Some MMC hosts implement a fine-grained runtime PM, whereby they
runtime-suspend and -resume the host interface on each transfer. This can
negatively affect performance, if the user was trying to transfer data
blocks back-to-back. This patch adds a PM QoS constraint to avoid such a
throughput reduction. This constraint prevents runtime-suspending the
device, if the expected wakeup latency is larger than 100us.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
---
This patch has been tested on SuperH and ARM sh-mobile hosts with
sh_mobile_sdhi and sh_mmcif drivers. Would be good to also have it tested
on other platforms, enabling PM QoS, e.g., those, using the simple QoS
PM domain governor.
drivers/mmc/core/core.c | 16 +++++++++++++++-
include/linux/mmc/host.h | 2 ++
2 files changed, 17 insertions(+), 1 deletions(-)
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index b27b940..40f666f 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -22,6 +22,7 @@
#include <linux/scatterlist.h>
#include <linux/log2.h>
#include <linux/regulator/consumer.h>
+#include <linux/pm_domain.h>
#include <linux/pm_runtime.h>
#include <linux/suspend.h>
@@ -589,8 +590,16 @@ int __mmc_claim_host(struct mmc_host *host, atomic_t *abort)
wake_up(&host->wq);
spin_unlock_irqrestore(&host->lock, flags);
remove_wait_queue(&host->wq, &wait);
- if (!stop)
+ if (!stop) {
+ if (host->claim_cnt == 1) {
+ int ret = dev_pm_qos_add_request(host->parent,
+ &host->pm_qos, 100);
+ if (ret < 0)
+ dev_err(host->parent,
+ "PM QoS request failed: %d\n", ret);
+ }
mmc_host_enable(host);
+ }
return stop;
}
@@ -615,6 +624,10 @@ int mmc_try_claim_host(struct mmc_host *host)
claimed_host = 1;
}
spin_unlock_irqrestore(&host->lock, flags);
+
+ if (claimed_host && host->claim_cnt == 1)
+ dev_pm_qos_add_request(host->parent, &host->pm_qos, 100);
+
return claimed_host;
}
EXPORT_SYMBOL(mmc_try_claim_host);
@@ -639,6 +652,7 @@ void mmc_do_release_host(struct mmc_host *host)
host->claimer = NULL;
spin_unlock_irqrestore(&host->lock, flags);
wake_up(&host->wq);
+ dev_pm_qos_remove_request(&host->pm_qos);
}
}
EXPORT_SYMBOL(mmc_do_release_host);
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 1d09562..3e9d2f3 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -11,6 +11,7 @@
#define LINUX_MMC_HOST_H
#include <linux/leds.h>
+#include <linux/pm_qos.h>
#include <linux/sched.h>
#include <linux/mmc/core.h>
@@ -175,6 +176,7 @@ struct mmc_host {
u32 ocr_avail_sd; /* SD-specific OCR */
u32 ocr_avail_mmc; /* MMC-specific OCR */
struct notifier_block pm_notify;
+ struct dev_pm_qos_request pm_qos;
#define MMC_VDD_165_195 0x00000080 /* VDD voltage 1.65 - 1.95 */
#define MMC_VDD_20_21 0x00000100 /* VDD voltage 2.0 ~ 2.1 */
--
1.7.2.5
--
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