Re: [PATCH 02/17] fpga: dfl: fme: align PR buffer size per PR datawidth

On Mon, Mar 25, 2019 at 12:50:40PM -0500, Alan Tull wrote:

On Sun, Mar 24, 2019 at 10:23 PM Wu Hao [off-list ref] wrote:

Hi Hao,

Looks good, one question below.

quoted

Current driver checks if input bitstream file size is aligned or
not per PR data width (default 32bits). It requires one additional
step for end user when they generate the bitstream file, padding
extra zeros to bitstream file to align its size per PR data width,
but they don't have to as hardware will drop extra padding bytes
automatically.

In order to simplify the user steps, this patch aligns PR buffer
size per PR data width in driver, to allow user to pass unaligned
size bitstream files to driver.

Signed-off-by: Xu Yilun <yilun.xu@intel.com>
Signed-off-by: Wu Hao <redacted>
---
 drivers/fpga/dfl-fme-pr.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/fpga/dfl-fme-pr.c b/drivers/fpga/dfl-fme-pr.c
index d9ca955..c1fb1fe 100644
--- a/drivers/fpga/dfl-fme-pr.c
+++ b/drivers/fpga/dfl-fme-pr.c

@@ -74,6 +74,7 @@ static int fme_pr(struct platform_device *pdev, unsigned long arg)
        struct dfl_fme *fme;
        unsigned long minsz;
        void *buf = NULL;
+       size_t length;
        int ret = 0;
        u64 v;

@@ -85,9 +86,6 @@ static int fme_pr(struct platform_device *pdev, unsigned long arg)
        if (port_pr.argsz < minsz || port_pr.flags)
                return -EINVAL;

-       if (!IS_ALIGNED(port_pr.buffer_size, 4))
-               return -EINVAL;
-
        /* get fme header region */
        fme_hdr = dfl_get_feature_ioaddr_by_id(&pdev->dev,
                                               FME_FEATURE_ID_HEADER);

@@ -103,7 +101,13 @@ static int fme_pr(struct platform_device *pdev, unsigned long arg)
                       port_pr.buffer_size))
                return -EFAULT;

-       buf = vmalloc(port_pr.buffer_size);
+       /*
+        * align PR buffer per PR bandwidth, as HW ignores the extra padding
+        * data automatically.
+        */
+       length = ALIGN(port_pr.buffer_size, 4);
+
+       buf = vmalloc(length);

Since it may not be completely filled, would it be worthwhile to alloc
a zero'ed buff?

Hi Alan,

Thanks for the review, acutally per spec, hw doesn't care about the
extra padding data. So for now, i guess we don't need this.

Thanks
Hao

Alan