linux-kernel - [PATCH V2] mmc: pwrseq_simple: Handle !RESET

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Message-Id: <20241108130647.8281-1-wahrenst@gmx.net>
Date: Fri,  8 Nov 2024 14:06:47 +0100
From: Stefan Wahren <wahrenst@....net>
To: Philipp Zabel <p.zabel@...gutronix.de>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Marco Felsch <m.felsch@...gutronix.de>,
	Catalin Popescu <catalin.popescu@...ca-geosystems.com>
Cc: Florian Fainelli <florian.fainelli@...adcom.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Stefan Wahren <wahrenst@....net>
Subject: [PATCH V2] mmc: pwrseq_simple: Handle !RESET_CONTROLLER properly

The recent introduction of reset control in pwrseq_simple introduced
a regression for platforms without RESET_CONTROLLER support, because
devm_reset_control_get_optional_shared() would return NULL and make all
resets no-ops. Instead of enforcing this dependency, rely on this behavior
to determine reset support. As a benefit we can get the rid of the
use_reset flag.

Fixes: 73bf4b7381f7 ("mmc: pwrseq_simple: add support for one reset control")
Signed-off-by: Stefan Wahren <wahrenst@....net>
---
 drivers/mmc/core/pwrseq_simple.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

Changes in V2:
- add explaining comment as suggested by Marco Felsch

diff --git a/drivers/mmc/core/pwrseq_simple.c b/drivers/mmc/core/pwrseq_simple.c
index 24e4e63a5dc8..37cd858df0f4 100644
--- a/drivers/mmc/core/pwrseq_simple.c
+++ b/drivers/mmc/core/pwrseq_simple.c
@@ -32,7 +32,6 @@ struct mmc_pwrseq_simple {
 	struct clk *ext_clk;
 	struct gpio_descs *reset_gpios;
 	struct reset_control *reset_ctrl;
-	bool use_reset;
 };

 #define to_pwrseq_simple(p) container_of(p, struct mmc_pwrseq_simple, pwrseq)
@@ -71,7 +70,7 @@ static void mmc_pwrseq_simple_pre_power_on(struct mmc_host *host)
 		pwrseq->clk_enabled = true;
 	}

-	if (pwrseq->use_reset) {
+	if (pwrseq->reset_ctrl) {
 		reset_control_deassert(pwrseq->reset_ctrl);
 		reset_control_assert(pwrseq->reset_ctrl);
 	} else
@@ -82,7 +81,7 @@ static void mmc_pwrseq_simple_post_power_on(struct mmc_host *host)
 {
 	struct mmc_pwrseq_simple *pwrseq = to_pwrseq_simple(host->pwrseq);

-	if (pwrseq->use_reset)
+	if (pwrseq->reset_ctrl)
 		reset_control_deassert(pwrseq->reset_ctrl);
 	else
 		mmc_pwrseq_simple_set_gpios_value(pwrseq, 0);
@@ -95,7 +94,7 @@ static void mmc_pwrseq_simple_power_off(struct mmc_host *host)
 {
 	struct mmc_pwrseq_simple *pwrseq = to_pwrseq_simple(host->pwrseq);

-	if (pwrseq->use_reset)
+	if (pwrseq->reset_ctrl)
 		reset_control_assert(pwrseq->reset_ctrl);
 	else
 		mmc_pwrseq_simple_set_gpios_value(pwrseq, 1);
@@ -137,15 +136,18 @@ static int mmc_pwrseq_simple_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, PTR_ERR(pwrseq->ext_clk), "external clock not ready\n");

 	ngpio = of_count_phandle_with_args(dev->of_node, "reset-gpios", "#gpio-cells");
-	if (ngpio == 1)
-		pwrseq->use_reset = true;
-
-	if (pwrseq->use_reset) {
+	if (ngpio == 1) {
 		pwrseq->reset_ctrl = devm_reset_control_get_optional_shared(dev, NULL);
 		if (IS_ERR(pwrseq->reset_ctrl))
 			return dev_err_probe(dev, PTR_ERR(pwrseq->reset_ctrl),
 					     "reset control not ready\n");
-	} else {
+	}
+
+	/*
+	 * Fallback to GPIO based reset control in case of multiple reset lines
+	 * are specified or the platform doesn't have support for RESET at all.
+	 */
+	if (!pwrseq->reset_ctrl) {
 		pwrseq->reset_gpios = devm_gpiod_get_array(dev, "reset", GPIOD_OUT_HIGH);
 		if (IS_ERR(pwrseq->reset_gpios) &&
 		    PTR_ERR(pwrseq->reset_gpios) != -ENOENT &&
--
2.34.1