On Wed, 14 Mar 2012 22:04:25 +0100 (CET), Guennadi Liakhovetski
<g.liakhovet...@gmx.de> wrote:
> This patch adds a PM QoS requirement to the spi-bitbang driver, preventing
> the underlying SPI hardware driver to suspend for too long a time, as long
> as there are transfers on the queue.
>
> Signed-off-by: Guennadi Liakhovetski <g.liakhovet...@gmx.de>
Shouldn't this be part of the core spi infrastructure? Particularly since
queuing
is moving into the core.
g.
> ---
>
> RFC, because a patch set has been developed recently, adding a PM QoS
> sysfs attribute to all supporting devices per
> dev_pm_qos_expose_latency_limit(). But I'm not sure, whether and how to
> combine user-space supplied constraint with driver's own idea of which
> code paths should be executed with amended latency requirements. Maybe
> this should be discussed separately, though.
>
> drivers/spi/spi-bitbang.c | 6 ++++++
> include/linux/spi/spi_bitbang.h | 2 ++
> 2 files changed, 8 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/spi/spi-bitbang.c b/drivers/spi/spi-bitbang.c
> index aef59b1..497e725 100644
> --- a/drivers/spi/spi-bitbang.c
> +++ b/drivers/spi/spi-bitbang.c
> @@ -24,6 +24,7 @@
> #include <linux/delay.h>
> #include <linux/errno.h>
> #include <linux/platform_device.h>
> +#include <linux/pm_qos.h>
> #include <linux/slab.h>
>
> #include <linux/spi/spi.h>
> @@ -260,6 +261,8 @@ static void bitbang_work(struct work_struct *work)
> struct spi_bitbang *bitbang =
> container_of(work, struct spi_bitbang, work);
> unsigned long flags;
> + int pmrq = dev_pm_qos_add_request(bitbang->master->dev.parent,
> + &bitbang->pm_qos, 100);
>
> spin_lock_irqsave(&bitbang->lock, flags);
> bitbang->busy = 1;
> @@ -376,6 +379,9 @@ static void bitbang_work(struct work_struct *work)
> }
> bitbang->busy = 0;
> spin_unlock_irqrestore(&bitbang->lock, flags);
> +
> + if (pmrq >= 0)
> + dev_pm_qos_remove_request(&bitbang->pm_qos);
> }
>
> /**
> diff --git a/include/linux/spi/spi_bitbang.h b/include/linux/spi/spi_bitbang.h
> index f987a2b..bed583f1 100644
> --- a/include/linux/spi/spi_bitbang.h
> +++ b/include/linux/spi/spi_bitbang.h
> @@ -1,6 +1,7 @@
> #ifndef __SPI_BITBANG_H
> #define __SPI_BITBANG_H
>
> +#include <linux/pm_qos.h>
> #include <linux/workqueue.h>
>
> struct spi_bitbang {
> @@ -12,6 +13,7 @@ struct spi_bitbang {
> u8 busy;
> u8 use_dma;
> u8 flags; /* extra spi->mode support */
> + struct dev_pm_qos_request pm_qos;
>
> struct spi_master *master;
>
> --
> 1.7.2.5
>
>
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--
Grant Likely, B.Sc, P.Eng.
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