| Message ID | 20160904020535.2bb2ab68@vm (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, Sep 04, 2016 at 02:05:35AM +0200, Matthias Seidel wrote: > /* clk_div doesn't support odd number */ > - chip->clk_div = (dws->max_freq / transfer->speed_hz + 1) & 0xfffe; > + chip->clk_div = ((dws->max_freq + transfer->speed_hz) / > + transfer->speed_hz + 1) & 0xfffe; Can we not use DIV_ROUND_UP here if that's what we're trying to do? The above probably needs a comment if not, I'm finding the intent rather confusing looking at the code.
diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c index c85e4b3..2fd517d 100644 --- a/drivers/spi/spi-dw.c +++ b/drivers/spi/spi-dw.c @@ -300,7 +300,8 @@ static int dw_spi_transfer_one(struct spi_master *master, if (transfer->speed_hz != dws->current_freq) { if (transfer->speed_hz != chip->speed_hz) { /* clk_div doesn't support odd number */ - chip->clk_div = (dws->max_freq / transfer->speed_hz + 1) & 0xfffe; + chip->clk_div = ((dws->max_freq + transfer->speed_hz) / + transfer->speed_hz + 1) & 0xfffe; chip->speed_hz = transfer->speed_hz; } dws->current_freq = transfer->speed_hz;
Avoid ending up with a higher frequency than requested Signed-off-by: Matthias Seidel <kernel@mseidel.net> --- Previously failing example: requested transfer freq: 16MHz max_freq = 200MHz calculated clk_div = 12 actual frequency = 200/12 = 16.6666MHz --- drivers/spi/spi-dw.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)