Re: [PATCH v2 2/2] mmc: sdhci-brcmstb: Add ability to increase max clock rate for 72116b0

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Hi Kamal,

On 5/17/2022 11:04 AM, Kamal Dasu wrote:
From: Al Cooper <alcooperx@xxxxxxxxx>

The 72116B0 has improved SDIO controllers that allow the max clock
rate to be increased from a max of 100MHz to a max of 150MHz. The
driver will need to get the clock and increase it's default rate
and override the caps register, that still indicates a max of 100MHz.
The new clock will be named "sdio_freq" in the DT node's "clock-names"
list. The driver will use a DT property, "max-frequency", to
enable this functionality and will get the actual rate in MHz
from the property to allow various speeds to be requested.

Signed-off-by: Al Cooper <alcooperx@xxxxxxxxx>
Signed-off-by: Kamal Dasu <kdasu.kdev@xxxxxxxxx>
---
  drivers/mmc/host/sdhci-brcmstb.c | 28 ++++++++++++++++++++++++++++
  1 file changed, 28 insertions(+)

diff --git a/drivers/mmc/host/sdhci-brcmstb.c b/drivers/mmc/host/sdhci-brcmstb.c
index 8eb57de48e0c..bb614a5e1ea4 100644
--- a/drivers/mmc/host/sdhci-brcmstb.c
+++ b/drivers/mmc/host/sdhci-brcmstb.c
@@ -250,6 +250,8 @@ static int sdhci_brcmstb_probe(struct platform_device *pdev)
  	struct sdhci_pltfm_host *pltfm_host;
  	const struct of_device_id *match;
  	struct sdhci_brcmstb_priv *priv;
+	struct clk *master_clk;
+	u32 actual_clock_mhz;
  	struct sdhci_host *host;
  	struct resource *iomem;
  	struct clk *clk;
@@ -330,6 +332,32 @@ static int sdhci_brcmstb_probe(struct platform_device *pdev)
  	if (match_priv->flags & BRCMSTB_MATCH_FLAGS_BROKEN_TIMEOUT)
  		host->quirks |= SDHCI_QUIRK_BROKEN_TIMEOUT_VAL;
+ /* Change the base clock frequency if the DT property exists */
+	if (!(host->mmc->f_max))
+		goto add_host;
+
+	master_clk = devm_clk_get(&pdev->dev, "sdio_freq");

This looks like a candidate for devm_clk_get_optional() since the clock is optional. Then you can call clk_prepare_enable() unconditionally even if it is NULL/non-existent.

+	if (IS_ERR(master_clk)) {
+		dev_warn(&pdev->dev, "Clock for \"sdio_freq\" not found\n");
+		goto add_host;
+	} else {
+		res = clk_prepare_enable(master_clk);
+		if (res)
+			goto err;

It looks like we may be leaving the clock enabled even when we did not want to (e.g.: error path) and do not we need to turn if off, respectively turn it back on in .suspend() and .resume()?

+	}
+
+	/* set improved clock rate */
+	clk_set_rate(master_clk, host->mmc->f_max);
+	actual_clock_mhz = clk_get_rate(master_clk) / 1000000;
+
+	host->caps &= ~SDHCI_CLOCK_V3_BASE_MASK;
+	host->caps |= (actual_clock_mhz << SDHCI_CLOCK_BASE_SHIFT);
+	/* Disable presets because they are now incorrect */
+	host->quirks2 |= SDHCI_QUIRK2_PRESET_VALUE_BROKEN;
+	dev_dbg(&pdev->dev, "Base Clock Frequency changed to %dMHz\n",
+		actual_clock_mhz);
+
+add_host:
  	res = sdhci_brcmstb_add_host(host, priv);
  	if (res)
  		goto err;

It looks like we would need to unwind the clk_prepare_enable(master_clk) in case of failures here.
--
Florian



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