[PATCH] ARC: [plat-hsdk]: Increase SDIO CIU frequency to 50000000Hz

[PATCH] ARC: [plat-hsdk]: Increase SDIO CIU frequency to 50000000Hz

[Eugeniy Paltsev]

With current SDIO CIU clock frequency (12500000Hz) DW MMC
controller fails to initialize some SD cards (which don't
support slow mode).

So increase SDIO CIU frequency from 12500000Hz to 50000000Hz by
switching from the default divisor value (div-by-8) to the
minimum possible value of the divisor (div-by-2) in HSDK platform
code.

Reported-by: Vineet Gupta <vgupta@synopsys.com>
Tested-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
---
 arch/arc/boot/dts/hsdk.dts    | 11 ++++++-----
 arch/arc/plat-hsdk/platform.c | 10 ++++++++++
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/arch/arc/boot/dts/hsdk.dts b/arch/arc/boot/dts/hsdk.dts
index 8adde1b..8f627c2 100644
--- a/arch/arc/boot/dts/hsdk.dts
+++ b/arch/arc/boot/dts/hsdk.dts
@@ -137,14 +137,15 @@
 			/*
 			 * DW sdio controller has external ciu clock divider
 			 * controlled via register in SDIO IP. Due to its
-			 * unexpected default value (it should devide by 1
-			 * but it devides by 8) SDIO IP uses wrong clock and
+			 * unexpected default value (it should divide by 1
+			 * but it divides by 8) SDIO IP uses wrong clock and
 			 * works unstable (see STAR 9001204800)
+			 * We switched to the minimum possible value of the
+			 * divisor (div-by-2) in HSDK platform code.
 			 * So add temporary fix and change clock frequency
-			 * from 100000000 to 12500000 Hz until we fix dw sdio
-			 * driver itself.
+			 * to 50000000 Hz until we fix dw sdio driver itself.
 			 */
-			clock-frequency = <12500000>;
+			clock-frequency = <50000000>;
 			#clock-cells = <0>;
 		};
 
diff --git a/arch/arc/plat-hsdk/platform.c b/arch/arc/plat-hsdk/platform.c
index 744e62e..5ea46b6 100644
--- a/arch/arc/plat-hsdk/platform.c
+++ b/arch/arc/plat-hsdk/platform.c
@@ -74,6 +74,10 @@ static void __init hsdk_set_cpu_freq_1ghz(void)
 		pr_err("Failed to setup CPU frequency to 1GHz!");
 }
 
+#define SDIO_BASE		(ARC_PERIPHERAL_BASE + 0xA000)
+#define SDIO_UHS_REG_EXT	(SDIO_BASE + 0x108)
+#define SDIO_UHS_REG_EXT_DIV_2	(2 << 30)
+
 static void __init hsdk_init_early(void)
 {
 	/*
@@ -89,6 +93,12 @@ static void __init hsdk_init_early(void)
 	/* Really apply settings made above */
 	writel(1, (void __iomem *) CREG_PAE_UPDATE);
 
+	/* 
+	 * Switch SDIO external ciu clock divider from default div-by-8 to
+	 * minimum possible div-by-2.
+	 */
+	iowrite32(SDIO_UHS_REG_EXT_DIV_2, (void __iomem *) SDIO_UHS_REG_EXT);
+
 	/*
 	 * Setup CPU frequency to 1GHz.
 	 * TODO: remove it after smart hsdk pll driver will be introduced.
-- 
2.9.3

Re: [PATCH] ARC: [plat-hsdk]: Increase SDIO CIU frequency to 50000000Hz

[Vineet Gupta]

On 10/11/2017 10:01 AM, Eugeniy Paltsev wrote:
> With current SDIO CIU clock frequency (12500000Hz) DW MMC
> controller fails to initialize some SD cards (which don't
> support slow mode).
>
> So increase SDIO CIU frequency from 12500000Hz to 50000000Hz by
> switching from the default divisor value (div-by-8) to the
> minimum possible value of the divisor (div-by-2) in HSDK platform
> code.
>
> Reported-by: Vineet Gupta <vgupta@synopsys.com>
> Tested-by: Vineet Gupta <vgupta@synopsys.com>
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>

Thx for the quick fix - I've applied it- minor nit below !

> ---
>   arch/arc/boot/dts/hsdk.dts    | 11 ++++++-----
>   arch/arc/plat-hsdk/platform.c | 10 ++++++++++
>   2 files changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arc/boot/dts/hsdk.dts b/arch/arc/boot/dts/hsdk.dts
> index 8adde1b..8f627c2 100644
> --- a/arch/arc/boot/dts/hsdk.dts
> +++ b/arch/arc/boot/dts/hsdk.dts
> @@ -137,14 +137,15 @@
>   			/*
>   			 * DW sdio controller has external ciu clock divider
>   			 * controlled via register in SDIO IP. Due to its
> -			 * unexpected default value (it should devide by 1
> -			 * but it devides by 8) SDIO IP uses wrong clock and
> +			 * unexpected default value (it should divide by 1
> +			 * but it divides by 8) SDIO IP uses wrong clock and
>   			 * works unstable (see STAR 9001204800)
> +			 * We switched to the minimum possible value of the
> +			 * divisor (div-by-2) in HSDK platform code.
>   			 * So add temporary fix and change clock frequency
> -			 * from 100000000 to 12500000 Hz until we fix dw sdio
> -			 * driver itself.
> +			 * to 50000000 Hz until we fix dw sdio driver itself.
>   			 */
> -			clock-frequency = <12500000>;
> +			clock-frequency = <50000000>;
>   			#clock-cells = <0>;
>   		};
>   
> diff --git a/arch/arc/plat-hsdk/platform.c b/arch/arc/plat-hsdk/platform.c
> index 744e62e..5ea46b6 100644
> --- a/arch/arc/plat-hsdk/platform.c
> +++ b/arch/arc/plat-hsdk/platform.c
> @@ -74,6 +74,10 @@ static void __init hsdk_set_cpu_freq_1ghz(void)
>   		pr_err("Failed to setup CPU frequency to 1GHz!");
>   }
>   
> +#define SDIO_BASE		(ARC_PERIPHERAL_BASE + 0xA000)
> +#define SDIO_UHS_REG_EXT	(SDIO_BASE + 0x108)
> +#define SDIO_UHS_REG_EXT_DIV_2	(2 << 30)
> +
>   static void __init hsdk_init_early(void)
>   {
>   	/*
> @@ -89,6 +93,12 @@ static void __init hsdk_init_early(void)
>   	/* Really apply settings made above */
>   	writel(1, (void __iomem *) CREG_PAE_UPDATE);
>   
> +	/*

There was a white space damage here - I've fixed it locally.
I recommend following in ur .gitconfig

[apply]
     whitespace = fix

-Vineet

Re: [PATCH] ARC: [plat-hsdk]: Increase SDIO CIU frequency to 50000000Hz

[Alexey Brodkin]

Hi Eugeniy,

On Wed, 2017-10-11 at 20:01 +0300, Eugeniy Paltsev wrote:
> With current SDIO CIU clock frequency (12500000Hz) DW MMC
> controller fails to initialize some SD cards (which don't
> support slow mode).
> 
> So increase SDIO CIU frequency from 12500000Hz to 50000000Hz by
> switching from the default divisor value (div-by-8) to the
> minimum possible value of the divisor (div-by-2) in HSDK platform
> code.
> 
> Reported-by: Vineet Gupta <vgupta@synopsys.com>
> Tested-by: Vineet Gupta <vgupta@synopsys.com>
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>

Given this change doesn't introduce any regressions
or at least so far we only saw 1 card started to work
(confirmed by Vineet) while cards we tried locally continue to work...

Acked-by: Alexey Brodkin <abrodkin@synopsys.com>