Re: [PATCH 2/3] spi: s3c64xx: fix runtime PM handling

[Krzysztof Kozlowski <k.kozlowski@samsung.com>]

On 19.08.2015 06:06, Heiner Kallweit wrote:
> The patch fixes / extends the runtime PM handling.
> - Currently the driver instructs the SPI core to use auto-suspend
>   but doesn't configure it. Add the necessary calls and let it
>   autosuspend after probe.

After quick look at the driver I think it does not use autosuspend
fully. It just sets master->auto_runtime_pm (so the core code will use
autosuspend) but its own calls to pm_runtime_put() are regular ones.
Shouldn't this be enhanced as well?

> - In case the driver registration fails runtime PM needs to be
>   properly disabled.
> 
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> ---
>  drivers/spi/spi-s3c64xx.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
> index c4d3b06..15a6de1 100644
> --- a/drivers/spi/spi-s3c64xx.c
> +++ b/drivers/spi/spi-s3c64xx.c
> @@ -32,6 +32,7 @@
>  #define MAX_SPI_PORTS		6
>  #define S3C64XX_SPI_QUIRK_POLL		(1 << 0)
>  #define S3C64XX_SPI_QUIRK_CS_AUTO	(1 << 1)
> +#define AUTOSUSPEND_TIMEOUT     2000
>  
>  /* Registers and bit-fields */
>  
> @@ -1180,13 +1181,15 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
>  	       S3C64XX_SPI_INT_TX_OVERRUN_EN | S3C64XX_SPI_INT_TX_UNDERRUN_EN,
>  	       sdd->regs + S3C64XX_SPI_INT_EN);
>  
> +	pm_runtime_set_autosuspend_delay(dev, AUTOSUSPEND_TIMEOUT);
> +	pm_runtime_use_autosuspend(dev);
>  	pm_runtime_set_active(dev);
>  	pm_runtime_enable(dev);
>  
>  	ret = devm_spi_register_master(dev, master);
>  	if (ret != 0) {
>  		dev_err(dev, "cannot register SPI master: %d\n", ret);
> -		goto err3;
> +		goto err4;
>  	}
>  
>  	dev_dbg(dev, "Samsung SoC SPI Driver loaded for Bus SPI-%d with %d Slaves attached\n",
> @@ -1195,8 +1198,14 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
>  					mem_res, (FIFO_LVL_MASK(sdd) >> 1) + 1,
>  					sdd->rx_dma.dmach, sdd->tx_dma.dmach);
>  
> +	pm_runtime_mark_last_busy(dev);
> +	pm_runtime_autosuspend(dev);

There is a high chance that device will be suspended already at this
point because pm_runtime_put() in setup. In most cases (when SPI is
started) this won't do anything so we are back at first of my questions
- shouldn't you update pm_runtime_put() calls?

Additionally (which is not related to your patch) shouldn't we
pm_runtime_get() at some point in probe() to be sure that it won't be
suspended to early?

> +
>  	return 0;
>  
> +err4:
> +	pm_runtime_disable(dev);
> +	pm_runtime_set_suspended(dev);

Please separate fixes from enhancements into different patches.

Best regards,
Krzysztof

>  err3:
>  	clk_disable_unprepare(sdd->src_clk);
>  err2:
>