From: Lucas Stach <l.stach@pengutronix.de>
To: barebox@lists.infradead.org
Subject: [PATCH] mci: imx-esdhc: send required clock pulses to card on init
Date: Wed, 25 Jul 2018 11:57:28 +0200 [thread overview]
Message-ID: <20180725095728.16369-1-l.stach@pengutronix.de> (raw)
MMC cards need at least 74 clock pulses before any bus communication
can occur. The i.MX SDHC controller auto-gates the clock when inactive,
so if the SD enumeration is skipped for slots where we know that only a
MMC card can be present (which is possible since
b5289b742a89 "mmc: allow skipping SD card initialization") those
inititialization clock pulses won't be sent out, resulting in command
timeouts when trying to enumerate the card.
Luckily the eSDHC controller has a hardware feature to send out 80
clock pulses. This has been validated to be available by checking the
reference manual back to i.MX25.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
---
drivers/mci/imx-esdhc.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/mci/imx-esdhc.c b/drivers/mci/imx-esdhc.c
index c4daa9d12136..db96a813971a 100644
--- a/drivers/mci/imx-esdhc.c
+++ b/drivers/mci/imx-esdhc.c
@@ -455,10 +455,13 @@ static void set_sysctl(struct mci_host *mci, u32 clock)
wait_on_timeout(10 * MSECOND,
esdhc_read32(regs + SDHCI_PRESENT_STATE) & PRSSTAT_SDSTB);
- clk = SYSCTL_PEREN | SYSCTL_CKEN;
+ clk = SYSCTL_PEREN | SYSCTL_CKEN | SYSCTL_INITA;
esdhc_setbits32(regs + SDHCI_CLOCK_CONTROL__TIMEOUT_CONTROL__SOFTWARE_RESET,
clk);
+
+ wait_on_timeout(1 * MSECOND,
+ !(esdhc_read32(regs + SDHCI_CLOCK_CONTROL) & SYSCTL_INITA));
}
static void esdhc_set_ios(struct mci_host *mci, struct mci_ios *ios)
--
2.18.0
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next reply other threads:[~2018-07-25 9:57 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-25 9:57 Lucas Stach [this message]
2018-08-08 6:35 ` Sascha Hauer
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