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dmaengine: dmatest: prevent using swiotlb buffer with nobounce parameter

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Source and destination data buffers are allocated with GPF_KERNEL flag.
It means that, if the DDR is more than 2GB, buffers can be allocated above
the 32-bit addressable space. In this case, and if the dma controller is
only 32-bit compatible, swiotlb bounce buffer, located in the 32-bit
addressable space, is used and introduces a memcpy.

To prevent this extra memcpy, due to swiotlb bounce buffer use because
source or destination data buffer is allocated above the 32-bit addressable
space, force source and destination data buffers allocation with GPF_DMA
instead, when nobounce parameter is true.

Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/20231124160235.2459326-1-amelie.delaunay@foss.st.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
This commit is contained in:
Amelie Delaunay 2023-11-24 17:02:35 +01:00 committed by Vinod Koul
parent 25b636225a
commit 70f008fb3e
1 changed files with 16 additions and 1 deletions
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17
drivers/dma/dmatest.c
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@ -21,6 +21,10 @@
#include <linux/slab.h>
#include <linux/wait.h>
static bool nobounce;
module_param(nobounce, bool, 0644);
MODULE_PARM_DESC(nobounce, "Prevent using swiotlb buffer (default: use swiotlb buffer)");
static unsigned int test_buf_size = 16384;
module_param(test_buf_size, uint, 0644);
MODULE_PARM_DESC(test_buf_size, "Size of the memcpy test buffer");
@ -90,6 +94,7 @@ MODULE_PARM_DESC(polled, "Use polling for completion instead of interrupts");
/**
* struct dmatest_params - test parameters.
* @nobounce: prevent using swiotlb buffer
* @buf_size: size of the memcpy test buffer
* @channel: bus ID of the channel to test
* @device: bus ID of the DMA Engine to test
@ -106,6 +111,7 @@ MODULE_PARM_DESC(polled, "Use polling for completion instead of interrupts");
* @polled: use polling for completion instead of interrupts
*/
struct dmatest_params {
bool nobounce;
unsigned int buf_size;
char channel[20];
char device[32];
@ -215,6 +221,7 @@ struct dmatest_done {
struct dmatest_data {
u8 **raw;
u8 **aligned;
gfp_t gfp_flags;
unsigned int cnt;
unsigned int off;
};
@ -533,7 +540,7 @@ static int dmatest_alloc_test_data(struct dmatest_data *d,
goto err;
for (i = 0; i < d->cnt; i++) {
d->raw[i] = kmalloc(buf_size + align, GFP_KERNEL);
d->raw[i] = kmalloc(buf_size + align, d->gfp_flags);
if (!d->raw[i])
goto err;
@ -655,6 +662,13 @@ static int dmatest_func(void *data)
goto err_free_coefs;
}
src->gfp_flags = GFP_KERNEL;
dst->gfp_flags = GFP_KERNEL;
if (params->nobounce) {
src->gfp_flags = GFP_DMA;
dst->gfp_flags = GFP_DMA;
}
if (dmatest_alloc_test_data(src, buf_size, align) < 0)
goto err_free_coefs;
@ -1093,6 +1107,7 @@ static void add_threaded_test(struct dmatest_info *info)
struct dmatest_params *params = &info->params;
/* Copy test parameters */
params->nobounce = nobounce;
params->buf_size = test_buf_size;
strscpy(params->channel, strim(test_channel), sizeof(params->channel));
strscpy(params->device, strim(test_device), sizeof(params->device));