| Message ID | 17296D9F8FF2234F831FC3DF505A87A911B2268E@shsmsx102.ccr.corp.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
> -----Original Message----- > From: Dong, Chuanxiao > Sent: Monday, August 18, 2014 2:19 PM > To: Gao, Yunpeng; linux-mmc@vger.kernel.org > Subject: RE: [PATCH] mmc: core: optimize mmc device power up ramp up time > > > -----Original Message----- > > From: Gao, Yunpeng > > Sent: Monday, August 18, 2014 2:17 PM > > To: linux-mmc@vger.kernel.org > > Cc: Gao, Yunpeng; Dong, Chuanxiao > > Subject: [PATCH] mmc: core: optimize mmc device power up ramp up time > > > > In current kernel mmc driver, it uses two 'msleep(10)' > > for eMMC/SD card power up ramp up time delay. > > > > According to Spec, the ramp up time should be max of 74 eMMC/SD bus > > clock or 1ms. > > Take the worst eMMC/SD card I can image as the example - assume it has > > to work on 32KHz or 16KHz during the card initialzation, then 74 clock > > should be 2.312ms or 4.625ms. > > So, 5ms delay should be enough. > > > > Also, msleep(10) will invlove sechdule and may consume more time than > > what we expected. > > Measured on Merrifield platform showed it consumed almost > > 2*20 = 40ms. This is much more than what we expected. > > > > Submit this patch to reduce the time of mmc boot up and the time of > > mmc D3 resume. > > > > Signed-off-by: Yunpeng Gao <yunpeng.gao@intel.com> > > Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com> > > --- > > drivers/mmc/core/core.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index > > 7dc0c85..7bcb797 100644 > > --- a/drivers/mmc/core/core.c > > +++ b/drivers/mmc/core/core.c > > @@ -1556,7 +1556,7 @@ void mmc_power_up(struct mmc_host *host, u32 > > ocr) > > * This delay should be sufficient to allow the power supply > > * to reach the minimum voltage. > > */ > > - mmc_delay(10); > > + usleep_range(10000, 12000); > > Instead of directly change the mmc_delay to usleep_range, I prefer to do it in > changing the drivers/mmc/core/core.h: > diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h index > 443a584..b7584d8 100644 > --- a/drivers/mmc/core/core.h > +++ b/drivers/mmc/core/core.h > @@ -55,9 +55,10 @@ static inline void mmc_delay(unsigned int ms) > if (ms < 1000 / HZ) { > cond_resched(); > mdelay(ms); > - } else { > + } else if (ms < 20) > + usleep_range(ms * 1000, (ms + 1) * 1000); > + else > msleep(ms); > - } > } > > Thanks > Chuanxiao Thanks Chuanxiao for the comments. I think it's better to redefine mmc_delay() instead of directly changing the mmc_delay() multiple times. In Documentation/timers/timers-howto.txt, it mentioned that 'not msleep for (1ms - 20ms)'. So, I think it's reasonable, in Chuanxiao's patch, to use usleep_range() for delay less than 20ms. > > > > host->ios.clock = host->f_init; > > > > @@ -1567,7 +1567,7 @@ void mmc_power_up(struct mmc_host *host, u32 > > ocr) > > * This delay must be at least 74 clock sizes, or 1 ms, or the > > * time required to reach a stable voltage. > > */ > > - mmc_delay(10); > > + usleep_range(5000, 6000); > > > > mmc_host_clk_release(host); > > } > > -- > > 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h index 443a584..b7584d8 100644 --- a/drivers/mmc/core/core.h +++ b/drivers/mmc/core/core.h @@ -55,9 +55,10 @@ static inline void mmc_delay(unsigned int ms) if (ms < 1000 / HZ) { cond_resched(); mdelay(ms); - } else { + } else if (ms < 20) + usleep_range(ms * 1000, (ms + 1) * 1000); + else msleep(ms); - } } Thanks