opp: Use clk_get_optional() to avoid leaving opp_table->clk as an error pointer

_update_opp_table_clk() uses clk_get(dev, NULL) to acquire the
device's clock. On platforms where the perf domain device has no
Linux clock and is instead managed entirely by firmware via
devm_pm_opp_of_add_table() (through
of_genpd_add_provider_simple()/onecell()), clk_get() returns
-ENOENT. That case is treated as valid (the OPP table can still
have entries sourced from firmware), but opp_table->clk is left
holding ERR_PTR(-ENOENT) rather than being reset to NULL:

	opp_table->clk = clk_get(dev, NULL);
	ret = PTR_ERR_OR_ZERO(opp_table->clk);
	...
	if (ret == -ENOENT) {
		opp_table->clk_count = 1;
		return opp_table;   /* opp_table->clk is still ERR_PTR(-ENOENT) */
	}

Consumers that only check IS_ERR(opp_table->clk) treat this as a
valid clk and pass it straight into the clk consumer API. In
particular, dev_pm_opp_set_rate() calls
clk_round_rate(opp_table->clk, target_freq), and clk_round_rate()
only guards against a NULL clk, so it dereferences the error pointer
to read clk->exclusive_count and crashes:

  Unable to handle kernel NULL pointer dereference at virtual
  address 000000000000002e
  ...
  pc : clk_round_rate+0x3c/0x188
  ...
  Call trace:
   clk_round_rate+0x3c/0x188 (P)
   dev_pm_opp_set_rate+0x114/0x33c

Rather than teaching every clk consumer API to special-case
ERR_PTR(-ENOENT), fix it at the source: use clk_get_optional()
instead of clk_get() in _update_opp_table_clk(), which already
translates -ENOENT into a NULL clk. This documents that the clock is
genuinely optional for such devices, and keeps opp_table->clk holding
either a valid clk or NULL, never a lingering -ENOENT error pointer.
_opp_config_clk_single() is only wired up via opp_table->config_clks
when a clk was actually found, and every other opp_table->clk
consumer already tolerates NULL through the standard clk API (which
treats a NULL clk as a no-op), so no other call site needs to change.

Suggested-by: Sebastian Reichel <sre@kernel.org>
Reviewed-by: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Praveen Talari <praveen.talari@oss.qualcomm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

0 files changed, 0 insertions, 0 deletions