[PATCH 4.14 158/161] mmc: sdhci-of-esdhc: Revert "mmc: sdhci-of-esdhc: add erratum A-009204 support"

Greg Kroah-Hartman
2019-12-29T17:27:30Z

From: Rasmus Villemoes <linux@rasmusvillemoes.dk>

commit 8b6dc6b2d60221e90703babbc141f063b8a07e72 upstream.

This reverts commit 5dd195522562542bc6ebe6e7bd47890d8b7ca93c.

First, the fix seems to be plain wrong, since the erratum suggests
waiting 5ms before setting setting SYSCTL[RSTD], but this msleep()
happens after the call of sdhci_reset() which is where that bit gets
set (if SDHCI_RESET_DATA is in mask).

Second, walking the whole device tree to figure out if some node has a
"fsl,p2020-esdhc" compatible string is hugely expensive - about 70 to
100 us on our mpc8309 board. Walking the device tree is done under a
raw_spin_lock, so this is obviously really bad on an -rt system, and a
waste of time on all.

In fact, since esdhc_reset() seems to get called around 100 times per
second, that mpc8309 now spends 0.8% of its time determining that
it is not a p2020. Whether those 100 calls/s are normal or due to some
other bug or misconfiguration, regularly hitting a 100 us
non-preemptible window is unacceptable.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20191204085447.27491-1-linux@rasmusvillemoes.dk
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/mmc/host/sdhci-of-esdhc.c | 3 ---
1 file changed, 3 deletions(-)

--- a/drivers/mmc/host/sdhci-of-esdhc.c
+++ b/drivers/mmc/host/sdhci-of-esdhc.c
@@ -615,9 +615,6 @@ static void esdhc_reset(struct sdhci_hos
sdhci_writel(host, host->ier, SDHCI_INT_ENABLE);
sdhci_writel(host, host->ier, SDHCI_SIGNAL_ENABLE);

- if (of_find_compatible_node(NULL, NULL, "fsl,p2020-esdhc"))
- mdelay(5);
-
if (mask & SDHCI_RESET_ALL) {
val = sdhci_readl(host, ESDHC_TBCTL);
val &= ~ESDHC_TB_EN;