why iowrite32_rep() doesn't work, I have to use the iowrite32() with a loop

ayaka ayaka at soulik.info
Thu Nov 16 15:12:24 EST 2017

Hello All:

   I am writing a driver, I need to write a series of values into the 
registers. The old code use the writel_relaxed() to avoid flushing cache 
between echo of register. I want to use the recommended way of the io 
operations, so I choose the iowrite32()_req(), but I found what it wrote 
nothing, I read it at once after a memory barrier, there is no contents 
there. But it I use the iowrite32() with a loop, it works well and the 
registers of the device is configured.  What make this problem?

The io memory is assigned with devm_ioremap_resource().

void mpp_dev_write_seq(struct rockchip_mpp_dev *mpp_dev, unsigned long 
                        void *buffer, unsigned long count)
         int i;
#if 1
         for (i = 0; i < count; i++) {
                 u32 *cur = (u32 *)buffer;
                 u32 pos = offset + i * 4;

                 cur += i;
                 mpp_debug(DEBUG_SET_REG, "write reg[%03d]: %08x\n", 
pos, *cur);
                 iowrite32(*cur, mpp_dev->reg_base + pos);
         iowrite32_rep(mpp_dev->reg_base + offset, buffer, count);
         for (i = 0; i < count; i++) {
                 u32 cur = 0;
                 u32 pos = offset / 4 + i;

                 cur = ioread32(mpp_dev->reg_base + pos * 4);
                 pr_info("get reg[%03d]: %08x\n", pos, cur);


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