linux-kernel - [PATCH] mmc: sdhci-of-esdhc: Don't walk device-tree on every interrupt

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Message-Id: <20200902040623.17509-1-chris.packham@alliedtelesis.co.nz>
Date:   Wed,  2 Sep 2020 16:06:23 +1200
From:   Chris Packham <chris.packham@...iedtelesis.co.nz>
To:     adrian.hunter@...el.com, ulf.hansson@...aro.org
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chris Packham <chris.packham@...iedtelesis.co.nz>
Subject: [PATCH] mmc: sdhci-of-esdhc: Don't walk device-tree on every interrupt

Commit b214fe592ab7 ("mmc: sdhci-of-esdhc: add erratum eSDHC7 support")
added code to check for a specific compatible string in the device-tree
on every esdhc interrupt. We know that if it's present the compatible
string will be found on the sdhc host. Instead of walking the
device-tree, go directly to the sdhc host's device and use
of_device_is_compatible().

Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
---

I found this in passing while trying to track down another issue using ftrace.
I found it odd that I was seeing a lot of calls to __of_device_is_compatible()
coming from esdhc_irq() (the fact that this interrupt is going off on my board
is also odd, but that's a different story).

 drivers/mmc/host/sdhci-of-esdhc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/host/sdhci-of-esdhc.c b/drivers/mmc/host/sdhci-of-esdhc.c
index 7c73d243dc6c..11c8c522d623 100644
--- a/drivers/mmc/host/sdhci-of-esdhc.c
+++ b/drivers/mmc/host/sdhci-of-esdhc.c
@@ -1177,10 +1177,11 @@ static void esdhc_set_uhs_signaling(struct sdhci_host *host,

 static u32 esdhc_irq(struct sdhci_host *host, u32 intmask)
 {
+	struct device *dev = mmc_dev(host->mmc);
+	struct device_node *np = dev->of_node;
 	u32 command;

-	if (of_find_compatible_node(NULL, NULL,
-				"fsl,p2020-esdhc")) {
+	if (of_device_is_compatible(np, "fsl,p2020-esdhc")) {
 		command = SDHCI_GET_CMD(sdhci_readw(host,
 					SDHCI_COMMAND));
 		if (command == MMC_WRITE_MULTIPLE_BLOCK &&
-- 
2.28.0