t4_wq *wq, u16 inc,

@@ -502,15 +503,16 @@ static inline void t4_ring_rq_db(struct t4_wq *wq,

u16 inc,
                                 (void *)wqe);
                } else {
                        pr_debug("DB wq->rq.pidx = %d\n", wq->rq.pidx);
-                       writel(PIDX_T5_V(inc) | QID_V(wq->rq.bar2_qid),
-                              wq->rq.bar2_va + SGE_UDB_KDOORBELL);
+                       __raw_writel(PIDX_T5_V(inc) | QID_V(wq->rq.bar2_qid),
+                                    wq->rq.bar2_va + SGE_UDB_KDOORBELL);
                }

                /* Flush user doorbell area writes. */
                wmb();
                return;
        }
-       writel(QID_V(wq->rq.qid) | PIDX_V(inc), wq->db);
+       __raw_writel(QID_V(wq->rq.qid) | PIDX_V(inc), wq->db);
+       mmiowmb();
 }