Re: [PATCH 2/2] mmc: fsl_esdhc: make sure delay chain locked for HS400

20 Oct 2020

On 10/20/20 12:20 PM, Y.b. Lu wrote:
...
Hi Jaehoon,
...
-----Original Message-----
From: Jaehoon Chung jh80.chung@samsung.com
Sent: Tuesday, October 20, 2020 5:52 AM
To: Y.b. Lu yangbo.lu@nxp.com; u-boot@lists.denx.de; Peng Fan
peng.fan@nxp.com
Subject: Re: [PATCH 2/2] mmc: fsl_esdhc: make sure delay chain locked for
HS400
Dear Yangbo,
On 10/16/20 12:13 PM, Yangbo Lu wrote:
...
For eMMC HS400 mode, the DLL reset is a required step for mmc rescan.
This step has not been documented in reference manual, but the RM will
be fixed sooner or later.
This patch is to add the step of DLL reset, and make sure delay chain
locked for HS400.
Fixes: db8f93672b42 ("mmc: fsl_esdhc: support eMMC HS400 mode")
Signed-off-by: Yangbo Lu yangbo.lu@nxp.com
Reviewed-by: Jaehoon Chung jh80.chung@samsung.com
Just added minor comments.
...

drivers/mmc/fsl_esdhc.c | 28 +++++++++++++++++++++++++---
 include/fsl_esdhc.h     |  4 ++++
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/drivers/mmc/fsl_esdhc.c b/drivers/mmc/fsl_esdhc.c
index 68130ee..a18316e 100644
--- a/drivers/mmc/fsl_esdhc.c
+++ b/drivers/mmc/fsl_esdhc.c
@@ -70,7 +70,9 @@ struct fsl_esdhc {
   uint	sdtimingctl;	/* SD timing control register */
   char    reserved8[20];	/* reserved */
   uint	dllcfg0;	/* DLL config 0 register */

char    reserved9[680];	/* reserved */


char	reserved9[12];	/* reserved */
uint	dllstat0;	/* DLL status 0 register */
char    reserved10[664];/* reserved */
uint    esdhcctl;	/* eSDHC control register */

};
@@ -617,9 +619,11 @@ static void esdhc_exit_hs400(struct fsl_esdhc_priv
*priv)
...
esdhc_tuning_block_enable(priv, false);
 }
-static void esdhc_set_timing(struct fsl_esdhc_priv *priv, enum bus_mode
mode)
...
+static int esdhc_set_timing(struct fsl_esdhc_priv *priv, enum bus_mode
mode)
...
{
   struct fsl_esdhc *regs = priv->esdhc_regs;

ulong start;

u32 val;
/* Exit HS400 mode before setting any other mode */
if (esdhc_read32(&regs->tbctl) & HS400_MODE &&


@@ -640,17 +644,33 @@ static void esdhc_set_timing(struct fsl_esdhc_priv
*priv, enum bus_mode mode)
...
	esdhc_setbits32(&regs->dllcfg0, DLL_FREQ_SEL);

esdhc_setbits32(&regs->dllcfg0, DLL_ENABLE);



esdhc_setbits32(&regs->dllcfg0, DLL_RESET);


udelay(1);



Could you add a light comment why need to put udelay(1)?
Actually this is just per fixed reference manual.
I sent out v2 patch, to explain in commit message in case some one what to know why.
"    In previous commit to support eMMC HS400,
      db8f936 mmc: fsl_esdhc: support eMMC HS400 mode
the steps to configure DLL could be found in commit message,
  13. Set DLLCFG0[DLL_ENABLE] and DLLCFG0[DLL_FREQ_SEL].
  14. Wait for delay chain to lock.

these would be fixed as,
  13.   Set DLLCFG0[DLL_ENABLE] and DLLCFG0[DLL_FREQ_SEL].
  13.1  Write DLLCFG0[DLL_RESET] to 1 and wait for 1us,
        then write DLLCFG0[DLL_RESET]
  14.   Wait for delay chain to lock."


Thanks.
Thanks you for kindly explanation.
Best Regards,
Jaehoon Chung
...
...
Best Regards,
Jaehoon Chung
...

esdhc_clrbits32(&regs->dllcfg0, DLL_RESET);



start = get_timer(0);


val = DLL_STS_SLV_LOCK;


while (!(esdhc_read32(&regs->dllstat0) & val)) {


	if (get_timer(start) > 1000) {


		printf("fsl_esdhc: delay chain lock timeout\n");


		return -ETIMEDOUT;


	}


}


esdhc_setbits32(&regs->tbctl, HS400_WNDW_ADJUST);
esdhc_clock_control(priv, false);
  esdhc_flush_async_fifo(priv);
 }
 esdhc_clock_control(priv, true);

return 0;


}
static int esdhc_set_ios_common(struct fsl_esdhc_priv *priv, struct mmc
*mmc)
...
{
   struct fsl_esdhc *regs = priv->esdhc_regs;

int ret;
if (priv->is_sdhc_per_clk) {
/* Select to use peripheral clock */


@@ -667,7 +687,9 @@ static int esdhc_set_ios_common(struct
fsl_esdhc_priv *priv, struct mmc *mmc)
...
set_sysctl(priv, mmc, mmc->clock);


/* Set timing */

esdhc_set_timing(priv, mmc->selected_mode);


ret = esdhc_set_timing(priv, mmc->selected_mode);

if (ret)

return ret;


/* Set the bus width */
esdhc_clrbits32(&regs->proctl, PROCTL_DTW_4 | PROCTL_DTW_8);


diff --git a/include/fsl_esdhc.h b/include/fsl_esdhc.h
index e6f1c75..850a304 100644
--- a/include/fsl_esdhc.h
+++ b/include/fsl_esdhc.h
@@ -187,8 +187,12 @@
/* DLL config 0 register */
 #define DLL_ENABLE		0x80000000
+#define DLL_RESET		0x40000000
 #define DLL_FREQ_SEL		0x08000000
+/* DLL status 0 register */
+#define DLL_STS_SLV_LOCK	0x08000000



#define MAX_TUNING_LOOP		40
#define HOSTVER_VENDOR(x)	(((x) >> 8) & 0xff)

    