Re: [PATCH 01/11] clk: sunxi-ng: Don't set k if width is 0 for nkmp plls

On Sun, Dec 31, 2017 at 5:01 AM, Jernej Skrabec jernej.skrabec@siol.net wrote:

For example, A83T have nmp plls which are modelled as nkmp plls. Since k is not specified, it has offset 0, shift 0 and lowest value 1. This means that LSB bit is always set to 1, which may change clock rate.

Fix that by applying k factor only if k width is greater than 0.

Signed-off-by: Jernej Skrabec jernej.skrabec@siol.net

drivers/clk/sunxi-ng/ccu_nkmp.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/clk/sunxi-ng/ccu_nkmp.c b/drivers/clk/sunxi-ng/ccu_nkmp.c index e58c95787f94..709f528af2b3 100644 --- a/drivers/clk/sunxi-ng/ccu_nkmp.c +++ b/drivers/clk/sunxi-ng/ccu_nkmp.c @@ -81,7 +81,7 @@ static unsigned long ccu_nkmp_recalc_rate(struct clk_hw *hw, unsigned long parent_rate) { struct ccu_nkmp *nkmp = hw_to_ccu_nkmp(hw);

•   unsigned long n, m, k, p;
  

•   unsigned long n, m, k = 1, p;
    u32 reg;
  
    reg = readl(nkmp->common.base + nkmp->common.reg);
  

@@ -92,11 +92,13 @@ static unsigned long ccu_nkmp_recalc_rate(struct clk_hw *hw, if (!n) n++;

•   k = reg >> nkmp->k.shift;
  

•   k &= (1 << nkmp->k.width) - 1;
  

•   k += nkmp->k.offset;
  

•   if (!k)
  

•           k++;
  

•   if (nkmp->k.width) {
  

•           k = reg >> nkmp->k.shift;
  

•           k &= (1 << nkmp->k.width) - 1;
  

•           k += nkmp->k.offset;
  

•           if (!k)
  

•                   k++;
  

•   }
  

The conditional shouldn't be necessary. With nkmp->k.width = 0, you'd simply get k & 0, which is 0, which then gets bumped up to 1, unless k.offset > 1, which would be a bug.

    m = reg >> nkmp->m.shift;
    m &= (1 << nkmp->m.width) - 1;

@@ -153,12 +155,15 @@ static int ccu_nkmp_set_rate(struct clk_hw *hw, unsigned long rate,

    reg = readl(nkmp->common.base + nkmp->common.reg);
    reg &= ~GENMASK(nkmp->n.width + nkmp->n.shift - 1, nkmp->n.shift);

•   reg &= ~GENMASK(nkmp->k.width + nkmp->k.shift - 1, nkmp->k.shift);
  

•   if (nkmp->k.width)
  

•           reg &= ~GENMASK(nkmp->k.width + nkmp->k.shift - 1,
  

•                           nkmp->k.shift);
    reg &= ~GENMASK(nkmp->m.width + nkmp->m.shift - 1, nkmp->m.shift);
    reg &= ~GENMASK(nkmp->p.width + nkmp->p.shift - 1, nkmp->p.shift);
  
    reg |= (_nkmp.n - nkmp->n.offset) << nkmp->n.shift;
  

•   reg |= (_nkmp.k - nkmp->k.offset) << nkmp->k.shift;
  

•   if (nkmp->k.width)
  

•           reg |= (_nkmp.k - nkmp->k.offset) << nkmp->k.shift;
  

I think a better way would be

reg |= ((_nkmp.k - nkmp->k.offset) << nkmp->k.shift) & GENMASK(nkmp->k.width + nkmp->k.shift - 1, nkmp->k.shift);

And do this for all the factors, not just k. This pattern is what regmap_update_bits does, which seems much safer. I wonder what GENMASK() with a negative value would do though...

ChenYu

    reg |= (_nkmp.m - nkmp->m.offset) << nkmp->m.shift;
    reg |= ilog2(_nkmp.p) << nkmp->p.shift;

-- 2.15.1