Re: [PATCH v6 1/6] clk: sifive: Add pcie_aux clock in prci driver for PCIe driver

On Tue, May 04, 2021 at 11:23:31AM -0500, Bjorn Helgaas wrote:

On Tue, May 04, 2021 at 03:24:19PM +0300, Leon Romanovsky wrote:

quoted

On Tue, May 04, 2021 at 06:59:35PM +0800, Greentime Hu wrote:

quoted

We add pcie_aux clock in this patch so that pcie driver can use
clk_prepare_enable() and clk_disable_unprepare() to enable and disable
pcie_aux clock.

Signed-off-by: Greentime Hu <greentime.hu@sifive.com>
Acked-by: Stephen Boyd <sboyd@kernel.org>
---
 drivers/clk/sifive/fu740-prci.c               | 11 +++++
 drivers/clk/sifive/fu740-prci.h               |  2 +-
 drivers/clk/sifive/sifive-prci.c              | 41 +++++++++++++++++++
 drivers/clk/sifive/sifive-prci.h              |  9 ++++
 include/dt-bindings/clock/sifive-fu740-prci.h |  1 +
 5 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/sifive/fu740-prci.c b/drivers/clk/sifive/fu740-prci.c
index 764d1097aa51..53f6e00a03b9 100644
--- a/drivers/clk/sifive/fu740-prci.c
+++ b/drivers/clk/sifive/fu740-prci.c

@@ -72,6 +72,12 @@ static const struct clk_ops sifive_fu740_prci_hfpclkplldiv_clk_ops = {
 	.recalc_rate = sifive_prci_hfpclkplldiv_recalc_rate,

<...>

quoted

+/* PCIE AUX clock APIs for enable, disable. */
+int sifive_prci_pcie_aux_clock_is_enabled(struct clk_hw *hw)

It should be bool

It's used via this function pointer:

  struct clk_ops {
    int             (*is_enabled)(struct clk_hw *hw);

so I think "int" is actually appropriate here.

Ahh, sorry, I missed that assignment.

There are some weird/interesting bool vs int usages nearby, though:

  "bool __is_clk_gate_enabled()" goes to some trouble to convert
  int to bool ("return (reg_val & bit_mask) != 0;"), and then
  kona_peri_clk_is_enabled() converts the bool back to int ("return
  is_clk_gate_enabled(bcm_clk->ccu, gate) ? 1 : 0;").

  "int lpc32xx_clk_gate_is_enabled()" actually returns a bool that is
  implicitly converted to int.

  Many *_is_enabled() functions return !!(...) where !! is an
  int-to-bool conversion that is arguably unnecessary and again
  results in an implicit conversion to int.

I don't see any *problems* with any of these; it just seems like a
little more mental effort to think about all the explicit and implicit
conversions going on.

The code is written once but read many times and I can't agree with
your that examples given by you are not the *problems*. They clearly
says "the API is not great and easily can be improved".

Driver authors struggled to write bool-to-int conversion, it is very
optimistic view that they won't struggle to read code too.

Thanks