linux-kernel - Re: [PATCH v4 1/3] mmc: dw_mmc: update clock after host reach a stable voltage

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Date:	Mon, 16 Feb 2015 04:58:47 +0530
From:	Alim Akhtar <alim.akhtar@...il.com>
To:	Addy Ke <addy.ke@...k-chips.com>
Cc:	Jaehoon Chung <jh80.chung@...sung.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Olof Johansson <olof@...om.net>,
	Andrzej Hajda <a.hajda@...sung.com>,
	Douglas Anderson <dianders@...omium.org>,
	Heiko Stübner <heiko@...ech.de>,
	Eddie Cai <cf@...k-chips.com>, lintao@...k-chips.com,
	Tao Huang <huangtao@...k-chips.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v4 1/3] mmc: dw_mmc: update clock after host reach a
 stable voltage

Hi Addy,

On Sat, Feb 14, 2015 at 11:47 AM, Addy Ke <addy.ke@...k-chips.com> wrote:
> As show in mmc_power_up(), in MMC_POWER_UP state, the voltage isn't
> stable and we may get 'data busy' which can't be cleaned by resetting
> all blocks. So we should not send command to update clock in this state.
>
> Signed-off-by: Addy Ke <addy.ke@...k-chips.com>
> ---
>  drivers/mmc/host/dw_mmc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 4d2e3c2..3472f9b 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -1102,7 +1102,8 @@ static void dw_mci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
>                 drv_data->set_ios(slot->host, ios);
>
>         /* Slot specific timing and width adjustment */
> -       dw_mci_setup_bus(slot, false);
> +       if (ios->power_mode != MMC_POWER_UP)
> +               dw_mci_setup_bus(slot, false);
>
This looks a HACK to me.
If stabilizing host voltage regulator is the problem, can you try out
below patch, and see if this resolve your issue?

===========
[PATCH] mmc: dw_mmc: Wait for host voltage regulator to be stable

Signed-off-by: Alim Akhtar <alim.akhtar@...sung.com>
---
 drivers/mmc/host/dw_mmc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 4d2e3c2..dc10fbb 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -1202,6 +1202,9 @@ static int dw_mci_switch_voltage(struct mmc_host
*mmc, struct mmc_ios *ios)
  }
  mci_writel(host, UHS_REG, uhs);

+ /* wait for 5ms so that host voltage regulator is stable */
+ usleep_range(5000, 5500);
+
  return 0;
 }

===============

>         if (slot->host->state == STATE_WAITING_CMD11_DONE && ios->clock != 0)
>                 slot->host->state = STATE_IDLE;
> --
> 1.8.3.2
>
>



-- 
Regards,
Alim
--
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