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

[Joacim Zetterling <joaze@westermo.com>]

On Fri, Oct 29, 2021 at 02:15:29PM +0200, Ahmad Fatoum wrote:
> Hi,
> 
> On 28.10.21 15:06, Joacim Zetterling wrote:
> > 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.
> 
> Now I wonder, how could v1 of this patch have worked for you?
> You should've had double the really existing RAM or am I missing something?
There was a mistake from my side when I prepared the patch where the
width was mistakely set back to 4. Before the width was set to 2, I got
as You say the double mem size and the memtest command failed.

All this is corrected in v2.
> 
> > 
> > 	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.
> >> -- 
> >> Pengutronix e.K.                           |                             |
> >> Steuerwalder Str. 21                       | https://urldefense.com/v3/__http://www.pengutronix.de/__;!!I9LPvj3b!UEEry3YzdrJRIMGgQgDd_crPHhM_0abIlHJq7-FIV6hTs9m7uhtHdAcHsA99yIw$   |
> >> 31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
> >> Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |
> > 
> 
> 
> -- 
> Pengutronix e.K.                           |                             |
> Steuerwalder Str. 21                       | https://urldefense.com/v3/__http://www.pengutronix.de/__;!!I9LPvj3b!TjpjVc01M7G9ikkRLRYrBUaGfra3FdKn89fwomU_lqiRKADVGxObbSWmFlqXHdE$   |
> 31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
> Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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