[PATCH 0/3] hwrng: xgene - Some improvements

[PATCH 0/3] hwrng: xgene - Some improvements

[Uwe Kleine-König]

Hello,

while working on the quest to make struct platform_driver::remove() return void
I stumbled over the xgene-rng driver because it didn't return 0 in .remove().

Looking at it I found two other patch opportunities, here is the result.

I think the driver has some more problems:

 - device_init_wakeup() is only called after devm_hwrng_register(). After the
   latter returns the respective callbacks can be called. Is the device already
   in the right state before device_init_wakeup(..., 1)?

 - Similar problem on .remove(): device_init_wakeup(..., 0) is called before
   hwrng_unregister() happens.

 - If there are two (or more) devices of that type, .probe() for the 2nd overwrites
   xgene_rng_func.priv of the first one.

Best regards
Uwe

Uwe Kleine-König (3):
  hwrng: xgene - Simplify using dev_err_probe()
  hwrng: xgene - Simplify using devm_clk_get_optional_enabled()
  hwrng: xgene - Improve error reporting for problems during .remove()

 drivers/char/hw_random/xgene-rng.c | 44 ++++++++----------------------
 1 file changed, 11 insertions(+), 33 deletions(-)

base-commit: e05dec85e78317f251eddd27e0357b2253d9dfc4
-- 
2.39.1

[PATCH 1/3] hwrng: xgene - Simplify using dev_err_probe()

[Uwe Kleine-König]

dev_err_probe simplifies the idiom:

	if (ret != -EPROBE_DEFER)
		dev_err(...)
	return ret;

, emits the error code in a human readable way and even yields a useful
entry in /sys/kernel/debug/devices_deferred in the EPROBE_DEFER case.

So simplify and at the same time improve the driver by using
dev_err_probe().

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
 drivers/char/hw_random/xgene-rng.c | 21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/drivers/char/hw_random/xgene-rng.c b/drivers/char/hw_random/xgene-rng.c
index 008e6db9ce01..a6a30686a58b 100644
--- a/drivers/char/hw_random/xgene-rng.c
+++ b/drivers/char/hw_random/xgene-rng.c
@@ -337,10 +337,8 @@ static int xgene_rng_probe(struct platform_device *pdev)
 
 	rc = devm_request_irq(&pdev->dev, ctx->irq, xgene_rng_irq_handler, 0,
 				dev_name(&pdev->dev), ctx);
-	if (rc) {
-		dev_err(&pdev->dev, "Could not request RNG alarm IRQ\n");
-		return rc;
-	}
+	if (rc)
+		return dev_err_probe(&pdev->dev, rc, "Could not request RNG alarm IRQ\n");
 
 	/* Enable IP clock */
 	ctx->clk = devm_clk_get(&pdev->dev, NULL);
@@ -348,30 +346,25 @@ static int xgene_rng_probe(struct platform_device *pdev)
 		dev_warn(&pdev->dev, "Couldn't get the clock for RNG\n");
 	} else {
 		rc = clk_prepare_enable(ctx->clk);
-		if (rc) {
-			dev_warn(&pdev->dev,
-				 "clock prepare enable failed for RNG");
-			return rc;
-		}
+		if (rc)
+			return dev_err_probe(&pdev->dev, rc,
+					     "clock prepare enable failed for RNG");
 	}
 
 	xgene_rng_func.priv = (unsigned long) ctx;
 
 	rc = devm_hwrng_register(&pdev->dev, &xgene_rng_func);
 	if (rc) {
-		dev_err(&pdev->dev, "RNG registering failed error %d\n", rc);
 		if (!IS_ERR(ctx->clk))
 			clk_disable_unprepare(ctx->clk);
-		return rc;
+		return dev_err_probe(&pdev->dev, rc, "RNG registering failed\n");
 	}
 
 	rc = device_init_wakeup(&pdev->dev, 1);
 	if (rc) {
-		dev_err(&pdev->dev, "RNG device_init_wakeup failed error %d\n",
-			rc);
 		if (!IS_ERR(ctx->clk))
 			clk_disable_unprepare(ctx->clk);
-		return rc;
+		return dev_err_probe(&pdev->dev, rc, "RNG device_init_wakeup failed\n");
 	}
 
 	return 0;
-- 
2.39.1

[PATCH 2/3] hwrng: xgene - Simplify using devm_clk_get_optional_enabled()

[Uwe Kleine-König]

Instead of ignoring errors returned by devm_clk_get() and manually
enabling the clk for the whole lifetime of the bound device, use
devm_clk_get_optional_enabled(). This is simpler and also more correct
as it doesn't ignore errors. This is also more correct because now the
call to clk_disable_unprepare() can be dropped from xgene_rng_remove()
which happened while the hwrn device was still registered. With the devm
callback disabling the clk happens correctly only after
devm_hwrng_register() is undone.

As a result struct xgene_rng_dev::clk is only used in xgene_rng_probe, and
so the struct member can be replaced by a local variable.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
 drivers/char/hw_random/xgene-rng.c | 27 ++++++---------------------
 1 file changed, 6 insertions(+), 21 deletions(-)

diff --git a/drivers/char/hw_random/xgene-rng.c b/drivers/char/hw_random/xgene-rng.c
index a6a30686a58b..31662614a48f 100644
--- a/drivers/char/hw_random/xgene-rng.c
+++ b/drivers/char/hw_random/xgene-rng.c
@@ -84,7 +84,6 @@ struct xgene_rng_dev {
 	unsigned long failure_ts;/* First failure timestamp */
 	struct timer_list failure_timer;
 	struct device *dev;
-	struct clk *clk;
 };
 
 static void xgene_rng_expired_timer(struct timer_list *t)
@@ -314,6 +313,7 @@ static struct hwrng xgene_rng_func = {
 static int xgene_rng_probe(struct platform_device *pdev)
 {
 	struct xgene_rng_dev *ctx;
+	struct clk *clk;
 	int rc = 0;
 
 	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
@@ -341,45 +341,30 @@ static int xgene_rng_probe(struct platform_device *pdev)
 		return dev_err_probe(&pdev->dev, rc, "Could not request RNG alarm IRQ\n");
 
 	/* Enable IP clock */
-	ctx->clk = devm_clk_get(&pdev->dev, NULL);
-	if (IS_ERR(ctx->clk)) {
-		dev_warn(&pdev->dev, "Couldn't get the clock for RNG\n");
-	} else {
-		rc = clk_prepare_enable(ctx->clk);
-		if (rc)
-			return dev_err_probe(&pdev->dev, rc,
-					     "clock prepare enable failed for RNG");
-	}
+	clk = devm_clk_get_optional_enabled(&pdev->dev, NULL);
+	if (IS_ERR(clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(clk), "Couldn't get the clock for RNG\n");
 
 	xgene_rng_func.priv = (unsigned long) ctx;
 
 	rc = devm_hwrng_register(&pdev->dev, &xgene_rng_func);
-	if (rc) {
-		if (!IS_ERR(ctx->clk))
-			clk_disable_unprepare(ctx->clk);
+	if (rc)
 		return dev_err_probe(&pdev->dev, rc, "RNG registering failed\n");
-	}
 
 	rc = device_init_wakeup(&pdev->dev, 1);
-	if (rc) {
-		if (!IS_ERR(ctx->clk))
-			clk_disable_unprepare(ctx->clk);
+	if (rc)
 		return dev_err_probe(&pdev->dev, rc, "RNG device_init_wakeup failed\n");
-	}
 
 	return 0;
 }
 
 static int xgene_rng_remove(struct platform_device *pdev)
 {
-	struct xgene_rng_dev *ctx = platform_get_drvdata(pdev);
 	int rc;
 
 	rc = device_init_wakeup(&pdev->dev, 0);
 	if (rc)
 		dev_err(&pdev->dev, "RNG init wakeup failed error %d\n", rc);
-	if (!IS_ERR(ctx->clk))
-		clk_disable_unprepare(ctx->clk);
 
 	return rc;
 }
-- 
2.39.1

[PATCH 3/3] hwrng: xgene - Improve error reporting for problems during .remove()

[Uwe Kleine-König]

Returning an error value in a platform driver's remove callback results in
a generic error message being emitted by the driver core, but otherwise it
doesn't make a difference. The device goes away anyhow.

As the driver already emits a better error message than the core, suppress
the generic error message by returning zero unconditionally.
---
 drivers/char/hw_random/xgene-rng.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/hw_random/xgene-rng.c b/drivers/char/hw_random/xgene-rng.c
index 31662614a48f..c67d3185b5b6 100644
--- a/drivers/char/hw_random/xgene-rng.c
+++ b/drivers/char/hw_random/xgene-rng.c
@@ -366,7 +366,7 @@ static int xgene_rng_remove(struct platform_device *pdev)
 	if (rc)
 		dev_err(&pdev->dev, "RNG init wakeup failed error %d\n", rc);
 
-	return rc;
+	return 0;
 }
 
 static const struct of_device_id xgene_rng_of_match[] = {
-- 
2.39.1

Re: [PATCH 0/3] hwrng: xgene - Some improvements

[Herbert Xu]

On Tue, Feb 14, 2023 at 05:28:26PM +0100, Uwe Kleine-König wrote:
> Hello,
> 
> while working on the quest to make struct platform_driver::remove() return void
> I stumbled over the xgene-rng driver because it didn't return 0 in .remove().
> 
> Looking at it I found two other patch opportunities, here is the result.
> 
> I think the driver has some more problems:
> 
>  - device_init_wakeup() is only called after devm_hwrng_register(). After the
>    latter returns the respective callbacks can be called. Is the device already
>    in the right state before device_init_wakeup(..., 1)?
> 
>  - Similar problem on .remove(): device_init_wakeup(..., 0) is called before
>    hwrng_unregister() happens.
> 
>  - If there are two (or more) devices of that type, .probe() for the 2nd overwrites
>    xgene_rng_func.priv of the first one.
> 
> Best regards
> Uwe
> 
> Uwe Kleine-König (3):
>   hwrng: xgene - Simplify using dev_err_probe()
>   hwrng: xgene - Simplify using devm_clk_get_optional_enabled()
>   hwrng: xgene - Improve error reporting for problems during .remove()
> 
>  drivers/char/hw_random/xgene-rng.c | 44 ++++++++----------------------
>  1 file changed, 11 insertions(+), 33 deletions(-)
> 
> base-commit: e05dec85e78317f251eddd27e0357b2253d9dfc4
> -- 
> 2.39.1

All applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH 3/3] hwrng: xgene - Improve error reporting for problems during .remove()

[Uwe Kleine-König]

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Hello,

On Tue, Feb 14, 2023 at 05:28:29PM +0100, Uwe Kleine-König wrote:
> Returning an error value in a platform driver's remove callback results in
> a generic error message being emitted by the driver core, but otherwise it
> doesn't make a difference. The device goes away anyhow.
> 
> As the driver already emits a better error message than the core, suppress
> the generic error message by returning zero unconditionally.

I forgot to add a S-o-b line here. Stephen Rothwell pointed that out for
the applied patch in next.

I don't know how/if Herbert will fix this, but for the Record:

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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Re: [PATCH 3/3] hwrng: xgene - Improve error reporting for problems during .remove()

[Herbert Xu]

On Tue, Mar 14, 2023 at 10:04:09AM +0100, Uwe Kleine-König wrote:
>
> I don't know how/if Herbert will fix this, but for the Record:
> 
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

I've fixed it in my tree.  Thanks!
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt