On 3/13/22 8:41 AM, Noralf Trønnes wrote:
Den 13.03.2022 15.10, skrev trix@xxxxxxxxxx:
From: Tom Rix <trix@xxxxxxxxxx>
repaper_spi_transfer() allocates a single byte
for the spi header and then another buffer for
the payload. Combine the allocs into a single
buffer with offsets. To simplify the offsets
put the header after the payload.
Signed-off-by: Tom Rix <trix@xxxxxxxxxx>
---
drivers/gpu/drm/tiny/repaper.c | 40 ++++++++++------------------------
1 file changed, 12 insertions(+), 28 deletions(-)
diff --git a/drivers/gpu/drm/tiny/repaper.c b/drivers/gpu/drm/tiny/repaper.c
index 37b6bb90e46e1..22a6732f35a01 100644
--- a/drivers/gpu/drm/tiny/repaper.c
+++ b/drivers/gpu/drm/tiny/repaper.c
@@ -100,50 +100,34 @@ static inline struct repaper_epd *drm_to_epd(struct drm_device *drm)
static int repaper_spi_transfer(struct spi_device *spi, u8 header,
const void *tx, void *rx, size_t len)
{
- void *txbuf = NULL, *rxbuf = NULL;
struct spi_transfer tr[2] = {};
- u8 *headerbuf;
+ u8 *buf;
int ret;
- headerbuf = kmalloc(1, GFP_KERNEL);
- if (!headerbuf)
+ buf = kmalloc(1 + len, GFP_KERNEL);
+ if (!buf)
return -ENOMEM;
- headerbuf[0] = header;
- tr[0].tx_buf = headerbuf;
+ buf[len] = header;
+ tr[0].tx_buf = &buf[len];
I don't think this will work since the buffer is used directly for DMA
on some platforms[1] so the buffers need to be at the correct alignment
for that to work. For this reason I think it's better to leave this
as-is since we know the kmalloc buffers will always be useable for DMA
and the code is also easy to read and understand instead of calculating
offsets.
[1] tinydrm/mipi-dbi: Use dma-safe buffers for all SPI transfers
(a89bfc5d9a07)
Noralf.
tr[0].len = 1;
- /* Stack allocated tx? */
- if (tx && len <= 32) {
How about a change to remove this ?
It seems like you are getting lucky.
reduce the to single txrx_buf
Tom
- txbuf = kmemdup(tx, len, GFP_KERNEL);
- if (!txbuf) {
- ret = -ENOMEM;
- goto out_free;
- }
+ if (tx) {
+ memcpy(buf, tx, len);
+ tr[1].tx_buf = buf;
}
- if (rx) {
- rxbuf = kmalloc(len, GFP_KERNEL);
- if (!rxbuf) {
- ret = -ENOMEM;
- goto out_free;
- }
- }
+ if (rx)
+ tr[1].rx_buf = buf;
- tr[1].tx_buf = txbuf ? txbuf : tx;
- tr[1].rx_buf = rxbuf;
tr[1].len = len;
ndelay(80);
ret = spi_sync_transfer(spi, tr, 2);
if (rx && !ret)
- memcpy(rx, rxbuf, len);
-
-out_free:
- kfree(headerbuf);
- kfree(txbuf);
- kfree(rxbuf);
+ memcpy(rx, buf, len);
+ kfree(buf);
return ret;
}
