Hi Javier,
On Thursday 05 May 2011 15:53:08 Javier Martin wrote:
> Do not use omap3isp_get() when what we really want to do is just
> enable clocks, since omap3isp_get() has additional, unwanted, side
> effects as an increase of the counter.
>
> This prevented omap3isp of working with Beagleboard xM and it has
> been tested only with that platform + mt9p031 sensor.
>
> Signed-off-by: Javier Martin <javier.martin@xxxxxxxxxxxxxxxxx>
> ---
> drivers/media/video/omap3isp/isp.c | 8 +++++---
> 1 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/video/omap3isp/isp.c
> b/drivers/media/video/omap3isp/isp.c index 472a693..ca0831f 100644
> --- a/drivers/media/video/omap3isp/isp.c
> +++ b/drivers/media/video/omap3isp/isp.c
> @@ -85,9 +85,11 @@ module_param(autoidle, int, 0444);
> MODULE_PARM_DESC(autoidle, "Enable OMAP3ISP AUTOIDLE support");
>
> static void isp_save_ctx(struct isp_device *isp);
> -
> static void isp_restore_ctx(struct isp_device *isp);
>
> +static int isp_enable_clocks(struct isp_device *isp);
> +static void isp_disable_clocks(struct isp_device *isp);
> +
> static const struct isp_res_mapping isp_res_maps[] = {
> {
> .isp_rev = ISP_REVISION_2_0,
> @@ -239,10 +241,10 @@ static u32 isp_set_xclk(struct isp_device *isp, u32
> xclk, u8 xclksel)
>
> /* Do we go from stable whatever to clock? */
> if (divisor >= 2 && isp->xclk_divisor[xclksel - 1] < 2)
> - omap3isp_get(isp);
> + isp_enable_clocks(isp);
This won't work. Let's assume the following sequence of events:
- Userspace opens the sensor subdev device node
- The sensor driver calls to board code to turn the sensor clock on
- Board code calls to the ISP driver to turn XCLK on
- The ISP driver calls isp_enable_clocks()
...
- Userspace opens an ISP video device node
- The ISP driver calls isp_get(), incrementing the reference count
- Userspace closes the ISP video device node
- The ISP driver calls isp_put(), decrementing the reference count
- The reference count reaches 0, the ISP driver calls isp_disable_clocks()
The sensor will then loose its clock, even though the sensor subdev device
node is still opened.
Could you please explain why the existing code doesn't work on your hardware ?
> /* Stopping the clock. */
> else if (divisor < 2 && isp->xclk_divisor[xclksel - 1] >= 2)
> - omap3isp_put(isp);
> + isp_disable_clocks(isp);
>
> isp->xclk_divisor[xclksel - 1] = divisor;
--
Regards,
Laurent Pinchart
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