[PATCH 1/5] ahci: imx: Pull out the clock enable/disable calls
Marek Vasut
marex at denx.de
Wed Nov 20 04:55:53 EST 2013
Dear Eric Nelson,
> Hi Marek,
>
> On 11/18/2013 01:23 PM, Marek Vasut wrote:
> > Hi Eric,
> >
> >> Hi Marek,
> >>
> >> On 11/16/2013 06:20 PM, Marek Vasut wrote:
> >>> The same code for enabling and disabling SATA clock was found in
> >>> multiple places in the driver. Implement functions that enable/disable
> >>> the SATA clock and use them in such places instead of duplicating the
> >>> code.
> >>>
> >>> Signed-off-by: Marek Vasut <marex at denx.de>
> >>> Cc: Shawn Guo <shawn.guo at linaro.org>
> >>> Cc: Richard Zhu <r65037 at freescale.com>
> >>> Cc: Tejun Heo <tj at kernel.org>
> >>> Cc: Linux-IDE <linux-ide at vger.kernel.org>
> >>> ---
> >>>
> >>> drivers/ata/ahci_imx.c | 133
> >>> ++++++++++++++++++++++++++++--------------------- 1 file changed, 75
> >>> insertions(+), 58 deletions(-)
> >>>
> >>> diff --git a/drivers/ata/ahci_imx.c b/drivers/ata/ahci_imx.c
> >>> index ae2d73f..c7ee505 100644
> >>> --- a/drivers/ata/ahci_imx.c
> >>> +++ b/drivers/ata/ahci_imx.c
> >>> @@ -47,6 +47,73 @@ static int ahci_imx_hotplug;
> >>>
> >>> module_param_named(hotplug, ahci_imx_hotplug, int, 0644);
> >>> MODULE_PARM_DESC(hotplug, "AHCI IMX hot-plug support (0=Don't
> >>> support, 1=support)");
> >>>
> >>> <snip>
> >>
> >> I haven't traced through all of this, but if you're copying from
> >> the Freescale 3.0.35 kernel, note that there's a bug in it, and
> >> the 0x7FFFFFFD really wanted to be an 0x7FFFFFFF.
> >
> > I'm not taking this from FSL 3.0.35, no, but thanks for pointing this
> > out!
> >
> >> The way I read this comment, the writes need to happen in two
> >>
> >> steps:
> >> - write everything with the PHY disabled
> >> - enable the PHY
> >>
> >> We had reports of stalls waiting for SATA drives to be enumerated
> >> that were solved with this commit...
> >>
> >> https://github.com/boundarydevices/linux-
> >
> > imx6/commit/0186ea224ce6bd1cb4757
> >
> >> a0f83b0090e26a021f4
> >
> > [...]
> >
> >>> + regmap_update_bits(imxpriv->gpr, IOMUXC_GPR13,
> >>> + IMX6Q_GPR13_SATA_MPLL_CLK_EN,
> >>> + IMX6Q_GPR13_SATA_MPLL_CLK_EN);
> >
> > Isn't this snippet doing exactly what your patch does ?
>
> This part is doing the "set the bit" part:
> https://github.com/boundarydevices/linux-imx6/blob/boundary-
imx_3.0.35_4.1
> .0/arch/arm/mach-mx6/board-mx6_nitrogen6x.c#L728
>
> The previous block isn't clearing the enable bit though:
>
> + regmap_update_bits(imxpriv->gpr, IOMUXC_GPR13,
> + IMX6Q_GPR13_SATA_RX_EQ_VAL_MASK
> + | IMX6Q_GPR13_SATA_RX_LOS_LVL_MASK
> + | IMX6Q_GPR13_SATA_RX_DPLL_MODE_MASK
> + | IMX6Q_GPR13_SATA_SPD_MODE_MASK
> + | IMX6Q_GPR13_SATA_MPLL_SS_EN
> + | IMX6Q_GPR13_SATA_TX_ATTEN_MASK
> + | IMX6Q_GPR13_SATA_TX_BOOST_MASK
> + | IMX6Q_GPR13_SATA_TX_LVL_MASK
> + | IMX6Q_GPR13_SATA_TX_EDGE_RATE
> + , IMX6Q_GPR13_SATA_RX_EQ_VAL_3_0_DB
> + | IMX6Q_GPR13_SATA_RX_LOS_LVL_SATA2M
> + | IMX6Q_GPR13_SATA_RX_DPLL_MODE_2P_4F
> + | IMX6Q_GPR13_SATA_SPD_MODE_3P0G
> + | IMX6Q_GPR13_SATA_MPLL_SS_EN
> + | IMX6Q_GPR13_SATA_TX_ATTEN_9_16
> + | IMX6Q_GPR13_SATA_TX_BOOST_3_33_DB
> + | IMX6Q_GPR13_SATA_TX_LVL_1_025_V);
>
> The explicit clearing of bit 1 is what was necessary (and I think
> it's what the original author was after).
>
> This was a hard one to find, because it seems that it only shows
> up on some boards, and most of the time on those boards.
>
> Here are some references:
> http://boundarydevices.com/freescale-ubuntu-image-with-4-0-0-
kernel/#comme
> nt-60464
> http://boundarydevices.com/debian-installer-on-i-mx6-boards/#comment-76203
>
> The symptom is (was) that U-Boot worked 100% of the time, but
> the kernel failed to find the drive.
>
> Using 'mm' in U-Boot to clear the bit before kernel launch also
> allowed things to function.
Ah, now I see it. I will cook a patch, thanks!
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