Re: [PATCH v2 4/4] mmc: sdhci-brcmstb: Add ability to increase max clock rate for 72116b0

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On 4/27/22 11:08, 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, "clock-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 | 25 +++++++++++++++++++++++++
  1 file changed, 25 insertions(+)

diff --git a/drivers/mmc/host/sdhci-brcmstb.c b/drivers/mmc/host/sdhci-brcmstb.c
index 683d0c685748..51a23e9f4535 100644
--- a/drivers/mmc/host/sdhci-brcmstb.c
+++ b/drivers/mmc/host/sdhci-brcmstb.c
@@ -250,6 +250,7 @@ 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;
+	u32 base_clock_hz = 0;
  	struct sdhci_host *host;
  	struct resource *iomem;
  	struct clk *clk;
@@ -330,6 +331,30 @@ 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 (device_property_read_u32(&pdev->dev, "max-frequency",
+				     &base_clock_hz) == 0) {
+		struct clk *master_clk;
+		u32 actual_clock_mhz;
+
+		master_clk = devm_clk_get(&pdev->dev, "sdio_freq");
+		if (IS_ERR(master_clk)) {
+			dev_warn(&pdev->dev,
+				 "Clock for \"sdio_freq\" was not found\n");
+		} else {
+			clk_set_rate(master_clk, base_clock_hz);

It seems to me that you should enable the clock before getting its rate, otherwise this may not return a valid rate. You might also consider reducing the indentation a little bit by using a label.
--
Florian



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