Hi,
On 2017/11/16 15:47, Ulf Hansson wrote:
On 14 November 2017 at 23:55, Wolfram Sang
<wsa+renesas@xxxxxxxxxxxxxxxxxxxx> wrote:
Documentation/timers/timers-howto.txt recommends to use usleep_range for
delays 1-20ms. Let's adhere to it. No need for messing with HZ and still
do busy looping these days.
Sorry for chime in this topic but I think for some cases, for instance,
mmc_host_set_uhs_voltage calls mmc_delay and it should guarantee the
delay is accurate, especially for the comment"Keep clock gated for at
least 10 ms, though spec only says 5 ms"
But the usleep_range won't guarantee that, see
https://patchwork.kernel.org/patch/9369963/
It wasn't fixed at the end, so you should carefully modify
this fundamentally.
Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
---
Here is a more detailed test page for this describing my tests:
https://elinux.org/Tests:mmc-delay-refactor
I did mainly test the insert/eject cycle because powering up the cards
seemed to trigger most delays. Transferring data did not cause any calls
to mmc_delay() for me. Please let me know if someone knows a test pattern
which should be included before applying this change.
Works fine for me on Lager (R-Car H2) and Salvator-X (R-Car M3-W). Testing on
other platforms very welcome. This should be independent of the IP core.
drivers/mmc/core/core.h | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h
index 71e6c6d7ceb70d..b2877e2d740fa5 100644
--- a/drivers/mmc/core/core.h
+++ b/drivers/mmc/core/core.h
@@ -62,12 +62,10 @@ void mmc_set_initial_state(struct mmc_host *host);
static inline void mmc_delay(unsigned int ms)
{
- if (ms < 1000 / HZ) {
- cond_resched();
- mdelay(ms);
- } else {
+ if (ms <= 20)
+ usleep_range(ms * 1000, ms * 1250);
This means we get usleep_range(20000, 25000) for the worst case.
Perhaps we want "ms <= 16" instead, thus getting usleep
usleep_range(16000, 20000) for the worst case? No?
+ else
msleep(ms);
- }
}
Kind regards
Uffe
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