ARM: OMAP3: PM: correct enable/disable of daisy io chain

Currently the enabling and disabling of IO Daisy chain is not
according to the TRM. The below steps are followed to enable/
disable the IO chain, based loosely on the "Sec 3.5.7.2.2
I/O Wake-Up Mechanism" section in OMAP3630 Public TRM[1].

Steps to enable IO chain:
[a] Set PM_WKEN_WKUP.EN_IO bit
[b] Set the PM_WKEN_WKUP.EN_IO_CHAIN bit
[c] Poll for PM_WKST_WKUP.ST_IO_CHAIN.
[d] When ST_IO_CHAIN bit set to 1, clear PM_WKEN_WKUP.EN_IO_CHAIN
[e] Clear ST_IO_CHAIN bit.

Steps to disable IO chain:
[a] Clear PM_WKEN_WKUP.EN_IO_CHAIN bit
[b] Clear PM_WKEN_WKUP.EN_IO bit
[c] Clear PM_WKST_WKUP.ST_IO bit by writing 1 to it.

Step [e] & [c] in each case can be skipped, as these are handled
by the PRCM interrupt handler later.

[1] http://focus.ti.com/pdfs/wtbu/OMAP36xx_ES1.x_PUBLIC_TRM_vV.zip

Signed-off-by: Mohan V <mohanv@ti.com>
Signed-off-by: Vishwanath BS <vishwanath.bs@ti.com>
[paul@pwsan.com: modified commit message to clarify that these steps are
 based loosely on the TRM section, rather than documented exactly]
Reviewed-by: Rajendra Nayak <rnayak@ti.com>
[paul@pwsan.com: resolved new warnings from checkpatch]
Signed-off-by: Paul Walmsley <paul@pwsan.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/arch/arm/mach-omap2/pm34xx.c b/arch/arm/mach-omap2/pm34xx.c
index a34023d0ca7c..6d7f0d8a3103 100644
--- a/arch/arm/mach-omap2/pm34xx.c
+++ b/arch/arm/mach-omap2/pm34xx.c
@@ -81,16 +81,17 @@ static void omap3_enable_io_chain(void)
         /* Do a readback to assure write has been done */
         omap2_prm_read_mod_reg(WKUP_MOD, PM_WKEN);
 
-        while (!(omap2_prm_read_mod_reg(WKUP_MOD, PM_WKEN) &
+        while (!(omap2_prm_read_mod_reg(WKUP_MOD, PM_WKST) &
                  OMAP3430_ST_IO_CHAIN_MASK)) {
                 timeout++;
                 if (timeout > 1000) {
                         pr_err("Wake up daisy chain activation failed.\n");
                         return;
                 }
-                omap2_prm_set_mod_reg_bits(OMAP3430_ST_IO_CHAIN_MASK,
-                                           WKUP_MOD, PM_WKEN);
         }
+        omap2_prm_clear_mod_reg_bits(OMAP3430_EN_IO_CHAIN_MASK, WKUP_MOD,
+                                     PM_WKEN);
+
 }
 
 static void omap3_disable_io_chain(void)