linux-kernel - Re: [PATCH V5 3/3] spi: spi-geni-qcom: Add SPI driver support for GENI based QUP

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Message-ID: <153911433511.119890.17831207059115471972@swboyd.mtv.corp.google.com>
Date:   Tue, 09 Oct 2018 12:45:35 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Doug Anderson <dianders@...omium.org>
Cc:     alokc@...eaurora.org, Mark Brown <broonie@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-spi <linux-spi@...r.kernel.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Girish Mahadevan <girishm@...eaurora.org>,
        Dilip Kota <dkota@...eaurora.org>
Subject: Re: [PATCH V5 3/3] spi: spi-geni-qcom: Add SPI driver support for GENI based
 QUP

Quoting Doug Anderson (2018-10-09 10:48:55)
> 
> Ah, you're suggesting separating the platform_get_irq() and the
> request_irq() so that we call platform_get_irq() as the first thing in
> the function but don't do the request_irq() until later.  Yeah, that
> could be done and I guess if you feel strongly about it I wouldn't
> object to the change, but I don't feel it buys us a lot and I kind of
> like keeping the two next to each other.  Specifically why I don't
> think it buys us a lot:
> 
> 1. You still need the "dev_err" print, right?  platform_get_irq()
> doesn't automatically print errors for you I think.

I usually leave it out. Who cares? Maybe we should throw a dev_err()
into platform_get_irq() on failure so we can keep drivers cleaner and
reduce a bunch of "can't find my IRQ" messages throughout the kernel.

> 
> 2. You now need a local variable "irq".  By putting the
> platform_get_irq() before the memory allocation you now can't store it
> directly in mas->irq.  We could try using "ret" as a temporary
> variable but that seems worse in this case since it'd be a bit
> fragile.
> 
> 3. You don't get rid of any error labels / error handling so we don't
> really save any code
> 
> When I tried this my diffstat says 8 lines added and 7 removed, so a
> net increase in LOC FWIW.  I'm relying in gmail so my patch will be
> whitespace-damaged (sigh), but you can find a clean one at:
> 
> https://chromium.googlesource.com/chromiumos/third_party/kernel/+/e0325d618e209c22379e3a4269c14627b19243a8%5E%21/#F0
> 
> ...the basic idea is this though:
> 

Thanks! Here's an updated patch that I haven't compile tested in any way
that hoists up the IO mapping part too, which shows that the 'se' local
variable is almost entirely useless.

 drivers/spi/spi-geni-qcom.c | 49 ++++++++++++++++++++++-----------------------
 1 file changed, 24 insertions(+), 25 deletions(-)

diff --git a/drivers/spi/spi-geni-qcom.c b/drivers/spi/spi-geni-qcom.c
index 6432ecc4e2ca..917707448578 100644
--- a/drivers/spi/spi-geni-qcom.c
+++ b/drivers/spi/spi-geni-qcom.c
@@ -538,11 +538,30 @@ static irqreturn_t geni_spi_isr(int irq, void *data)
 
 static int spi_geni_probe(struct platform_device *pdev)
 {
-	int ret;
+	int ret, irq;
 	struct spi_master *spi;
 	struct spi_geni_master *mas;
 	struct resource *res;
-	struct geni_se *se;
+	void __iomem *base;
+	struct clk *clk;
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_err(&pdev->dev, "Err getting IRQ %d\n", irq);
+		return irq;
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	clk = devm_clk_get(&pdev->dev, "se");
+	if (IS_ERR(clk)) {
+		ret = PTR_ERR(mas->se.clk);
+		dev_err(&pdev->dev, "Err getting SE Core clk %d\n", ret);
+		return ret;
+	}
 
 	spi = spi_alloc_master(&pdev->dev, sizeof(*mas));
 	if (!spi)
@@ -550,27 +569,15 @@ static int spi_geni_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, spi);
 	mas = spi_master_get_devdata(spi);
+	mas->irq = irq;
 	mas->dev = &pdev->dev;
 	mas->se.dev = &pdev->dev;
 	mas->se.wrapper = dev_get_drvdata(pdev->dev.parent);
-	se = &mas->se;
+	mas->se.base = base;
+	mas->se.clk = clk;
 
 	spi->bus_num = -1;
 	spi->dev.of_node = pdev->dev.of_node;
-	mas->se.clk = devm_clk_get(&pdev->dev, "se");
-	if (IS_ERR(mas->se.clk)) {
-		ret = PTR_ERR(mas->se.clk);
-		dev_err(&pdev->dev, "Err getting SE Core clk %d\n", ret);
-		goto spi_geni_probe_err;
-	}
-
-	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	se->base = devm_ioremap_resource(&pdev->dev, res);
-	if (IS_ERR(se->base)) {
-		ret = PTR_ERR(se->base);
-		goto spi_geni_probe_err;
-	}
-
 	spi->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LOOP | SPI_CS_HIGH;
 	spi->bits_per_word_mask = SPI_BPW_RANGE_MASK(4, 32);
 	spi->num_chipselect = 4;
@@ -589,13 +596,6 @@ static int spi_geni_probe(struct platform_device *pdev)
 	if (ret)
 		goto spi_geni_probe_runtime_disable;
 
-	mas->irq = platform_get_irq(pdev, 0);
-	if (mas->irq < 0) {
-		ret = mas->irq;
-		dev_err(&pdev->dev, "Err getting IRQ %d\n", ret);
-		goto spi_geni_probe_runtime_disable;
-	}
-
 	ret = request_irq(mas->irq, geni_spi_isr,
 			IRQF_TRIGGER_HIGH, "spi_geni", spi);
 	if (ret)
@@ -610,7 +610,6 @@ static int spi_geni_probe(struct platform_device *pdev)
 	free_irq(mas->irq, spi);
 spi_geni_probe_runtime_disable:
 	pm_runtime_disable(&pdev->dev);
-spi_geni_probe_err:
 	spi_master_put(spi);
 	return ret;
 }