Subject: Re: [PATCH net-next v2] net: ethernet: ti: am65-cpsw/cpts: Fix CPTS release action

From: Leon Romanovsky <[email-masked]>
Date: Mon, 16 Jan 2023 12:04:33 +0200

On Mon, Jan 16, 2023 at 01:13:36PM +0530, Siddharth Vadapalli wrote:
> 
> 
> On 16/01/23 13:00, Leon Romanovsky wrote:
> > On Mon, Jan 16, 2023 at 10:15:17AM +0530, Siddharth Vadapalli wrote:
> >> The am65_cpts_release() function is registered as a devm_action in the
> >> am65_cpts_create() function in am65-cpts driver. When the am65-cpsw driver
> >> invokes am65_cpts_create(), am65_cpts_release() is added in the set of devm
> >> actions associated with the am65-cpsw driver's device.
> >>
> >> In the event of probe failure or probe deferral, the platform_drv_probe()
> >> function invokes dev_pm_domain_detach() which powers off the CPSW and the
> >> CPSW's CPTS hardware, both of which share the same power domain. Since the
> >> am65_cpts_disable() function invoked by the am65_cpts_release() function
> >> attempts to reset the CPTS hardware by writing to its registers, the CPTS
> >> hardware is assumed to be powered on at this point. However, the hardware
> >> is powered off before the devm actions are executed.
> >>
> >> Fix this by getting rid of the devm action for am65_cpts_release() and
> >> invoking it directly on the cleanup and exit paths.
> >>
> >> Fixes: f6bd59526ca5 ("net: ethernet: ti: introduce am654 common platform time sync driver")
> >> Signed-off-by: Siddharth Vadapalli <[email-masked]>
> >> Reviewed-by: Roger Quadros <[email-masked]>
> >> ---
> >> Changes from v1:
> >> 1. Fix the build issue when "CONFIG_TI_K3_AM65_CPTS" is not set. This
> >>    error was reported by kernel test robot <[email-masked]> at:
> >>    https://lore.kernel.org/r/[email-masked]/
> >> 2. Collect Reviewed-by tag from Roger Quadros.
> >>
> >> v1:
> >> https://lore.kernel.org/r/[email-masked]/
> >>
> >>  drivers/net/ethernet/ti/am65-cpsw-nuss.c |  8 ++++++++
> >>  drivers/net/ethernet/ti/am65-cpts.c      | 15 +++++----------
> >>  drivers/net/ethernet/ti/am65-cpts.h      |  5 +++++
> >>  3 files changed, 18 insertions(+), 10 deletions(-)
> >>
> >> diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> >> index 5cac98284184..00f25d8a026b 100644
> >> --- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> >> +++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> >> @@ -1913,6 +1913,12 @@ static int am65_cpsw_am654_get_efuse_macid(struct device_node *of_node,
> >>  	return 0;
> >>  }
> >>  
> >> +static void am65_cpsw_cpts_cleanup(struct am65_cpsw_common *common)
> >> +{
> >> +	if (IS_ENABLED(CONFIG_TI_K3_AM65_CPTS) && common->cpts)
> > 
> > Why do you have IS_ENABLED(CONFIG_TI_K3_AM65_CPTS), if
> > am65_cpts_release() defined as empty when CONFIG_TI_K3_AM65_CPTS not set?
> > 
> > How is it possible to have common->cpts == NULL?
> 
> Thank you for reviewing the patch. I realize now that checking
> CONFIG_TI_K3_AM65_CPTS is unnecessary.
> 
> common->cpts remains NULL in the following cases:
> 1. am65_cpsw_init_cpts() returns 0 since CONFIG_TI_K3_AM65_CPTS is not enabled.

In this case am65_cpsw_cpts_cleanup() will NOP as well.

> 2. am65_cpsw_init_cpts() returns -ENOENT since the cpts node is not defined.

It is an error and all callers unwind properly.

> 3. The call to am65_cpts_create() fails within the am65_cpsw_init_cpts()
> function with a return value of 0 when cpts is disabled.

It is disabled by CONFIG_TI_K3_AM65_CPTS, which in turn will make
am65_cpsw_cpts_cleanup() NOP.

> 4. The call to am65_cpts_create() within the am65_cpsw_init_cpts() function
> fails with an error.
> 
> Of the above cases, the am65_cpsw_cpts_cleanup() function would have to handle
> cases 1 and 3, since the probe might fail at a later point, following which the
> probe cleanup path will invoke the am65_cpts_cpts_cleanup() function. This
> function then checks for common->cpts not being NULL, so that it can invoke the
> am65_cpts_release() function with this pointer.

I still don't see how it is possible.

Thanks