Re: [PATCH v5 07/14] media: ti: j721e-csi2rx: get number of contexts from device tree

[Jai Luthra <jai.luthra@ideasonboard.com>]

Hi Rishikesh,

Quoting Rishikesh Donadkar (2025-08-25 19:55:15)
> From: Pratyush Yadav <p.yadav@ti.com>
> 
> Different platforms that use this driver might have different number of
> DMA channels allocated for CSI. So only as many DMA contexts can be used
> as the number of DMA channels available. Get the number of channels
> provided via device tree and only configure that many contexts, and
> hence only that many pads.
> 
> Reviewed-by: Yemike Abhilash Chandra <y-abhilashchandra@ti.com>
> Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
> Co-developed-by: Jai Luthra <j-luthra@ti.com>
> Signed-off-by: Jai Luthra <j-luthra@ti.com>
> Signed-off-by: Rishikesh Donadkar <r-donadkar@ti.com>
> ---
>  .../platform/ti/j721e-csi2rx/j721e-csi2rx.c   | 42 ++++++++++++++-----
>  1 file changed, 31 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
> index 4e1c9db0dcf5..6cab7642aa10 100644
> --- a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
> +++ b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
> @@ -44,7 +44,7 @@
>  
>  #define TI_CSI2RX_MAX_PIX_PER_CLK      4
>  #define PSIL_WORD_SIZE_BYTES           16
> -#define TI_CSI2RX_NUM_CTX              1
> +#define TI_CSI2RX_MAX_CTX              32
>  
>  /*
>   * There are no hard limits on the width or height. The DMA engine can handle
> @@ -57,8 +57,8 @@
>  
>  #define TI_CSI2RX_PAD_SINK             0
>  #define TI_CSI2RX_PAD_FIRST_SOURCE     1
> -#define TI_CSI2RX_NUM_SOURCE_PADS      1
> -#define TI_CSI2RX_NUM_PADS             (1 + TI_CSI2RX_NUM_SOURCE_PADS)
> +#define TI_CSI2RX_MAX_SOURCE_PADS      TI_CSI2RX_MAX_CTX
> +#define TI_CSI2RX_MAX_PADS             (1 + TI_CSI2RX_MAX_SOURCE_PADS)
>  
>  #define DRAIN_TIMEOUT_MS               50
>  #define DRAIN_BUFFER_SIZE              SZ_32K
> @@ -118,14 +118,15 @@ struct ti_csi2rx_dev {
>         void __iomem                    *shim;
>         struct mutex                    mutex; /* To serialize ioctls. */
>         unsigned int                    enable_count;
> +       unsigned int                    num_ctx;
>         struct v4l2_device              v4l2_dev;
>         struct media_device             mdev;
>         struct media_pipeline           pipe;
> -       struct media_pad                pads[TI_CSI2RX_NUM_PADS];
> +       struct media_pad                pads[TI_CSI2RX_MAX_PADS];
>         struct v4l2_async_notifier      notifier;
>         struct v4l2_subdev              *source;
>         struct v4l2_subdev              subdev;
> -       struct ti_csi2rx_ctx            ctx[TI_CSI2RX_NUM_CTX];
> +       struct ti_csi2rx_ctx            ctx[TI_CSI2RX_MAX_CTX];
>         u8                              pix_per_clk;
>         /* Buffer to drain stale data from PSI-L endpoint */
>         struct {
> @@ -463,7 +464,7 @@ static int csi_async_notifier_complete(struct v4l2_async_notifier *notifier)
>                 return ret;
>  
>         /* Create and link video nodes for all DMA contexts */
> -       for (i = 0; i < TI_CSI2RX_NUM_CTX; i++) {
> +       for (i = 0; i < csi->num_ctx; i++) {
>                 struct ti_csi2rx_ctx *ctx = &csi->ctx[i];
>                 struct video_device *vdev = &ctx->vdev;
>  
> @@ -1250,10 +1251,11 @@ static int ti_csi2rx_v4l2_init(struct ti_csi2rx_dev *csi)
>         csi->pads[TI_CSI2RX_PAD_SINK].flags = MEDIA_PAD_FL_SINK;
>  
>         for (unsigned int i = TI_CSI2RX_PAD_FIRST_SOURCE;
> -            i < TI_CSI2RX_NUM_PADS; i++)
> +            i < TI_CSI2RX_PAD_FIRST_SOURCE + csi->num_ctx; i++)
>                 csi->pads[i].flags = MEDIA_PAD_FL_SOURCE;
>  
> -       ret = media_entity_pads_init(&sd->entity, ARRAY_SIZE(csi->pads),
> +       ret = media_entity_pads_init(&sd->entity,
> +                                    TI_CSI2RX_PAD_FIRST_SOURCE + csi->num_ctx,
>                                      csi->pads);
>         if (ret)
>                 goto unregister_media;
> @@ -1344,8 +1346,9 @@ static int ti_csi2rx_init_ctx(struct ti_csi2rx_ctx *ctx)
>  
>  static int ti_csi2rx_probe(struct platform_device *pdev)
>  {
> +       struct device_node *np = pdev->dev.of_node;
>         struct ti_csi2rx_dev *csi;
> -       int ret, i;
> +       int ret, i, count;
>  
>         csi = devm_kzalloc(&pdev->dev, sizeof(*csi), GFP_KERNEL);
>         if (!csi)
> @@ -1367,13 +1370,29 @@ static int ti_csi2rx_probe(struct platform_device *pdev)
>         if (!csi->drain.vaddr)
>                 return -ENOMEM;
>  
> +       /* Only use as many contexts as the number of DMA channels allocated. */
> +       count = of_property_count_strings(np, "dma-names");
> +       if (count < 0) {
> +               dev_err(csi->dev, "Failed to get DMA channel count: %d\n", count);
> +               ret = count;
> +               goto err_dma_chan;
> +       }
> +
> +       csi->num_ctx = count;
> +       if (csi->num_ctx > TI_CSI2RX_MAX_CTX) {
> +               dev_err(csi->dev,
> +                       "%u DMA channels passed. Maximum is %u.\n",
> +                       csi->num_ctx, TI_CSI2RX_MAX_CTX);
> +               goto err_dma_chan;
> +       }
> +

I get the following errors while compiling:

../drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c:1582:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
 1582 |         if (csi->num_ctx > TI_CSI2RX_MAX_CTX) {
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c:1627:9: note: uninitialized use occurs here
 1627 |         return ret;
      |                ^~~
../drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c:1582:2: note: remove the 'if' if its condition is always false
 1582 |         if (csi->num_ctx > TI_CSI2RX_MAX_CTX) {
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 1583 |                 dev_err(csi->dev,
      |                 ~~~~~~~~~~~~~~~~~
 1584 |                         "%u DMA channels passed. Maximum is %u.\n",
      |                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 1585 |                         csi->num_ctx, TI_CSI2RX_MAX_CTX);
      |                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 1586 |                 goto err_dma_chan;
      |                 ~~~~~~~~~~~~~~~~~~
 1587 |         }
      |         ~
../drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c:1551:9: note: initialize the variable 'ret' to silence this warning
 1551 |         int ret, i, count;
      |                ^
      |                 = 0

>         mutex_init(&csi->mutex);
>  
>         ret = ti_csi2rx_v4l2_init(csi);
>         if (ret)
>                 goto err_v4l2;
>  
> -       for (i = 0; i < TI_CSI2RX_NUM_CTX; i++) {
> +       for (i = 0; i < csi->num_ctx; i++) {
>                 csi->ctx[i].idx = i;
>                 csi->ctx[i].csi = csi;
>                 ret = ti_csi2rx_init_ctx(&csi->ctx[i]);
> @@ -1402,6 +1421,7 @@ static int ti_csi2rx_probe(struct platform_device *pdev)
>         ti_csi2rx_cleanup_v4l2(csi);
>  err_v4l2:
>         mutex_destroy(&csi->mutex);
> +err_dma_chan:
>         dma_free_coherent(csi->dev, csi->drain.len, csi->drain.vaddr,
>                           csi->drain.paddr);
>         return ret;
> @@ -1412,7 +1432,7 @@ static void ti_csi2rx_remove(struct platform_device *pdev)
>         struct ti_csi2rx_dev *csi = platform_get_drvdata(pdev);
>         unsigned int i;
>  
> -       for (i = 0; i < TI_CSI2RX_NUM_CTX; i++)
> +       for (i = 0; i < csi->num_ctx; i++)
>                 ti_csi2rx_cleanup_ctx(&csi->ctx[i]);
>  
>         ti_csi2rx_cleanup_notifier(csi);
> -- 
> 2.34.1
>