Re: [PATCH v2 09/15] ARM: at91: pm: fix at91_suspend_finish for ZQ calibration

[Claudiu Beznea <claudiu.beznea@tuxon.dev>]

Hi, Ryan,

On 10.02.2025 23:13, Ryan.Wanner@microchip.com wrote:
> From: Li Bin <bin.li@microchip.com>
> 
> For sama7g5 and sama7d65 backup mode, we encountered a "ZQ calibrate error"
> during recalibrating the impedance in BootStrap.
> We found that the impedance value saved in at91_suspend_finish() before
> the DDR entered self-refresh mode did not match the resistor values. The
> ZDATA field in the DDR3PHY_ZQ0CR0 register uses a modified gray code to
> select the different impedance setting.
> But these gray code are incorrect, a workaournd from design team fixed the
> bug in the calibration logic. The ZDATA contains four independent impedance
> elements, but the algorithm combined the four elements into one. The elements
> were fixed using properly shifted offsets.
> 
> Signed-off-by: Li Bin <bin.li@microchip.com>
> [nicolas.ferre@microchip.com: fix indentation and combine 2 patches]
> Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
> Tested-by: Ryan Wanner <Ryan.Wanner@microchip.com>
> Tested-by: Durai Manickam KR <durai.manickamkr@microchip.com>
> Tested-by: Andrei Simion <andrei.simion@microchip.com>

Missing your SoB tag.

> ---
>  arch/arm/mach-at91/pm.c | 21 +++++++++++----------
>  1 file changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
> index 05a1547642b60..6c3e6aa22606f 100644
> --- a/arch/arm/mach-at91/pm.c
> +++ b/arch/arm/mach-at91/pm.c
> @@ -545,11 +545,12 @@ extern u32 at91_pm_suspend_in_sram_sz;
>  
>  static int at91_suspend_finish(unsigned long val)
>  {
> -	unsigned char modified_gray_code[] = {
> -		0x00, 0x01, 0x02, 0x03, 0x06, 0x07, 0x04, 0x05, 0x0c, 0x0d,
> -		0x0e, 0x0f, 0x0a, 0x0b, 0x08, 0x09, 0x18, 0x19, 0x1a, 0x1b,
> -		0x1e, 0x1f, 0x1c, 0x1d, 0x14, 0x15, 0x16, 0x17, 0x12, 0x13,
> -		0x10, 0x11,
> +	/* SYNOPSYS workaround to fix a bug in the calibration logic */
> +	unsigned char modified_fix_code[] = {
> +		0x00, 0x01, 0x01, 0x06, 0x07, 0x0c, 0x06, 0x07, 0x0b, 0x18,
> +		0x0a, 0x0b, 0x0c, 0x0d, 0x0d, 0x0a, 0x13, 0x13, 0x12, 0x13,
> +		0x14, 0x15, 0x15, 0x12, 0x18, 0x19, 0x19, 0x1e, 0x1f, 0x14,
> +		0x1e, 0x1f,
>  	};
>  	unsigned int tmp, index;
>  	int i;
> @@ -560,25 +561,25 @@ static int at91_suspend_finish(unsigned long val)
>  		 * restore the ZQ0SR0 with the value saved here. But the
>  		 * calibration is buggy and restoring some values from ZQ0SR0
>  		 * is forbidden and risky thus we need to provide processed
> -		 * values for these (modified gray code values).
> +		 * values for these.
>  		 */
>  		tmp = readl(soc_pm.data.ramc_phy + DDR3PHY_ZQ0SR0);
>  
>  		/* Store pull-down output impedance select. */
>  		index = (tmp >> DDR3PHY_ZQ0SR0_PDO_OFF) & 0x1f;
> -		soc_pm.bu->ddr_phy_calibration[0] = modified_gray_code[index];
> +		soc_pm.bu->ddr_phy_calibration[0] = modified_fix_code[index] << DDR3PHY_ZQ0SR0_PDO_OFF;
>  
>  		/* Store pull-up output impedance select. */
>  		index = (tmp >> DDR3PHY_ZQ0SR0_PUO_OFF) & 0x1f;
> -		soc_pm.bu->ddr_phy_calibration[0] |= modified_gray_code[index];
> +		soc_pm.bu->ddr_phy_calibration[0] |= modified_fix_code[index] << DDR3PHY_ZQ0SR0_PUO_OFF;
>  
>  		/* Store pull-down on-die termination impedance select. */
>  		index = (tmp >> DDR3PHY_ZQ0SR0_PDODT_OFF) & 0x1f;
> -		soc_pm.bu->ddr_phy_calibration[0] |= modified_gray_code[index];
> +		soc_pm.bu->ddr_phy_calibration[0] |= modified_fix_code[index] << DDR3PHY_ZQ0SR0_PDODT_OFF;
>  
>  		/* Store pull-up on-die termination impedance select. */
>  		index = (tmp >> DDR3PHY_ZQ0SRO_PUODT_OFF) & 0x1f;
> -		soc_pm.bu->ddr_phy_calibration[0] |= modified_gray_code[index];
> +		soc_pm.bu->ddr_phy_calibration[0] |= modified_fix_code[index] << DDR3PHY_ZQ0SRO_PUODT_OFF;
>  
>  		/*
>  		 * The 1st 8 words of memory might get corrupted in the process