[PATCH] ddr: imx8m: add comment and print out prior to first DDRC read

[PATCH] ddr: imx8m: add comment and print out prior to first DDRC read

[Ahmad Fatoum]

If board code low level entry forgets to call imx8m*_early_clock_init
before DRAM setup, write access to DRAM controller will seem to work,
but the first read access will hang the system.

Make debugging this board bring up mistake easier by adding a debug
print along with a comment.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 drivers/ddr/imx8m/ddr_init.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/ddr/imx8m/ddr_init.c b/drivers/ddr/imx8m/ddr_init.c
index 944cc3873e0c..9a86280d9c73 100644
--- a/drivers/ddr/imx8m/ddr_init.c
+++ b/drivers/ddr/imx8m/ddr_init.c
@@ -106,7 +106,11 @@ int imx8m_ddr_init(struct dram_timing_info *dram_timing,
 	reg32_write(DDRC_RFSHCTL3(0), 0x0000001);
 	reg32_write(DDRC_PWRCTL(0), 0xa0);
 
-	/* if ddr type is LPDDR4, do it */
+	pr_debug("checking ddr type\n");
+	/*
+	 * below is first read, so if boot hangs here, imx8m*_early_clock_init()
+	 * might not have been called
+	 */
 	tmp = reg32_read(DDRC_MSTR(0));
 	if (tmp & (0x1 << 5) && ddrc_type != DDRC_TYPE_MN)
 		reg32_write(DDRC_DDR_SS_GPR0, 0x01); /* LPDDR4 mode */
-- 
2.39.2

Re: [PATCH] ddr: imx8m: add comment and print out prior to first DDRC read

[Marco Felsch]

On 23-07-06, Ahmad Fatoum wrote:
> If board code low level entry forgets to call imx8m*_early_clock_init
> before DRAM setup, write access to DRAM controller will seem to work,
> but the first read access will hang the system.
> 
> Make debugging this board bring up mistake easier by adding a debug
> print along with a comment.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>

Reviewed-by: Marco Felsch <m.felsch@pengutronix.de>

> ---
>  drivers/ddr/imx8m/ddr_init.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/ddr/imx8m/ddr_init.c b/drivers/ddr/imx8m/ddr_init.c
> index 944cc3873e0c..9a86280d9c73 100644
> --- a/drivers/ddr/imx8m/ddr_init.c
> +++ b/drivers/ddr/imx8m/ddr_init.c
> @@ -106,7 +106,11 @@ int imx8m_ddr_init(struct dram_timing_info *dram_timing,
>  	reg32_write(DDRC_RFSHCTL3(0), 0x0000001);
>  	reg32_write(DDRC_PWRCTL(0), 0xa0);
>  
> -	/* if ddr type is LPDDR4, do it */
> +	pr_debug("checking ddr type\n");
> +	/*
> +	 * below is first read, so if boot hangs here, imx8m*_early_clock_init()
> +	 * might not have been called
> +	 */
>  	tmp = reg32_read(DDRC_MSTR(0));
>  	if (tmp & (0x1 << 5) && ddrc_type != DDRC_TYPE_MN)
>  		reg32_write(DDRC_DDR_SS_GPR0, 0x01); /* LPDDR4 mode */
> -- 
> 2.39.2
> 
> 
> 

Re: [PATCH] ddr: imx8m: add comment and print out prior to first DDRC read

[Sascha Hauer]

On Thu, Jul 06, 2023 at 06:16:40PM +0200, Ahmad Fatoum wrote:
> If board code low level entry forgets to call imx8m*_early_clock_init
> before DRAM setup, write access to DRAM controller will seem to work,
> but the first read access will hang the system.
> 
> Make debugging this board bring up mistake easier by adding a debug
> print along with a comment.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  drivers/ddr/imx8m/ddr_init.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)

Applied, thanks

Sascha

> 
> diff --git a/drivers/ddr/imx8m/ddr_init.c b/drivers/ddr/imx8m/ddr_init.c
> index 944cc3873e0c..9a86280d9c73 100644
> --- a/drivers/ddr/imx8m/ddr_init.c
> +++ b/drivers/ddr/imx8m/ddr_init.c
> @@ -106,7 +106,11 @@ int imx8m_ddr_init(struct dram_timing_info *dram_timing,
>  	reg32_write(DDRC_RFSHCTL3(0), 0x0000001);
>  	reg32_write(DDRC_PWRCTL(0), 0xa0);
>  
> -	/* if ddr type is LPDDR4, do it */
> +	pr_debug("checking ddr type\n");
> +	/*
> +	 * below is first read, so if boot hangs here, imx8m*_early_clock_init()
> +	 * might not have been called
> +	 */
>  	tmp = reg32_read(DDRC_MSTR(0));
>  	if (tmp & (0x1 << 5) && ddrc_type != DDRC_TYPE_MN)
>  		reg32_write(DDRC_DDR_SS_GPR0, 0x01); /* LPDDR4 mode */
> -- 
> 2.39.2
> 
> 
> 

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