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

[Alexey Brodkin]

Hi Vineet,

On Tue, 2017-10-10 at 10:09 -0700, Vineet Gupta wrote:
> On 10/10/2017 09:11 AM, Eugeniy Paltsev wrote:
> > 
> > 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.
> 
> Please describe the problem first not the solution. That some SD cards don't work 
> blah blah ....
> You could add me as reported-by - just for completeness !
> 
> While I will test it to see if it cures my issue, I'll need Alexey to sign off / 
> ack as well !

Sure once you update us with your findings and we know it helps you
(at least Bonnie++ stress-test with one of SD-cards here still works)
there will be a "normal" patch which I'll ack.

-Alexey

> 
> -Vineet
> 
> > 
> > 
> > Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev at synopsys.com>
> > ---
> > NOTE: This patch can possibly fix last issue with SD card initialization
> > fault.
> > 
> >   arch/arc/boot/dts/hsdk.dts    | 11 ++++++-----
> >   arch/arc/plat-hsdk/platform.c |  7 +++++++
> >   2 files changed, 13 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..f0cdb13 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 +93,9 @@ 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 div-by-8 to 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.
>