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    SubjectRe: [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


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