[PATCH master 3/4] ddr: imx8m: workaround old spreadsheets not initializing ADDRMAP7

[Ahmad Fatoum]

Hi Teresa,

On 23.06.22 12:59, Teresa Remmet wrote:
> Hello Ahmad,
> 
> Am Donnerstag, dem 23.06.2022 um 12:30 +0200 schrieb Ahmad Fatoum:
>> Older NXP DDR spreadsheets don't initialize ADDRMAP7, leaving it at
>> its
>> POR default of zero. Now that barebox looks at ADDRMAP7 to be able to
>> correctly detect bigger memory sizes, barebox proper on out-of-tree
>> boards with older spreadsheets may read back 4x times as much RAM
>> as actually fitted.
>>
>> Work around this by writing a trailing 0xf0f (the neutral ignore-me
>> value for the register) if the register wasn't written through
>> dram_timing_info::ddrc_cfg. We consider this safe to do, because
>> the DDRC is held in reset while these values are programmed.
> 
> have you tried this patch without actually updating the RAM Timings (
> so patch 2/4)?

Yes. I've an out-of-tree i.MX8MM board with 1G of LPDDR4 and old RAM setup.

With upstream/next: 4G
With Workaround: 1G + Warning
With fixed ADDRMAP7: 1G, no warning

Reading back 0x3d40021c gives me 0xf0f as expected.

> I have just played around also setting ADDRMAP7 right before 
> ddr_cfg_umctl2() without fixing the timings and the register was 0
> again after startup and so the RAM size wrong.
> So it seems to me that the value is overwritten/resetted at some other
> point again ... or maybe I just did something wrong.

Strange. What SoC/board is this on?

Cheers,
Ahmad

> 
> Regards,
> Teresa
> 
>>
>> Fixes: dad2b5636bd8 ("ARM: imx: Add imx8 support for 18 bit SDRAM row
>> size handle")
>> Fixes: 6cf197fa61f9 ("arm: imx: mmdc_size: Increase row_max for
>> imx8m")
>> Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
>> ---
>>  drivers/ddr/imx8m/ddr_init.c | 18 ++++++++++++++++++
>>  drivers/ddr/imx8m/helper.c   |  6 ++++++
>>  include/soc/imx8m/ddr.h      |  1 +
>>  3 files changed, 25 insertions(+)
>>
>> diff --git a/drivers/ddr/imx8m/ddr_init.c
>> b/drivers/ddr/imx8m/ddr_init.c
>> index ae05b136229c..9a4b4e2ca88a 100644
>> --- a/drivers/ddr/imx8m/ddr_init.c
>> +++ b/drivers/ddr/imx8m/ddr_init.c
>> @@ -13,14 +13,32 @@
>>  #include <mach/imx8m-regs.h>
>>  #include <mach/imx8m-ccm-regs.h>
>>  
>> +bool imx8m_ddr_old_spreadsheet = true;
>> +
>>  static void ddr_cfg_umctl2(struct dram_cfg_param *ddrc_cfg, int num)
>>  {
>>  	int i = 0;
>>  
>>  	for (i = 0; i < num; i++) {
>> +		if (ddrc_cfg->reg == DDRC_ADDRMAP7(0))
>> +		    imx8m_ddr_old_spreadsheet = false;
>>  		reg32_write((unsigned long)ddrc_cfg->reg, ddrc_cfg-
>>> val);
>>  		ddrc_cfg++;
>>  	}
>> +
>> +	/*
>> +	 * Older NXP DDR configuration spreadsheets don't initialize
>> ADDRMAP7,
>> +	 * which falsifies the memory size read back from the
>> controller
>> +	 * in barebox proper.
>> +	 */
>> +	if (imx8m_ddr_old_spreadsheet) {
>> +		pr_warn("Working around old spreadsheet. Please
>> regenerate\n");
>> +		/*
>> +		 * Alternatively, stick { DDRC_ADDRMAP7(0), 0xf0f }
>> into
>> +		 * struct dram_timing_info::ddrc_cfg of your old timing
>> file
>> +		 */
>> +		reg32_write(DDRC_ADDRMAP7(0), 0xf0f);
>> +	}
>>  }
>>  
>>  /*
>> diff --git a/drivers/ddr/imx8m/helper.c b/drivers/ddr/imx8m/helper.c
>> index 94bbb811576d..98e40849584b 100644
>> --- a/drivers/ddr/imx8m/helper.c
>> +++ b/drivers/ddr/imx8m/helper.c
>> @@ -62,6 +62,12 @@ void dram_config_save(struct dram_timing_info
>> *timing_info,
>>  		cfg++;
>>  	}
>>  
>> +	if (imx8m_ddr_old_spreadsheet) {
>> +		cfg->reg = DDRC_ADDRMAP7(0);
>> +		cfg->val = 0xf0f;
>> +		cfg++;
>> +	}
>> +
>>  	/* save ddrphy config */
>>  	saved_timing->ddrphy_cfg = cfg;
>>  	for (i = 0; i < timing_info->ddrphy_cfg_num; i++) {
>> diff --git a/include/soc/imx8m/ddr.h b/include/soc/imx8m/ddr.h
>> index 9ae7cb877686..147a7d499aaf 100644
>> --- a/include/soc/imx8m/ddr.h
>> +++ b/include/soc/imx8m/ddr.h
>> @@ -407,6 +407,7 @@ static inline void reg32setbit(unsigned long
>> addr, u32 bit)
>>  #define dwc_ddrphy_apb_rd(addr) \
>>  	reg32_read(IOMEM(IP2APB_DDRPHY_IPS_BASE_ADDR(0)) + 4 * (addr))
>>  
>> +extern bool imx8m_ddr_old_spreadsheet;
>>  extern struct dram_cfg_param ddrphy_trained_csr[];
>>  extern uint32_t ddrphy_trained_csr_num;
>>  


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