| Message ID | 20190723025245.27754-1-digetx@gmail.com |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | [v2,1/2] clk: tegra: divider: Add missing check for enable-bit on rate's recalculation | expand |
23.07.2019 5:52, Dmitry Osipenko пишет: > Unset "enable" bit means that divider is in bypass mode, hence it doesn't > have any effect in that case. Please note that there are no known bugs > caused by the missing check. > > Signed-off-by: Dmitry Osipenko <digetx@gmail.com> > --- > > Changelog: > > v2: Changed the commit's description from 'Fix' to 'Add' in response to the > Stephen's Boyd question about the need to backport the patch into stable > kernels. The backporting is not really needed. > > drivers/clk/tegra/clk-divider.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/drivers/clk/tegra/clk-divider.c b/drivers/clk/tegra/clk-divider.c > index e76731fb7d69..f33c19045386 100644 > --- a/drivers/clk/tegra/clk-divider.c > +++ b/drivers/clk/tegra/clk-divider.c > @@ -40,8 +40,13 @@ static unsigned long clk_frac_div_recalc_rate(struct clk_hw *hw, > int div, mul; > u64 rate = parent_rate; > > - reg = readl_relaxed(divider->reg) >> divider->shift; > - div = reg & div_mask(divider); > + reg = readl_relaxed(divider->reg); > + > + if ((divider->flags & TEGRA_DIVIDER_UART) && > + !(reg & PERIPH_CLK_UART_DIV_ENB)) > + return rate; > + > + div = (reg >> divider->shift) & div_mask(divider); > > mul = get_mul(divider); > div += mul; > Hello Peter, ACK?
On Tue, Jul 23, 2019 at 05:52:44AM +0300, Dmitry Osipenko wrote: > Unset "enable" bit means that divider is in bypass mode, hence it doesn't > have any effect in that case. Please note that there are no known bugs > caused by the missing check. > Technically this is not quite true, but for the purposes of CCF you can treat it that way. This bits defines if the value in the lower 16 bits of the divider register is used to configure the divider or if the contents of the UART DLM/DLL registers is used. So the divider isn't actually bypassed, it's just configured differently. In practice this bit is only set when the divider is non-zero when doing set rate. So the extra test isn't strictly needed as long as the sw running before the kernel also ensures the bit is only set when the divider is non-zero. Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com> > Signed-off-by: Dmitry Osipenko <digetx@gmail.com> > --- > > Changelog: > > v2: Changed the commit's description from 'Fix' to 'Add' in response to the > Stephen's Boyd question about the need to backport the patch into stable > kernels. The backporting is not really needed. > > drivers/clk/tegra/clk-divider.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/drivers/clk/tegra/clk-divider.c b/drivers/clk/tegra/clk-divider.c > index e76731fb7d69..f33c19045386 100644 > --- a/drivers/clk/tegra/clk-divider.c > +++ b/drivers/clk/tegra/clk-divider.c > @@ -40,8 +40,13 @@ static unsigned long clk_frac_div_recalc_rate(struct clk_hw *hw, > int div, mul; > u64 rate = parent_rate; > > - reg = readl_relaxed(divider->reg) >> divider->shift; > - div = reg & div_mask(divider); > + reg = readl_relaxed(divider->reg); > + > + if ((divider->flags & TEGRA_DIVIDER_UART) && > + !(reg & PERIPH_CLK_UART_DIV_ENB)) > + return rate; > + > + div = (reg >> divider->shift) & div_mask(divider); > > mul = get_mul(divider); > div += mul; > -- > 2.22.0 >
28.10.2019 17:27, Peter De Schrijver пишет: > On Tue, Jul 23, 2019 at 05:52:44AM +0300, Dmitry Osipenko wrote: >> Unset "enable" bit means that divider is in bypass mode, hence it doesn't >> have any effect in that case. Please note that there are no known bugs >> caused by the missing check. >> > > Technically this is not quite true, but for the purposes of CCF you can > treat it that way. This bits defines if the value in the lower 16 bits > of the divider register is used to configure the divider or if the > contents of the UART DLM/DLL registers is used. So the divider isn't > actually bypassed, it's just configured differently. > In practice this bit is only set when the divider is non-zero when doing > set rate. So the extra test isn't strictly needed as long as the sw > running before the kernel also ensures the bit is only set when the > divider is non-zero. > > Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com> Thank you for the clarification. I hope that bootloader doesn't enable the divider because it looks like standard 8250 driver won't be ready for that. But serial-tegra driver seems should be good.
29.10.2019 03:14, Dmitry Osipenko пишет: > 28.10.2019 17:27, Peter De Schrijver пишет: >> On Tue, Jul 23, 2019 at 05:52:44AM +0300, Dmitry Osipenko wrote: >>> Unset "enable" bit means that divider is in bypass mode, hence it doesn't >>> have any effect in that case. Please note that there are no known bugs >>> caused by the missing check. >>> >> >> Technically this is not quite true, but for the purposes of CCF you can >> treat it that way. This bits defines if the value in the lower 16 bits >> of the divider register is used to configure the divider or if the >> contents of the UART DLM/DLL registers is used. So the divider isn't >> actually bypassed, it's just configured differently. >> In practice this bit is only set when the divider is non-zero when doing >> set rate. So the extra test isn't strictly needed as long as the sw >> running before the kernel also ensures the bit is only set when the >> divider is non-zero. >> >> Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com> > > Thank you for the clarification. I hope that bootloader doesn't enable > the divider because it looks like standard 8250 driver won't be ready > for that. But serial-tegra driver seems should be good. Actually, it should be good because I missed that UART clocks are per-initialized in the clk driver init table. I'll update commit's message and send a new version of this patch.
diff --git a/drivers/clk/tegra/clk-divider.c b/drivers/clk/tegra/clk-divider.c index e76731fb7d69..f33c19045386 100644 --- a/drivers/clk/tegra/clk-divider.c +++ b/drivers/clk/tegra/clk-divider.c @@ -40,8 +40,13 @@ static unsigned long clk_frac_div_recalc_rate(struct clk_hw *hw, int div, mul; u64 rate = parent_rate; - reg = readl_relaxed(divider->reg) >> divider->shift; - div = reg & div_mask(divider); + reg = readl_relaxed(divider->reg); + + if ((divider->flags & TEGRA_DIVIDER_UART) && + !(reg & PERIPH_CLK_UART_DIV_ENB)) + return rate; + + div = (reg >> divider->shift) & div_mask(divider); mul = get_mul(divider); div += mul;
Unset "enable" bit means that divider is in bypass mode, hence it doesn't have any effect in that case. Please note that there are no known bugs caused by the missing check. Signed-off-by: Dmitry Osipenko <digetx@gmail.com> --- Changelog: v2: Changed the commit's description from 'Fix' to 'Add' in response to the Stephen's Boyd question about the need to backport the patch into stable kernels. The backporting is not really needed. drivers/clk/tegra/clk-divider.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)