Re: [PATCH] clk: qcom: clk-alpha-pll: Replace divide operator with comparison

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Hi Satya,

On 30/08/2024 06:33, Satya Priya Kakitapalli wrote:
Hi Jon,


On 8/28/2024 7:17 PM, Jon Hunter wrote:
Hi Satya, Vladimir,

On 13/08/2024 21:01, Vladimir Zapolskiy wrote:
On 8/13/24 12:40, Satya Priya Kakitapalli wrote:
In zonda_pll_adjust_l_val() replace the divide operator with comparison
operator since comparisons are faster than divisions.

Fixes: f4973130d255 ("clk: qcom: clk-alpha-pll: Update set_rate for Zonda PLL")

Apparently the change is not a fix, therefore I believe the Fixes tag
shall be removed.


From the commit message it is not clear that this is a fix, but I
believe that it is. With the current -next I am seeing the following
build error (with GCC 7.3.1) on ARM ...

drivers/clk/qcom/clk-alpha-pll.o: In function `clk_zonda_pll_set_rate':
clk-alpha-pll.c:(.text+0x45dc): undefined reference to `__aeabi_uldivmod'

Reported-by: kernel test robot <lkp@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Closes: https://lore.kernel.org/r/202408110724.8pqbpDiD-lkp@xxxxxxxxx/

There is also the above smatch warning that was reported.

Signed-off-by: Satya Priya Kakitapalli <quic_skakitap@xxxxxxxxxxx>
---
  drivers/clk/qcom/clk-alpha-pll.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/qcom/clk-alpha-pll.c b/drivers/clk/qcom/clk-alpha-pll.c
index 2f620ccb41cb..fd8a82bb3690 100644
--- a/drivers/clk/qcom/clk-alpha-pll.c
+++ b/drivers/clk/qcom/clk-alpha-pll.c
@@ -2126,7 +2126,7 @@ static void zonda_pll_adjust_l_val(unsigned long rate, unsigned long prate, u32
      remainder = do_div(quotient, prate);
      *l = quotient;

Since it's not a fix, but a simplification, you may wish to remove
an unnecessary 'quotient' local variable:

remainder = do_div(rate, prate);

-    if ((remainder * 2) / prate)
+    if ((remainder * 2) >= prate)
          *l = *l + 1;

*l = rate + (u32)(remainder * 2 >= prate);


The above change does fix this build error for me.

Satya, did you intend this to be a fix? Can we get this into -next?


Yes, I have posted a v2 for this last week, but there are few open comments on that, I'll address them and post V3 including the build error you reported in commit-text.


[v2] https://lore.kernel.org/linux-clk/20240814102005.33493-1-quic_skakitap@xxxxxxxxxxx/


Have you push a V3 yet?

Thanks
Jon

--
nvpublic




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