From mboxrd@z Thu Jan 1 00:00:00 1970 From: linus.walleij@linaro.org (Linus Walleij) Date: Thu, 5 Jul 2012 00:09:32 +0200 Subject: [PATCH] clk: allow clocks without parents to change rate Message-ID: <1341439772-649-1-git-send-email-linus.walleij@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org The clk_change_rate() code would dereference clk->parent to get clk->parent->rate without first checking that clk->parent was valid. This doesn't work if the clock is (A) a root clock and (B) can change rate. Such is the case with a VCO clock like the ICST which consequently crash like this without this patch: Unable to handle kernel NULL pointer dereference at virtual address 0000001c pgd = c0004000 [0000001c] *pgd=00000000 Internal error: Oops: 5 [#1] PREEMPT ARM Modules linked in: CPU: 0 Not tainted (3.5.0-rc3-00003-g8156866-dirty #193) PC is at clk_change_rate+0x34/0xd8 LR is at clk_change_rate+0x18/0xd8 Cc: stable at kernel.org Cc: Mike Turquette Cc: Ulf Hansson Signed-off-by: Linus Walleij --- drivers/clk/clk.c | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 687b00d..032d79c 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -854,14 +854,22 @@ static void clk_change_rate(struct clk *clk) old_rate = clk->rate; - if (clk->ops->set_rate) - clk->ops->set_rate(clk->hw, clk->new_rate, clk->parent->rate); + if (clk->ops->set_rate) { + if (clk->parent) + clk->ops->set_rate(clk->hw, clk->new_rate, + clk->parent->rate); + else + clk->ops->set_rate(clk->hw, clk->new_rate, 0); + } - if (clk->ops->recalc_rate) - clk->rate = clk->ops->recalc_rate(clk->hw, - clk->parent->rate); - else - clk->rate = clk->parent->rate; + if (clk->ops->recalc_rate) { + if (clk->parent) + clk->rate = clk->ops->recalc_rate(clk->hw, + clk->parent->rate); + else + clk->rate = clk->ops->recalc_rate(clk->hw, 0); + } else + clk->rate = clk->parent ? clk->parent->rate : 0; if (clk->notifier_count && old_rate != clk->rate) __clk_notify(clk, POST_RATE_CHANGE, old_rate, clk->rate); -- 1.7.10.4