| Message ID | 20190131094021.3092-4-horms+renesas@verge.net.au (mailing list archive) |
|---|---|
| State | Awaiting Upstream, archived |
| Headers | show |
| Series | clk: renesas: r8a77990: Add Z2 clock | expand |
On Thu, Jan 31, 2019 at 10:40 AM Simon Horman <horms+renesas@verge.net.au> wrote: > Support Z and Z2 clocks with parent frequencies greater than > UINT32_MAX Hz (~4.29GHz). > > The DIV_ROUND_CLOSEST_ULL() macro accepts a 64bit numerator and 32bit > denominator. This leads to truncation of the numerator, which is the Z or > Z2 parent clock frequency in HZ, on platforms where frequency of that clock > is greater than UINT32_MAX Hz. > > To resolve this problem the DIV_ROUND_CLOSEST() macro, which accepts the > prevailing types of the numerator and denominator, is used. In this case > the type of the numerator is unsigned long long (64 bit) and the type of > the denominator is unsigned long (64bit on 64bit platforms and 32bit on > 32bit platforms). This allows parents whose frequency is greater than > UINT32_MAX Hz on 64bit platforms. > > This appears to be sufficient as this driver is only intended for use > on 64bit systems. And in particular, the motivation for this change is > to allow a 4.8GHz clock on the R-Car Gen3 E3 (r8a77990) SoC which is > a 64bit platform. > > Signed-off-by: Simon Horman <horms+renesas@verge.net.au> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be> Gr{oetje,eeting}s, Geert
diff --git a/drivers/clk/renesas/rcar-gen3-cpg.c b/drivers/clk/renesas/rcar-gen3-cpg.c index 6b146c2cf6a3..236a7d9d94bd 100644 --- a/drivers/clk/renesas/rcar-gen3-cpg.c +++ b/drivers/clk/renesas/rcar-gen3-cpg.c @@ -120,8 +120,7 @@ static int cpg_z_clk_set_rate(struct clk_hw *hw, unsigned long rate, unsigned int i; u32 val, kick; - mult = DIV_ROUND_CLOSEST_ULL(rate * 32ULL * zclk->fixed_div, - parent_rate); + mult = DIV_ROUND_CLOSEST(rate * 32ULL * zclk->fixed_div, parent_rate); mult = clamp(mult, 1U, 32U); if (readl(zclk->kick_reg) & CPG_FRQCRB_KICK)
Support Z and Z2 clocks with parent frequencies greater than UINT32_MAX Hz (~4.29GHz). The DIV_ROUND_CLOSEST_ULL() macro accepts a 64bit numerator and 32bit denominator. This leads to truncation of the numerator, which is the Z or Z2 parent clock frequency in HZ, on platforms where frequency of that clock is greater than UINT32_MAX Hz. To resolve this problem the DIV_ROUND_CLOSEST() macro, which accepts the prevailing types of the numerator and denominator, is used. In this case the type of the numerator is unsigned long long (64 bit) and the type of the denominator is unsigned long (64bit on 64bit platforms and 32bit on 32bit platforms). This allows parents whose frequency is greater than UINT32_MAX Hz on 64bit platforms. This appears to be sufficient as this driver is only intended for use on 64bit systems. And in particular, the motivation for this change is to allow a 4.8GHz clock on the R-Car Gen3 E3 (r8a77990) SoC which is a 64bit platform. Signed-off-by: Simon Horman <horms+renesas@verge.net.au> --- v2: New patch --- drivers/clk/renesas/rcar-gen3-cpg.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)