| Message ID | 20190926191755.27131-2-digetx@gmail.com |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [v5,1/2] soc/tegra: pmc: Query PCLK clock rate at probe time | expand |
On Thu, Sep 26, 2019 at 10:17:55PM +0300, Dmitry Osipenko wrote: > The removed barrier isn't needed because writes/reads are strictly ordered > and even if PMC had separate ports for writes, it wouldn't matter since > the hardware logic takes into effect after triggering CPU's power-gating > and at that point all CPU accesses are guaranteed to be completed. That > barrier was copied from the old arch/ code during transition to the soc/ > PMC driver and even that the code structure was different back then, the > barrier didn't have a real useful purpose from the start. Lastly, the > tegra_pmc_writel() naturally inserts wmb() because it uses writel(), > and thus this change doesn't actually make any difference in terms of > interacting with hardware. Hence let's remove the barrier to clean up > code a tad. > > Signed-off-by: Dmitry Osipenko <digetx@gmail.com> > --- > > Changelog: > > v5: Extended the commit's message. > > v4: No changes. > > v3: No changes. > > v2: New patch that was added after Jon's Hunter pointing that it's better > not to change the barrier's placement in the code. In fact the barrier > is not needed at all. > > drivers/soc/tegra/pmc.c | 2 -- > 1 file changed, 2 deletions(-) Applied to for-5.5/soc, thanks. Thierry
diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c index ee39ded6bc7b..f75708a935ac 100644 --- a/drivers/soc/tegra/pmc.c +++ b/drivers/soc/tegra/pmc.c @@ -1463,8 +1463,6 @@ void tegra_pmc_enter_suspend_mode(enum tegra_suspend_mode mode) do_div(ticks, USEC_PER_SEC); tegra_pmc_writel(pmc, ticks, PMC_CPUPWROFF_TIMER); - wmb(); - value = tegra_pmc_readl(pmc, PMC_CNTRL); value &= ~PMC_CNTRL_SIDE_EFFECT_LP0; value |= PMC_CNTRL_CPU_PWRREQ_OE;
The removed barrier isn't needed because writes/reads are strictly ordered and even if PMC had separate ports for writes, it wouldn't matter since the hardware logic takes into effect after triggering CPU's power-gating and at that point all CPU accesses are guaranteed to be completed. That barrier was copied from the old arch/ code during transition to the soc/ PMC driver and even that the code structure was different back then, the barrier didn't have a real useful purpose from the start. Lastly, the tegra_pmc_writel() naturally inserts wmb() because it uses writel(), and thus this change doesn't actually make any difference in terms of interacting with hardware. Hence let's remove the barrier to clean up code a tad. Signed-off-by: Dmitry Osipenko <digetx@gmail.com> --- Changelog: v5: Extended the commit's message. v4: No changes. v3: No changes. v2: New patch that was added after Jon's Hunter pointing that it's better not to change the barrier's placement in the code. In fact the barrier is not needed at all. drivers/soc/tegra/pmc.c | 2 -- 1 file changed, 2 deletions(-)