Re: [PATCH] ARM: imx: Fix problem with imx_ddrc_sdram_size

[Joacim Zetterling <joaze@westermo.com>]

On Thu, Oct 28, 2021 at 02:19:18PM +0200, Ahmad Fatoum wrote:
> Hello Joacim,
> 
> On 28.10.21 10:46, Joacim Zetterling wrote:
> > The imx8mn has a 16-bit SDRAM bus width access but the calculation
> > of the memory size treat it as a 32-bit width bus which makes the
> > memory calculation to be wrong (meminfo wrong and memtest fails).
> 
> I missed this because of the /memory node in the device tree filling
> up the remainder. I removed /memory and tried your patch on an
> i.MX8MN DDR EVK, but it doesn't change iomem output:
> 
>   0x0000000040000000 - 0x000000007fffffff (size 0x0000000040000000) ram0
> 
> The 8MN DDR4 EVK reports FIELD_GET(DDRC_MSTR_DEVICE_CONFIG, mstr) == 0b10
> and FIELD_GET(DDRC_MSTR_DATA_BUS_WIDTH, mstr) == 0b00.
> 
> > There is a difference between the imx7 and the imx8 familys.
> > The imx8 family has a device config field in the master register of
> > the DDRC controller which the imx7 family doesn't have (the bus width
> > is 32-bit as default).
> > 
> > The device config field together with the DQ configuration tells us
> > the actual bus width of the device for a correct mem size calculaton.
> > 
> > From the imx8mn reference manual:
> > +----------------------------------------------------+
> > |    Field      |     Function                       |
> > |----------------------------------------------------|
> > |    31-30      | Indicates the configuration of the |
> > |               | device used in the system.         |
> > | device_config |     00b - x4 device                |
> > |               |     01b - x8 device                |
> > |               |     10b - x16 device               |
> > |               |     11b - x32 device               |
> > +----------------------------------------------------+
> > ...
> > ...
> > 
> > Tested on the IMX8MN Evk with 2GB DDR4 and on a IMX8MN custom board
> > with 2GB LPDDR4, checked size and made memory test.
> 
> What's the device_config for each?
The device_config for both platforms are b10

> 
> > Signed-off-by: Joacim Zetterling <joacim.zetterling@westermo.com>
> > ---
> >  arch/arm/mach-imx/esdctl.c | 16 +++++++++++-----
> >  1 file changed, 11 insertions(+), 5 deletions(-)
> > 
> > diff --git a/arch/arm/mach-imx/esdctl.c b/arch/arm/mach-imx/esdctl.c
> > index e56da3cb76d4..f80d94f2fca0 100644
> > --- a/arch/arm/mach-imx/esdctl.c
> > +++ b/arch/arm/mach-imx/esdctl.c
> > @@ -320,6 +320,7 @@ static int vf610_ddrmc_add_mem(void *mmdcbase, struct imx_esdctl_data *data)
> >  #define DDRC_MSTR_LPDDR4			BIT(5)
> >  #define DDRC_MSTR_DATA_BUS_WIDTH		GENMASK(13, 12)
> >  #define DDRC_MSTR_ACTIVE_RANKS			GENMASK(27, 24)
> > +#define DDRC_MSTR_DEVICE_CONFIG		GENMASK(31, 30)
> >  
> >  #define DDRC_ADDRMAP0_CS_BIT1			GENMASK(12,  8)
> >  
> > @@ -361,7 +362,7 @@ static resource_size_t
> >  imx_ddrc_sdram_size(void __iomem *ddrc, const u32 addrmap[],
> >  		    u8 col_max, const u8 col_b[], unsigned int col_b_num,
> >  		    u8 row_max, const u8 row_b[], unsigned int row_b_num,
> > -		    bool reduced_adress_space)
> > +		    bool reduced_adress_space, bool is_imx8)
> >  {
> >  	const u32 mstr = readl(ddrc + DDRC_MSTR);
> >  	unsigned int banks, ranks, columns, rows, active_ranks, width;
> > @@ -384,15 +385,20 @@ imx_ddrc_sdram_size(void __iomem *ddrc, const u32 addrmap[],
> >  		BUG();
> >  	}
> >  
> > +	if (is_imx8)
> > +		width = (1 << FIELD_GET(DDRC_MSTR_DEVICE_CONFIG, mstr)) >> 1;
> 
> for device_config == 0, size should be halved, but instead you would get a
> width of zero here.
Good catch! Need to treat bus width 4 in a special way when calculating
the memory size. i.e.

	if (width)
		size = memory_sdram_size(columns, rows, 1 << banks, width);
	else
		size = memory_sdram_size(columns, rows, 1 << banks, 1) >> 1;
	size <<= ranks;

> 
> > +	else
> > +		width = 4;
> > +
> >  	switch (FIELD_GET(DDRC_MSTR_DATA_BUS_WIDTH, mstr)) {
> >  	case 0b00:	/* Full DQ bus  */
> >  		width = 4;
> 
> I can't really follow. Shouldn't this be dropped to take the
> value of width above?
My bad! Should have been removed earlier.

	switch (FIELD_GET(DDRC_MSTR_DATA_BUS_WIDTH, mstr)) {
	case 0b00:	/* Full DQ bus  */
		break;
	case 0b01:	/* Half DQ bus  */
        ...
	...
> 
> >  		break;
> >  	case 0b01:      /* Half DQ bus  */
> > -		width = 2;
> > +		width >>= 1;
> >  		break;
> >  	case 0b10:	/* Quarter DQ bus  */
> > -		width = 1;
> > +		width >>= 2;
> >  		break;
> >  	default:
> >  		BUG();
> > @@ -466,7 +472,7 @@ static resource_size_t imx8m_ddrc_sdram_size(void __iomem *ddrc)
> >  	return imx_ddrc_sdram_size(ddrc, addrmap,
> >  				   12, ARRAY_AND_SIZE(col_b),
> >  				   16, ARRAY_AND_SIZE(row_b),
> > -				   reduced_adress_space);
> > +				   reduced_adress_space, true);
> >  }
> >  
> >  static int imx8m_ddrc_add_mem(void *mmdcbase, struct imx_esdctl_data *data)
> > @@ -508,7 +514,7 @@ static resource_size_t imx7d_ddrc_sdram_size(void __iomem *ddrc)
> >  	return imx_ddrc_sdram_size(ddrc, addrmap,
> >  				   11, ARRAY_AND_SIZE(col_b),
> >  				   15, ARRAY_AND_SIZE(row_b),
> > -				   reduced_adress_space);
> > +				   reduced_adress_space, false);
> >  }
> >  
> >  static int imx7d_ddrc_add_mem(void *mmdcbase, struct imx_esdctl_data *data)
> > 
> 
> 
I'll send a new patch version.
> -- 
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