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SubjectRe: [PATCH v4 12/21] camss: vfe: Format conversion support using PIX interface
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Hi Geert,

On 10.09.2017 12:58, Geert Uytterhoeven wrote:
> Hi Todor,
>
> On Tue, Aug 8, 2017 at 3:30 PM, Todor Tomov <todor.tomov@linaro.org> wrote:
>> Use VFE PIX input interface and do format conversion in VFE.
>>
>> Supported input format is UYVY (single plane YUV 4:2:2) and
>> its different sample order variations.
>>
>> Supported output formats are:
>> - NV12/NV21 (two plane YUV 4:2:0)
>> - NV16/NV61 (two plane YUV 4:2:2)
>>
>> Signed-off-by: Todor Tomov <todor.tomov@linaro.org>
>
> This is now commit 9b5833f7b82f1431 upstream.
>
>> @@ -355,6 +471,38 @@ static void vfe_bus_disconnect_wm_from_rdi(struct vfe_device *vfe, u8 wm,
>> vfe_reg_clr(vfe, VFE_0_BUS_XBAR_CFG_x(wm), reg);
>> }
>>
>> +static void vfe_set_xbar_cfg(struct vfe_device *vfe, struct vfe_output *output,
>> + u8 enable)
>> +{
>> + struct vfe_line *line = container_of(output, struct vfe_line, output);
>> + u32 p = line->video_out.active_fmt.fmt.pix_mp.pixelformat;
>> + u32 reg;
>
> With gcc 4.1.2:
>
> drivers/media/platform/qcom/camss-8x16/camss-vfe.c: In function
> ‘vfe_set_xbar_cfg’:
> drivers/media/platform/qcom/camss-8x16/camss-vfe.c:614: warning:
> ‘reg’ may be used uninitialized in this function
>
> This is a false positive, as output->wm_num is always either 1 or 2, hence the
> index i can never have a value different from 0 or 1, and reg is thus always
> initialized.
>
>> + unsigned int i;
>> +
>> + for (i = 0; i < output->wm_num; i++) {
>> + if (i == 0) {
>> + reg = VFE_0_BUS_XBAR_CFG_x_M_SINGLE_STREAM_SEL_LUMA <<
>> + VFE_0_BUS_XBAR_CFG_x_M_SINGLE_STREAM_SEL_SHIFT;
>> + } else if (i == 1) {
>> + reg = VFE_0_BUS_XBAR_CFG_x_M_PAIR_STREAM_EN;
>> + if (p == V4L2_PIX_FMT_NV12 || p == V4L2_PIX_FMT_NV16)
>> + reg |= VFE_0_BUS_XBAR_CFG_x_M_PAIR_STREAM_SWAP_INTER_INTRA;
>> + }
>
>> @@ -458,6 +728,10 @@ static void vfe_init_outputs(struct vfe_device *vfe)
>> output->buf[0] = NULL;
>> output->buf[1] = NULL;
>> INIT_LIST_HEAD(&output->pending_bufs);
>> +
>> + output->wm_num = 1;
>> + if (vfe->line[i].id == VFE_LINE_PIX)
>> + output->wm_num = 2;
>> }
>> }
>>
>
>> --- a/drivers/media/platform/qcom/camss-8x16/camss-vfe.h
>> +++ b/drivers/media/platform/qcom/camss-8x16/camss-vfe.h
>> @@ -30,8 +30,9 @@
>> #define MSM_VFE_PAD_SRC 1
>> #define MSM_VFE_PADS_NUM 2
>>
>> -#define MSM_VFE_LINE_NUM 3
>> +#define MSM_VFE_LINE_NUM 4
>> #define MSM_VFE_IMAGE_MASTERS_NUM 7
>> +#define MSM_VFE_COMPOSITE_IRQ_NUM 4
>>
>> #define MSM_VFE_VFE0_UB_SIZE 1023
>> #define MSM_VFE_VFE0_UB_SIZE_RDI (MSM_VFE_VFE0_UB_SIZE / 3)
>> @@ -51,11 +52,13 @@ enum vfe_line_id {
>> VFE_LINE_NONE = -1,
>> VFE_LINE_RDI0 = 0,
>> VFE_LINE_RDI1 = 1,
>> - VFE_LINE_RDI2 = 2
>> + VFE_LINE_RDI2 = 2,
>> + VFE_LINE_PIX = 3
>> };
>>
>> struct vfe_output {
>> - u8 wm_idx;
>> + u8 wm_num;
>> + u8 wm_idx[3];
>
> However, wm_idx[] reserves space for 3 entries, while currently only 2 are
> needed. Why?
>
> If this is meant to accommodate for a future extension, the false positive
> will become a real issue.

The third entry will be needed if we add any three planar pixel format support
to the driver. If this happens this will involve also changes in
vfe_set_xbar_cfg() to support it. It is fine to change wm_idx[3] to wm_idx[2]
until then. However this will not remove the false positive warning. I suppose
it is best to also change vfe_set_xbar_cfg() now so that there is no warning -
init reg to 0 in all cases?

>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> -- Linus Torvalds
>

--
Best regards,
Todor Tomov

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