diff options
author | Douglas Anderson <dianders@chromium.org> | 2018-09-06 15:49:06 -0700 |
---|---|---|
committer | Andy Gross <andy.gross@linaro.org> | 2018-09-13 15:54:21 -0500 |
commit | 867d4aa7013fdee8b962cde1711f96c8dd86d926 (patch) | |
tree | 305f799c80c3e3fcbcf485069f16047511f2b892 /drivers/soc/qcom | |
parent | e11bbcedecae85ce60a5d99ea03528c2d6f867e0 (diff) | |
download | linux-867d4aa7013fdee8b962cde1711f96c8dd86d926.tar.bz2 |
soc: qcom: geni: geni_se_clk_freq_match() should always accept multiples
The geni_se_clk_freq_match() has some strange semantics. Specifically
it is defined with two modes:
1. It can find a clock that's an exact multiple of the requested rate
2. It can find a non-exact match but it can't handle multiples then
...but callers should always be able to handle a clock that is a
multiple of the requested clock so mode #2 doesn't really make sense.
Let's change the semantics so that the non-exact match can also accept
multiples and then change the code to handle that.
The only caller of this code is the unlanded SPI driver [1] which
currently passes "exact = True", thus it should be safe to change the
semantics in this way. ...and, in fact, the SPI driver should likely
be modified to pass "exact = False" (with the new semantics) since
that will allow it to work with SPI devices that request a clock rate
that doesn't exactly match a rate we can make.
[1] https://lkml.kernel.org/r/1535107336-2214-1-git-send-email-dkota@codeaurora.org
Fixes: eddac5af0654 ("soc: qcom: Add GENI based QUP Wrapper driver")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>
Diffstat (limited to 'drivers/soc/qcom')
-rw-r--r-- | drivers/soc/qcom/qcom-geni-se.c | 37 |
1 files changed, 22 insertions, 15 deletions
diff --git a/drivers/soc/qcom/qcom-geni-se.c b/drivers/soc/qcom/qcom-geni-se.c index 1b19b8428c4a..ee89ffb6dde8 100644 --- a/drivers/soc/qcom/qcom-geni-se.c +++ b/drivers/soc/qcom/qcom-geni-se.c @@ -544,16 +544,17 @@ EXPORT_SYMBOL(geni_se_clk_tbl_get); * @se: Pointer to the concerned serial engine. * @req_freq: Requested clock frequency. * @index: Index of the resultant frequency in the table. - * @res_freq: Resultant frequency which matches or is closer to the - * requested frequency. + * @res_freq: Resultant frequency of the source clock. * @exact: Flag to indicate exact multiple requirement of the requested * frequency. * - * This function is called by the protocol drivers to determine the matching - * or exact multiple of the requested frequency, as provided by the serial - * engine clock in order to meet the performance requirements. If there is - * no matching or exact multiple of the requested frequency found, then it - * selects the closest floor frequency, if exact flag is not set. + * This function is called by the protocol drivers to determine the best match + * of the requested frequency as provided by the serial engine clock in order + * to meet the performance requirements. + * + * If we return success: + * - if @exact is true then @res_freq / <an_integer> == @req_freq + * - if @exact is false then @res_freq / <an_integer> <= @req_freq * * Return: 0 on success, standard Linux error codes on failure. */ @@ -564,6 +565,9 @@ int geni_se_clk_freq_match(struct geni_se *se, unsigned long req_freq, unsigned long *tbl; int num_clk_levels; int i; + unsigned long best_delta; + unsigned long new_delta; + unsigned int divider; num_clk_levels = geni_se_clk_tbl_get(se, &tbl); if (num_clk_levels < 0) @@ -572,18 +576,21 @@ int geni_se_clk_freq_match(struct geni_se *se, unsigned long req_freq, if (num_clk_levels == 0) return -EINVAL; - *res_freq = 0; + best_delta = ULONG_MAX; for (i = 0; i < num_clk_levels; i++) { - if (!(tbl[i] % req_freq)) { + divider = DIV_ROUND_UP(tbl[i], req_freq); + new_delta = req_freq - tbl[i] / divider; + if (new_delta < best_delta) { + /* We have a new best! */ *index = i; *res_freq = tbl[i]; - return 0; - } - if (!(*res_freq) || ((tbl[i] > *res_freq) && - (tbl[i] < req_freq))) { - *index = i; - *res_freq = tbl[i]; + /* If the new best is exact then we're done */ + if (new_delta == 0) + return 0; + + /* Record how close we got */ + best_delta = new_delta; } } |