[PATCH] ahci: imx: manage only sata_ref_clk in imx_sata_enable[disable]

[Tejun Heo]

On Wed, May 28, 2014 at 11:05:39PM +0800, Shawn Guo wrote:
> Doing suspend/resume on imx6q and imx53 boards with no SATA disk
> attached will trigger the following warning.
> 
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 661 at drivers/ata/libahci.c:224 ahci_enable_ahci+0x74/0x8)
> Modules linked in:
> CPU: 0 PID: 661 Comm: sh Tainted: G        W     3.15.0-rc5-next-20140521-000027
> Backtrace:
> [<80011c90>] (dump_backtrace) from [<80011e2c>] (show_stack+0x18/0x1c)
>  r6:803a22f4 r5:00000000 r4:00000000 r3:00000000
> [<80011e14>] (show_stack) from [<80661e60>] (dump_stack+0x88/0xa4)
> [<80661dd8>] (dump_stack) from [<80028fdc>] (warn_slowpath_common+0x70/0x94)
>  r5:00000009 r4:00000000
> [<80028f6c>] (warn_slowpath_common) from [<80029024>] (warn_slowpath_null+0x24/)
>  r8:808f68c4 r7:00000000 r6:00000000 r5:00000000 r4:e0810004
> [<80029000>] (warn_slowpath_null) from [<803a22f4>] (ahci_enable_ahci+0x74/0x80)
> [<803a2280>] (ahci_enable_ahci) from [<803a2324>] (ahci_reset_controller+0x24/0)
>  r8:ddcd9410 r7:80351178 r6:ddcd9444 r5:dde8b850 r4:e0810000 r3:ddf35e90
> [<803a2300>] (ahci_reset_controller) from [<803a2c68>] (ahci_platform_resume_ho)
>  r7:80351178 r6:ddcd9444 r5:dde8b850 r4:ddcd9410
> [<803a2c30>] (ahci_platform_resume_host) from [<803a38f0>] (imx_ahci_resume+0x2)
>  r5:00000000 r4:ddcd9410
> [<803a38c4>] (imx_ahci_resume) from [<803511ac>] (platform_pm_resume+0x34/0x54)
> ....
> 
> The reason is that the SATA controller has no working clock at this
> point, and thus ahci_enable_ahci() fails to enable the controller.  In
> case that there is no SATA disk attached, the imx_sata_disable() gets
> called in ahci_imx_error_handler(), and both sata_clk and sata_ref_clk
> will be disabled there.  Because all the imx_sata_enable() calls
> afterward will return immediately due to imxpriv->no_device check, the
> SATA controller working clock sata_clk will never get any chance to be
> enabled again.
> 
> This is a regression caused by commit 90870d79d4f2 (ahci-imx: Port to
> library-ised ahci_platform).  Before the commit, only sata_ref_clk is
> managed by the driver in enable/disable function.  But after the commit,
> all the clocks are enabled/disabled in a row by ahci platform helpers
> ahci_platform_enable[disable]_clks.  Since ahb_clk is a bus clock which
> does not have gate at all, and i.MX low-power hardware module already
> manages sata_clk across suspend/resume cycle, the only clock that needs
> to be managed by software is sata_ref_clk.
> 
> So instead of using ahci_platform_enable[disable]_clks to manage all
> the clocks in a row from imx_sata_enable[disable], we should manage
> only sata_ref_clk in there.
> 
> Reported-by: Fabio Estevam <fabio.estevam at freescale.com>
> Fixes: 90870d79d4f2 (ahci-imx: Port to library-ised ahci_platform)
> Signed-off-by: Shawn Guo <shawn.guo at freescale.com>

Applied to libata/for-3.16-fixes.

Thanks.

-- 
tejun