Hi Martin, > Martin Sperl <kernel@xxxxxxxxxxxxxxxx> hat am 16. Februar 2016 um 17:31 > geschrieben: > > > > > On 13.02.2016, at 21:45, Stefan Wahren <stefan.wahren@xxxxxxxx> wrote: > > > > > > According to the datasheet busy bit shouldn't be set while changing the > > clock. > > So this isn't good. I hope this could be fixed, too. > > > > I had hoped that the patch by Eric: > "clk: bcm2835: Fix setting of PLL divider clock rates" > would fix the issue, but that was unfortunately not the case. > > Some more investigation using the debugfs patch I had posted, > which exposes the registers showed that: > plld_per_a2w had a value of 4 before starting getty > and a value of 0 after starting getty. > > That made me investigate why this value was changed and I found > the culprit in the form of: > @@ -1167,7 +1171,9 @@ static void bcm2835_pll_divider_off(struct clk_hw *hw) > cprman_write(cprman, data->cm_reg, > (cprman_read(cprman, data->cm_reg) & > ~data->load_mask) | data->hold_mask); > - cprman_write(cprman, data->a2w_reg, A2W_PLL_CHANNEL_DISABLE); > + cprman_write(cprman, data->a2w_reg, > + cprman_read(cprman, data->a2w_reg) | > + A2W_PLL_CHANNEL_DISABLE); > } good job. This change make sense because the divider value shouldn't be zero. But maybe we should protect the RMW by a lock like in bcm2835_clock_off? > > after that (with plld itself marked as “prepared” during probe) everything is > working fine. > > bcm2835_pll_off shows a similar pattern, but patching that > the same way: > @@ -955,8 +955,12 @@ static void bcm2835_pll_off(struct clk_hw *hw) > struct bcm2835_cprman *cprman = pll->cprman; > const struct bcm2835_pll_data *data = pll->data; > > - cprman_write(cprman, data->cm_ctrl_reg, CM_PLL_ANARST); > - cprman_write(cprman, data->a2w_ctrl_reg, A2W_PLL_CTRL_PWRDN); > + cprman_write(cprman, data->cm_ctrl_reg, > + cprman_read(cprman, data->cm_ctrl_reg) | > + CM_PLL_ANARST); > + cprman_write(cprman, data->a2w_ctrl_reg, > + cprman_read(cprman, data->a2w_ctrl_reg) | > + A2W_PLL_CTRL_PWRDN); > } > > does not resolve the issue - the system crashes - but without he pll > lock message… Without the knowledge about the registers it's hard to say what exactly causes the crash. Regards Stefan -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
