soc: qcom: rpmh-rsc: Don't use ktime for timeout in write_tcs_reg_sync()

The write_tcs_reg_sync() may be called after timekeeping is suspended
so it's not OK to use ktime.  The readl_poll_timeout_atomic() macro
implicitly uses ktime.  This was causing a warning at suspend time.

Change to just loop 1000000 times with a delay of 1 us between loops.
This may give a timeout of more than 1 second but never less and is
safe even if timekeeping is suspended.

NOTE: I don't have any actual evidence that we need to loop here.
It's possibly that all we really need to do is just read the value
back to ensure that the pipes are cleaned and the looping/comparing is
totally not needed.  I never saw the loop being needed in my tests.
However, the loop shouldn't hurt.

Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Reviewed-by: Maulik Shah <mkshah@codeaurora.org>
Fixes: 91160150aba0 ("soc: qcom: rpmh-rsc: Timeout after 1 second in write_tcs_reg_sync()")
Reported-by: Maulik Shah <mkshah@codeaurora.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20200528074530.1.Ib86e5b406fe7d16575ae1bb276d650faa144b63c@changeid
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
index 752a5619f715e8e2cb74ea3595634aa2ebb03c42..ae66757825813563f73e56b044438038405c9c7b 100644 (file)
--- a/drivers/soc/qcom/rpmh-rsc.c
+++ b/drivers/soc/qcom/rpmh-rsc.c
@@ -175,13 +175,21 @@ static void write_tcs_reg(const struct rsc_drv *drv, int reg, int tcs_id,
 static void write_tcs_reg_sync(const struct rsc_drv *drv, int reg, int tcs_id,
                               u32 data)
 {
-       u32 new_data;
+       int i;
 
        writel(data, tcs_reg_addr(drv, reg, tcs_id));
-       if (readl_poll_timeout_atomic(tcs_reg_addr(drv, reg, tcs_id), new_data,
-                                     new_data == data, 1, USEC_PER_SEC))
-               pr_err("%s: error writing %#x to %d:%#x\n", drv->name,
-                      data, tcs_id, reg);
+
+       /*
+        * Wait until we read back the same value.  Use a counter rather than
+        * ktime for timeout since this may be called after timekeeping stops.
+        */
+       for (i = 0; i < USEC_PER_SEC; i++) {
+               if (readl(tcs_reg_addr(drv, reg, tcs_id)) == data)
+                       return;
+               udelay(1);
+       }
+       pr_err("%s: error writing %#x to %d:%#x\n", drv->name,
+              data, tcs_id, reg);
 }
 
 /**