> -----Original Message----- > From: Arnd Bergmann [mailto:arnd@xxxxxxxx] > Sent: Tuesday, May 31, 2016 11:17 AM > To: Baranowska, BeataX <beatax.baranowska@xxxxxxxxx> > Cc: Hunter, Adrian <adrian.hunter@xxxxxxxxx>; Ulf Hansson > <ulf.hansson@xxxxxxxxxx>; linux-mmc@xxxxxxxxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; Dong, Chuanxiao <chuanxiao.dong@xxxxxxxxx>; > Jarosz, SebastianX <sebastianx.jarosz@xxxxxxxxx> > Subject: Re: [PATCH] mmc: sdhci: use udelay instead of mdelay > > On Tuesday, May 31, 2016 8:53:18 AM CEST Baranowska, BeataX wrote: > > > > > > On Monday, May 30, 2016 7:55:55 AM CEST Baranowska, BeataX wrote: > > > > From: Chuanxiao Dong <chuanxiao.dong@xxxxxxxxx> > > > > > > > > This patch will use udelay instead of mdelay when waiting for > > > > SDHCI hardware to be stable. udelay can help to reduce the waiting > > > > time when is in critical region which is protected by spinlock. > > > > > > > > With this patch, __sdhci_set_ios only take a few microseconds to > > > > be done. > > > > > > > > Signed-off-by: Chuanxiao Dong <chuanxiao.dong@xxxxxxxxx> > > > > --- > > > > drivers/mmc/host/sdhci.c | 18 +++++++++--------- > > > > 1 file changed, 9 insertions(+), 9 deletions(-) > > > > > > > > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c > > > > index > > > > e010ea4eb6f5..56d2c7567d97 100644 > > > > --- a/drivers/mmc/host/sdhci.c > > > > +++ b/drivers/mmc/host/sdhci.c > > > > @@ -173,8 +173,8 @@ void sdhci_reset(struct sdhci_host *host, u8 > mask) > > > > sdhci_runtime_pm_bus_off(host); > > > > } > > > > > > > > - /* Wait max 100 ms */ > > > > - timeout = 100; > > > > + /* Wait max 10000 ms */ > > > > + timeout = 10000; > > > > > > > > /* hw clears the bit when it's done */ > > > > while (sdhci_readb(host, SDHCI_SOFTWARE_RESET) & mask) { > > > > @@ > > > > -185,7 +185,7 @@ void sdhci_reset(struct sdhci_host *host, u8 mask) > > > > return; > > > > } > > > > timeout--; > > > > - mdelay(1); > > > > + udelay(10); > > > > } > > > > } > > > > EXPORT_SYMBOL_GPL(sdhci_reset); > > > > > > This can significantly increase the timeout length. I think you > > > should instead use time_before() to see how many jiffies have passed > since the start. > > > > > > However, the real question is why the reset function gets called > > > under a spinlock in the first place. Can you try to rearrange the > > > code so it doesn't need the lock at all and you can just use msleep() > instead? > > > > > > Arnd > > > > Thank you for your quick reply. > > Could you please clarify what do you mean is called under a spinlock? > > Any is not used here? > > You write that the function is called in a critical region protected by the > spinlock, so I was wondering if that is actually necessary. > > Usually a device reset should be done in normal process context without any > spinlocks so you can call normal sleeping functions. > > Arnd Ok I understand now. Thank you. Beata Baranowska -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
