Re: [RFC,v2,1/8] video: tegra: Add nvhost driver

On 29.11.2012 11:10, Mark Zhang wrote:

...

+/**

• • Write a cpu syncpoint increment to the hardware, without touching
• • the cache. Caller is responsible for host being powered.
• */

+static void host1x_syncpt_cpu_incr(struct nvhost_syncpt *sp, u32 id) +{

• struct nvhost_master *dev = syncpt_to_dev(sp);
  

• u32 reg_offset = id / 32;
  

• if (!nvhost_module_powered(dev->dev)) {
  

•         dev_err(&syncpt_to_dev(sp)->dev->dev,
  

•                 "Trying to access host1x when it's off");
  

•         return;
  

• }
  

• if (!nvhost_syncpt_client_managed(sp, id)
  

•                 && nvhost_syncpt_min_eq_max(sp, id)) {
  

•         dev_err(&syncpt_to_dev(sp)->dev->dev,
  

•                 "Trying to increment syncpoint id %d beyond max\n",
  

•                 id);
  

•         return;
  

• }
  

• writel(BIT_MASK(id), dev->sync_aperture +
  

•                 host1x_sync_syncpt_cpu_incr_r() + reg_offset * 4);
  

I have a stupid question: According to the name and the context of this function, seems it increases the syncpt value which specified by param "id". So how does this "writel" increase the value? I don't know much about host1x/syncpt reg operations, so could you explain a little bit or I just completely have a wrong understanding?

I believe I've implemented most of the requests in this mail, but I seem to have missed answering this question.

writel() to that register invokes a method in host1x, which increments the sync point indicated by the value of the register by one.

Best regards, Terje