On Wed, Sep 3, 2014 at 4:36 AM, Anson Huang <b20788@xxxxxxxxxxxxx> wrote: > Currently, gpt timer's clock is from ipg_per, and ipg_per clock is from ipg > on most of i.MX6 series SOCs, but ipg's rate may be scaled when system enters > low bus mode for saving power, then gpt timer's clock rate will be scaled as > well, as system timer should be kept stable and NOT drift, better to keep gpt > timer's clk at fixed rate, on i.MX6Q TO > 1.0, i.MX6DL and i.MX6SX, there is > OSC clk available for gpt timer, we should enable this feature, the hardware > design is as below: > > i.MX6Q TO > 1.0: GPT_CR_CLKSRC, 3b'101 selects fix clock > of OSC / 8 for gpt per clk; > i.MX6DL and i.MX6SX: GPT_CR_CLKSRC, 3b'101 selects OSC > for gpt per clk, and we must enable GPT_CR_24MEM to > enable OSC clk source for gpt per, GPT_PR_PRESCALER24M > is for pre-scaling of this OSC clk, here set it to 8 > to make gpt per clk is 3MHz; > i.MX6SL: ipg_per can be from OSC directly, so no need to > implement this new clk source for gpt per. > > Anson Huang (3): > ARM: imx: add gpt_3m clk for i.mx6qdl > ARM: dts: imx6: change gpt per clk to gpt_3m on i.mx6qdl and i.mx6sx > ARM: imx: source gpt per clk from OSC for system timer This patch series works fine if we use the new dtb and new kernel. However, booting a kernel with these series applied and using an old dtb we get a system with broken timer. 'sleep 1' takes something like 20 seconds in this case. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
