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

[Florian Fainelli <f.fainelli@gmail.com>]

On 4/27/22 11:08, Kamal Dasu wrote:
> From: Al Cooper <alcooperx@gmail.com>
> 
> 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@gmail.com>
> Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
> ---
>   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