diff mbox series

media: mxl5xx: Move xpt structures off stack

Message ID 20240111-dvb-mxl5xx-move-structs-off-stack-v1-1-ca4230e67c11@kernel.org (mailing list archive)
State Accepted
Headers
Series media: mxl5xx: Move xpt structures off stack |

Commit Message

Nathan Chancellor Jan. 12, 2024, 12:40 a.m. UTC 
  When building for LoongArch with clang 18.0.0, the stack usage of
probe() is larger than the allowed 2048 bytes:

  drivers/media/dvb-frontends/mxl5xx.c:1698:12: warning: stack frame size (2368) exceeds limit (2048) in 'probe' [-Wframe-larger-than]
   1698 | static int probe(struct mxl *state, struct mxl5xx_cfg *cfg)
        |            ^
  1 warning generated.

This is the result of the linked LLVM commit, which changes how the
arrays of structures in config_ts() get handled with
CONFIG_INIT_STACK_ZERO and CONFIG_INIT_STACK_PATTERN, which causes the
above warning in combination with inlining, as config_ts() gets inlined
into probe().

This warning can be easily fixed by moving the array of structures off
of the stackvia 'static const', which is a better location for these
variables anyways because they are static data that is only ever read
from, never modified, so allocating the stack space is wasteful.

This drops the stack usage from 2368 bytes to 256 bytes with the same
compiler and configuration.

Cc: stable@vger.kernel.org
Closes: https://github.com/ClangBuiltLinux/linux/issues/1977
Link: https://github.com/llvm/llvm-project/commit/afe8b93ffdfef5d8879e1894b9d7dda40dee2b8d
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 drivers/media/dvb-frontends/mxl5xx.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)


---
base-commit: 02d4e62ae2452c83e4a3e279b8e4cb4dcbad4b31
change-id: 20240111-dvb-mxl5xx-move-structs-off-stack-e12172b1ef02

Best regards,

Comments

Miguel Ojeda Feb. 10, 2024, 4:26 p.m. UTC | #1 
> On Thu, 11 Jan 2024 17:40:36 -0700 Nathan Chancellor <nathan@kernel.org> wrote:
>
> Closes: https://github.com/ClangBuiltLinux/linux/issues/1977

The next one: 1978 :)

> of the stackvia 'static const', which is a better location for these

Nit: space.

Built-tested for loongarch64:

Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Miguel Ojeda <ojeda@kernel.org>

With this applied, I have a `WERROR`-clean `defconfig` build with a Rust-enabled
kernel using LLVM 18 (using LLVM-provided apt pre-releases).

Thanks Nathan!

Cheers,
Miguel
Nathan Chancellor Feb. 12, 2024, 11:27 p.m. UTC | #2 
On Sat, Feb 10, 2024 at 05:26:04PM +0100, Miguel Ojeda wrote:
> > On Thu, 11 Jan 2024 17:40:36 -0700 Nathan Chancellor <nathan@kernel.org> wrote:
> >
> > Closes: https://github.com/ClangBuiltLinux/linux/issues/1977
> 
> The next one: 1978 :)

This is probably the third link I have messed up in the past couple of
weeks :/ Mauro, do you want a v2 for these two minor issues or can you
fix them up during application?

> > of the stackvia 'static const', which is a better location for these
> 
> Nit: space.
> 
> Built-tested for loongarch64:
> 
> Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
> Tested-by: Miguel Ojeda <ojeda@kernel.org>
> 
> With this applied, I have a `WERROR`-clean `defconfig` build with a Rust-enabled
> kernel using LLVM 18 (using LLVM-provided apt pre-releases).

Thanks for taking a look, this is great to hear!

Cheers,
Nathan
Miguel Ojeda Feb. 13, 2024, 8:37 p.m. UTC | #3 
On Tue, Feb 13, 2024 at 12:28 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> Thanks for taking a look, this is great to hear!

My pleasure!

I am happy to report that it also worked with the new toolchain you
just uploaded (i.e. the one that included `libclang.so` :)

Cheers,
Miguel
diff mbox series

Patch

diff --git a/drivers/media/dvb-frontends/mxl5xx.c b/drivers/media/dvb-frontends/mxl5xx.c
index 4ebbcf05cc09..91e9c378397c 100644
--- a/drivers/media/dvb-frontends/mxl5xx.c
+++ b/drivers/media/dvb-frontends/mxl5xx.c
@@ -1381,57 +1381,57 @@  static int config_ts(struct mxl *state, enum MXL_HYDRA_DEMOD_ID_E demod_id,
 	u32 nco_count_min = 0;
 	u32 clk_type = 0;
 
-	struct MXL_REG_FIELD_T xpt_sync_polarity[MXL_HYDRA_DEMOD_MAX] = {
+	static const struct MXL_REG_FIELD_T xpt_sync_polarity[MXL_HYDRA_DEMOD_MAX] = {
 		{0x90700010, 8, 1}, {0x90700010, 9, 1},
 		{0x90700010, 10, 1}, {0x90700010, 11, 1},
 		{0x90700010, 12, 1}, {0x90700010, 13, 1},
 		{0x90700010, 14, 1}, {0x90700010, 15, 1} };
-	struct MXL_REG_FIELD_T xpt_clock_polarity[MXL_HYDRA_DEMOD_MAX] = {
+	static const struct MXL_REG_FIELD_T xpt_clock_polarity[MXL_HYDRA_DEMOD_MAX] = {
 		{0x90700010, 16, 1}, {0x90700010, 17, 1},
 		{0x90700010, 18, 1}, {0x90700010, 19, 1},
 		{0x90700010, 20, 1}, {0x90700010, 21, 1},
 		{0x90700010, 22, 1}, {0x90700010, 23, 1} };
-	struct MXL_REG_FIELD_T xpt_valid_polarity[MXL_HYDRA_DEMOD_MAX] = {
+	static const struct MXL_REG_FIELD_T xpt_valid_polarity[MXL_HYDRA_DEMOD_MAX] = {
 		{0x90700014, 0, 1}, {0x90700014, 1, 1},
 		{0x90700014, 2, 1}, {0x90700014, 3, 1},
 		{0x90700014, 4, 1}, {0x90700014, 5, 1},
 		{0x90700014, 6, 1}, {0x90700014, 7, 1} };
-	struct MXL_REG_FIELD_T xpt_ts_clock_phase[MXL_HYDRA_DEMOD_MAX] = {
+	static const struct MXL_REG_FIELD_T xpt_ts_clock_phase[MXL_HYDRA_DEMOD_MAX] = {
 		{0x90700018, 0, 3}, {0x90700018, 4, 3},
 		{0x90700018, 8, 3}, {0x90700018, 12, 3},
 		{0x90700018, 16, 3}, {0x90700018, 20, 3},
 		{0x90700018, 24, 3}, {0x90700018, 28, 3} };
-	struct MXL_REG_FIELD_T xpt_lsb_first[MXL_HYDRA_DEMOD_MAX] = {
+	static const struct MXL_REG_FIELD_T xpt_lsb_first[MXL_HYDRA_DEMOD_MAX] = {
 		{0x9070000C, 16, 1}, {0x9070000C, 17, 1},
 		{0x9070000C, 18, 1}, {0x9070000C, 19, 1},
 		{0x9070000C, 20, 1}, {0x9070000C, 21, 1},
 		{0x9070000C, 22, 1}, {0x9070000C, 23, 1} };
-	struct MXL_REG_FIELD_T xpt_sync_byte[MXL_HYDRA_DEMOD_MAX] = {
+	static const struct MXL_REG_FIELD_T xpt_sync_byte[MXL_HYDRA_DEMOD_MAX] = {
 		{0x90700010, 0, 1}, {0x90700010, 1, 1},
 		{0x90700010, 2, 1}, {0x90700010, 3, 1},
 		{0x90700010, 4, 1}, {0x90700010, 5, 1},
 		{0x90700010, 6, 1}, {0x90700010, 7, 1} };
-	struct MXL_REG_FIELD_T xpt_enable_output[MXL_HYDRA_DEMOD_MAX] = {
+	static const struct MXL_REG_FIELD_T xpt_enable_output[MXL_HYDRA_DEMOD_MAX] = {
 		{0x9070000C, 0, 1}, {0x9070000C, 1, 1},
 		{0x9070000C, 2, 1}, {0x9070000C, 3, 1},
 		{0x9070000C, 4, 1}, {0x9070000C, 5, 1},
 		{0x9070000C, 6, 1}, {0x9070000C, 7, 1} };
-	struct MXL_REG_FIELD_T xpt_err_replace_sync[MXL_HYDRA_DEMOD_MAX] = {
+	static const struct MXL_REG_FIELD_T xpt_err_replace_sync[MXL_HYDRA_DEMOD_MAX] = {
 		{0x9070000C, 24, 1}, {0x9070000C, 25, 1},
 		{0x9070000C, 26, 1}, {0x9070000C, 27, 1},
 		{0x9070000C, 28, 1}, {0x9070000C, 29, 1},
 		{0x9070000C, 30, 1}, {0x9070000C, 31, 1} };
-	struct MXL_REG_FIELD_T xpt_err_replace_valid[MXL_HYDRA_DEMOD_MAX] = {
+	static const struct MXL_REG_FIELD_T xpt_err_replace_valid[MXL_HYDRA_DEMOD_MAX] = {
 		{0x90700014, 8, 1}, {0x90700014, 9, 1},
 		{0x90700014, 10, 1}, {0x90700014, 11, 1},
 		{0x90700014, 12, 1}, {0x90700014, 13, 1},
 		{0x90700014, 14, 1}, {0x90700014, 15, 1} };
-	struct MXL_REG_FIELD_T xpt_continuous_clock[MXL_HYDRA_DEMOD_MAX] = {
+	static const struct MXL_REG_FIELD_T xpt_continuous_clock[MXL_HYDRA_DEMOD_MAX] = {
 		{0x907001D4, 0, 1}, {0x907001D4, 1, 1},
 		{0x907001D4, 2, 1}, {0x907001D4, 3, 1},
 		{0x907001D4, 4, 1}, {0x907001D4, 5, 1},
 		{0x907001D4, 6, 1}, {0x907001D4, 7, 1} };
-	struct MXL_REG_FIELD_T xpt_nco_clock_rate[MXL_HYDRA_DEMOD_MAX] = {
+	static const struct MXL_REG_FIELD_T xpt_nco_clock_rate[MXL_HYDRA_DEMOD_MAX] = {
 		{0x90700044, 16, 80}, {0x90700044, 16, 81},
 		{0x90700044, 16, 82}, {0x90700044, 16, 83},
 		{0x90700044, 16, 84}, {0x90700044, 16, 85},