Re: [PATCH] [v2] mmc: esdhc-imx: convert to modern PM_OPS

[Adrian Hunter <adrian.hunter@intel.com>]

On 11/04/25 11:59, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> Two newly added functions are unused in configurations without
> power management support:
> 
> drivers/mmc/host/sdhci-esdhc-imx.c:1586:13: error: unused function 'sdhc_esdhc_tuning_save' [-Werror,-Wunused-function]
>  1586 | static void sdhc_esdhc_tuning_save(struct sdhci_host *host)
>       |             ^~~~~~~~~~~~~~~~~~~~~~
> drivers/mmc/host/sdhci-esdhc-imx.c:1608:13: error: unused function 'sdhc_esdhc_tuning_restore' [-Werror,-Wunused-function]
>  1608 | static void sdhc_esdhc_tuning_restore(struct sdhci_host *host)
>       |             ^~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Remove the #ifdef checks and instead use the better macros that
> silently drop the unused functions when PM is disabled. This also
> requires using pm_ptr() to eliminate both the runtime and pm_sleep
> operations.

This explanation is still a bit mysterious.  SYSTEM_SLEEP_PM_OPS()
and pm_ptr() make use of PTR_IF() which uses a conditional expression
so that the pointers have a reference during compile time but not at
link time.  That way unused functions still get compiled without
triggering -Wunused-function, but get dropped by the linker's
dead code elimination.

It is perhaps worth noting that dead code elimination is not
default unless -O1 or above optimization level is used.  The
kernel currently uses -O2 or -Os both of which do dead code
elimination.

> 
> Fixes: 3d1eea493894 ("mmc: sdhci-esdhc-imx: Save tuning value when card stays powered in suspend")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Nevertheless, together with the chunk from:

https://lore.kernel.org/all/3d544dbc-863d-4ac5-9839-aef3a36881d1@app.fastmail.com/

i.e.

diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index cd0e35a80542..4ee2695b0202 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -874,12 +874,10 @@ irqreturn_t sdhci_thread_irq(int irq, void *dev_id);
 void sdhci_adma_write_desc(struct sdhci_host *host, void **desc,
                           dma_addr_t addr, int len, unsigned int cmd);
 
-#ifdef CONFIG_PM
 int sdhci_suspend_host(struct sdhci_host *host);
 int sdhci_resume_host(struct sdhci_host *host);
 int sdhci_runtime_suspend_host(struct sdhci_host *host);
 int sdhci_runtime_resume_host(struct sdhci_host *host, int soft_reset);
-#endif
 
 void sdhci_cqe_enable(struct mmc_host *mmc);
 void sdhci_cqe_disable(struct mmc_host *mmc, bool recovery);


Acked-by: Adrian Hunter <adrian.hunter@intel.com>


> ---
> v2: add pm_ptr()
> ---
>  drivers/mmc/host/sdhci-esdhc-imx.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
> index 7e8addaed697..3c2e50d0260d 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -1942,7 +1942,6 @@ static void sdhci_esdhc_imx_remove(struct platform_device *pdev)
>  	sdhci_pltfm_free(pdev);
>  }
>  
> -#ifdef CONFIG_PM_SLEEP
>  static int sdhci_esdhc_suspend(struct device *dev)
>  {
>  	struct sdhci_host *host = dev_get_drvdata(dev);
> @@ -2021,9 +2020,7 @@ static int sdhci_esdhc_resume(struct device *dev)
>  
>  	return ret;
>  }
> -#endif
>  
> -#ifdef CONFIG_PM
>  static int sdhci_esdhc_runtime_suspend(struct device *dev)
>  {
>  	struct sdhci_host *host = dev_get_drvdata(dev);
> @@ -2103,11 +2100,10 @@ static int sdhci_esdhc_runtime_resume(struct device *dev)
>  		cpu_latency_qos_remove_request(&imx_data->pm_qos_req);
>  	return err;
>  }
> -#endif
>  
>  static const struct dev_pm_ops sdhci_esdhc_pmops = {
> -	SET_SYSTEM_SLEEP_PM_OPS(sdhci_esdhc_suspend, sdhci_esdhc_resume)
> -	SET_RUNTIME_PM_OPS(sdhci_esdhc_runtime_suspend,
> +	SYSTEM_SLEEP_PM_OPS(sdhci_esdhc_suspend, sdhci_esdhc_resume)
> +	RUNTIME_PM_OPS(sdhci_esdhc_runtime_suspend,
>  				sdhci_esdhc_runtime_resume, NULL)
>  };
>  
> @@ -2116,7 +2112,7 @@ static struct platform_driver sdhci_esdhc_imx_driver = {
>  		.name	= "sdhci-esdhc-imx",
>  		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
>  		.of_match_table = imx_esdhc_dt_ids,
> -		.pm	= &sdhci_esdhc_pmops,
> +		.pm	= pm_ptr(&sdhci_esdhc_pmops),
>  	},
>  	.probe		= sdhci_esdhc_imx_probe,
>  	.remove		= sdhci_esdhc_imx_remove,