linux-kernel - Re: [RFC v2 2/2] mmc: sdhci: Ignore capability register when it comes to speeds and use DT binding instead when sdhci-cap-speed-modes-broken is set.

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Date:   Mon, 24 Oct 2016 10:34:46 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Zach Brown <zach.brown@...com>, ulf.hansson@...aro.org
Cc:     robh+dt@...nel.org, mark.rutland@....com,
        linux-mmc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 2/2] mmc: sdhci: Ignore capability register when it comes
 to speeds and use DT binding instead when sdhci-cap-speed-modes-broken is
 set.

On 22/10/16 00:35, Zach Brown wrote:
> When the sdhci-cap-speed-modes-broken DT property is set, the driver
> will ignore the bits of the capability registers that correspond to
> speed modes.
> 
> Signed-off-by: Zach Brown <zach.brown@...com>
> ---
>  drivers/mmc/host/sdhci.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 1e25b01..59c62d3 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -22,6 +22,7 @@
>  #include <linux/scatterlist.h>
>  #include <linux/regulator/consumer.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/of.h>
>  
>  #include <linux/leds.h>
>  
> @@ -3013,10 +3014,19 @@ void __sdhci_read_caps(struct sdhci_host *host, u16 *ver, u32 *caps, u32 *caps1)
>  
>  	host->caps = caps ? *caps : sdhci_readl(host, SDHCI_CAPABILITIES);
>  
> +	if (of_property_read_bool(mmc_dev(host->mmc)->of_node,
> +				  "sdhci-cap-speed-modes-broken"))

It rather begs the question: if you are going to do something sdhci
specific, why not just read the whole of the caps register from DT?

> +		host->caps &= ~SDHCI_CAN_DO_HISPD;
> +
>  	if (host->version < SDHCI_SPEC_300)
>  		return;
>  
>  	host->caps1 = caps1 ? *caps1 : sdhci_readl(host, SDHCI_CAPABILITIES_1);
> +
> +	if (of_property_read_bool(mmc_dev(host->mmc)->of_node,
> +				  "sdhci-cap-speed-modes-broken"))

Why read it twice?

> +		host->caps1 &= ~(SDHCI_SUPPORT_SDR50 | SDHCI_SUPPORT_SDR104 |
> +				 SDHCI_SUPPORT_DDR50 | SDHCI_SUPPORT_HS400);
>  }
>  EXPORT_SYMBOL_GPL(__sdhci_read_caps);
>  
>