| Message ID | 1421767964-8798-2-git-send-email-peter.griffin@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Quoting Peter Griffin (2015-01-20 07:32:41) > Debugging eMMC on upstream kernels it has been noticed that when the > targetpack configures MMC0 clock to 200Mhz (required to switch to > HS200) then everything works OK. However if the kernel sets the > clock rate using clk_set_rate, then the eMMC card initialisation > fails with timeouts. Lower clock speeds (the default being 50Mhz) > work ok, but they we fail to get good eMMC transfer rates. > > Looking through the vendor kernel clock driver reveals Giuseppe > had already fixed this issue, but the patch hasn't made its way > upstream. > > The issue is fixed by changing the logic to manage the pdiv and > fdiv divisors used for setting the rate inside the flexgen driver code. > > Pdiv is mainly targeted for low freq results, while fdiv should be > used for divs =< 64. The other way can lead to 'duty cycle' > issues. > > I have changed the original patch to keep the original behaviour > in cases where the div is >64 which matches the original comment > and patch description more closely. Although no clocks appear to hit > this case currently when booting an upstream kernel. > > Signed-off-by: Peter Griffin <peter.griffin@linaro.org> > Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com> Applied to clk-next. Regards, Mike > --- > drivers/clk/st/clk-flexgen.c | 19 +++++++++++++++---- > 1 file changed, 15 insertions(+), 4 deletions(-) > > diff --git a/drivers/clk/st/clk-flexgen.c b/drivers/clk/st/clk-flexgen.c > index 2282cef..3a484b3 100644 > --- a/drivers/clk/st/clk-flexgen.c > +++ b/drivers/clk/st/clk-flexgen.c > @@ -138,16 +138,27 @@ static int flexgen_set_rate(struct clk_hw *hw, unsigned long rate, > struct flexgen *flexgen = to_flexgen(hw); > struct clk_hw *pdiv_hw = &flexgen->pdiv.hw; > struct clk_hw *fdiv_hw = &flexgen->fdiv.hw; > - unsigned long primary_div = 0; > + unsigned long div = 0; > int ret = 0; > > pdiv_hw->clk = hw->clk; > fdiv_hw->clk = hw->clk; > > - primary_div = clk_best_div(parent_rate, rate); > + div = clk_best_div(parent_rate, rate); > > - clk_divider_ops.set_rate(fdiv_hw, parent_rate, parent_rate); > - ret = clk_divider_ops.set_rate(pdiv_hw, rate, rate * primary_div); > + /* > + * pdiv is mainly targeted for low freq results, while fdiv > + * should be used for div <= 64. The other way round can > + * lead to 'duty cycle' issues. > + */ > + > + if (div <= 64) { > + clk_divider_ops.set_rate(pdiv_hw, parent_rate, parent_rate); > + ret = clk_divider_ops.set_rate(fdiv_hw, rate, rate * div); > + } else { > + clk_divider_ops.set_rate(fdiv_hw, parent_rate, parent_rate); > + ret = clk_divider_ops.set_rate(pdiv_hw, rate, rate * div); > + } > > return ret; > } > -- > 1.9.1 > -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/clk/st/clk-flexgen.c b/drivers/clk/st/clk-flexgen.c index 2282cef..3a484b3 100644 --- a/drivers/clk/st/clk-flexgen.c +++ b/drivers/clk/st/clk-flexgen.c @@ -138,16 +138,27 @@ static int flexgen_set_rate(struct clk_hw *hw, unsigned long rate, struct flexgen *flexgen = to_flexgen(hw); struct clk_hw *pdiv_hw = &flexgen->pdiv.hw; struct clk_hw *fdiv_hw = &flexgen->fdiv.hw; - unsigned long primary_div = 0; + unsigned long div = 0; int ret = 0; pdiv_hw->clk = hw->clk; fdiv_hw->clk = hw->clk; - primary_div = clk_best_div(parent_rate, rate); + div = clk_best_div(parent_rate, rate); - clk_divider_ops.set_rate(fdiv_hw, parent_rate, parent_rate); - ret = clk_divider_ops.set_rate(pdiv_hw, rate, rate * primary_div); + /* + * pdiv is mainly targeted for low freq results, while fdiv + * should be used for div <= 64. The other way round can + * lead to 'duty cycle' issues. + */ + + if (div <= 64) { + clk_divider_ops.set_rate(pdiv_hw, parent_rate, parent_rate); + ret = clk_divider_ops.set_rate(fdiv_hw, rate, rate * div); + } else { + clk_divider_ops.set_rate(fdiv_hw, parent_rate, parent_rate); + ret = clk_divider_ops.set_rate(pdiv_hw, rate, rate * div); + } return ret; }