Re: [PATCH v2 3/4] watchdog: iTCO_wdt: Fix PMC GCR memory mapping failure

[sathyanarayanan kuppuswamy]

On 03/17/2017 06:40 AM, Guenter Roeck wrote:
> On 03/17/2017 04:43 AM, Rajneesh Bhardwaj wrote:
> > On Thu, Mar 16, 2017 at 05:41:35PM -0700, Kuppuswamy Sathyanarayanan 
> > wrote:
> > > Currently, iTCO watchdog driver uses memory map to access
> > > PMC_CFG GCR register. But the entire GCR address space is
> > > already mapped in intel_scu_ipc driver. So remapping the
> >
> > intel_pmc_ipc driver.
> >
> > > GCR register in this driver causes the mem request failure in
> > > iTCO_wdt probe function. This patch fixes this issue by
> > > using PMC GCR read/write API's to access PMC_CFG register.
> > >
> > > Signed-off-by: Kuppuswamy Sathyanarayanan 
> > > <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> > > ---
> > >  drivers/watchdog/iTCO_wdt.c | 31 +++++++------------------------
> > >  1 file changed, 7 insertions(+), 24 deletions(-)
> > >
> > > diff --git a/drivers/watchdog/iTCO_wdt.c b/drivers/watchdog/iTCO_wdt.c
> > > index 3d0abc0..31abfc5 100644
> > > --- a/drivers/watchdog/iTCO_wdt.c
> > > +++ b/drivers/watchdog/iTCO_wdt.c
> > > @@ -68,6 +68,8 @@
> > >  #include <linux/io.h>            /* For inb/outb/... */
> > >  #include <linux/platform_data/itco_wdt.h>
> > >
> > > +#include <asm/intel_pmc_ipc.h>
> > > +
> > >  #include "iTCO_vendor.h"
> > >
> > >  /* Address definitions for the TCO */
> > > @@ -94,12 +96,6 @@ struct iTCO_wdt_private {
> > >      unsigned int iTCO_version;
> > >      struct resource *tco_res;
> > >      struct resource *smi_res;
> > > -    /*
> > > -     * NO_REBOOT flag is Memory-Mapped GCS register bit 5 (TCO 
> > > version 2),
> > > -     * or memory-mapped PMC register bit 4 (TCO version 3).
> > > -     */
> >
> > Better to retain this comment elsewhere.
> >
> > > -    struct resource *gcs_pmc_res;
> > > -    unsigned long __iomem *gcs_pmc;
> > >      /* the lock for io operations */
> > >      spinlock_t io_lock;
> > >      /* the PCI-device */
> > > @@ -176,9 +172,9 @@ static void iTCO_wdt_set_NO_REBOOT_bit(struct 
> > > iTCO_wdt_private *p)
> > >
> > >      /* Set the NO_REBOOT bit: this disables reboots */
> > >      if (p->iTCO_version >= 2) {
> > > -        val32 = readl(p->gcs_pmc);
> > > +        val32 = intel_pmc_gcr_read(PMC_GCR_PMC_CFG_REG);
> >
> > better to have protection and error handling, discussed in v2, 2/4.
> >
> > compiled and tested this on APL and i see iTCO_WDT driver loads fine. 
> > Since
> > it impacts core WDT functionality, need to be thoroughly tested on 
> > various
> > platforms.
>
> I don't think I (or the watchdog mailing list) was copied on the 
> original patch.
Sorry. Its my mistake. I will fix it in next series update.
> Major immediate concern is that this introduces a dependency on 
> external code.
> The pmc_ipc driver's Kconfig entry states "This is not needed for PC-type
> machines". I don't know where the function is introduced, but I hope 
> this change
> does not require the pmc_ipc code to be present on such machines for 
> the watchdog
> to work. It would be bad if it does. If it doesn't, it appears that 
> the function
> should not be declared in asm/intel_pmc_ipc.h.
It should not create any compile time dependency with INTEL_PMC_IPC 
config option. If INTEL_PMC_IPC_CONFIG is disabled, we use
empty definitions for these calls defined in asm/intel_pmc_ipc.h

But iTCO_wdt driver already has runtime dependency with INTEL_PMIC_IPC 
if its version iTCO_version >= 2.

> Guenter

--
Sathyanarayanan Kuppuswamy
Android kernel developer