Re: [PATCH] spi: meson-spicc: add DMA support
From: neil . armstrong
Date: Mon Apr 14 2025 - 03:16:27 EST
On 14/04/2025 05:56, Da Xue wrote:
On Sun, Apr 13, 2025 at 11:14 PM Xianwei Zhao <xianwei.zhao@xxxxxxxxxxx> wrote:
Hi Neil,
Thanks for your reply.
On 2025/4/9 20:35, neil.armstrong@xxxxxxxxxx wrote:
Hi,
On 09/04/2025 03:49, Xianwei Zhao wrote:
Hi Neil,
Thanks for your reply.
On 2025/4/8 15:41, Neil Armstrong wrote:
[ EXTERNAL EMAIL ]
Hi,
On 08/04/2025 09:04, Xianwei Zhao via B4 Relay wrote:
From: Xianwei Zhao <xianwei.zhao@xxxxxxxxxxx>
Add DMA support for spicc driver.
DMA works if the transfer meets the following conditions:
1. 64 bits per word;
2. The transfer length must be multiples of the dma_burst_len,
and the dma_burst_len should be one of 8,7...2,
otherwise, it will be split into several SPI bursts.
Signed-off-by: Sunny Luo <sunny.luo@xxxxxxxxxxx>
Signed-off-by: Xianwei Zhao <xianwei.zhao@xxxxxxxxxxx>
---
drivers/spi/spi-meson-spicc.c | 243
++++++++++++++++++++++++++++++++++++++++--
1 file changed, 232 insertions(+), 11 deletions(-)
diff --git a/drivers/spi/spi-meson-spicc.c
b/drivers/spi/spi-meson-spicc.c
index df74ad5060f8..81e263bceba9 100644
--- a/drivers/spi/spi-meson-spicc.c
+++ b/drivers/spi/spi-meson-spicc.c
@@ -21,6 +21,7 @@
#include <linux/interrupt.h>
#include <linux/reset.h>
#include <linux/pinctrl/consumer.h>
+#include <linux/dma-mapping.h>
/*
* The Meson SPICC controller could support DMA based transfers,
but is not
@@ -33,6 +34,20 @@
* - CS management is dumb, and goes UP between every burst, so is
really a
* "Data Valid" signal than a Chip Select, GPIO link should be
used instead
* to have a CS go down over the full transfer
+ *
+ * DMA achieves a transfer with one or more SPI bursts, each SPI
burst is made
+ * up of one or more DMA bursts. The DMA burst implementation
mechanism is,
+ * For TX, when the number of words in TXFIFO is less than the preset
+ * reading threshold, SPICC starts a reading DMA burst, which reads
the preset
+ * number of words from TX buffer, then writes them into TXFIFO.
+ * For RX, when the number of words in RXFIFO is greater than the
preset
+ * writing threshold, SPICC starts a writing request burst, which
reads the
+ * preset number of words from RXFIFO, then write them into RX buffer.
+ * DMA works if the transfer meets the following conditions,
+ * - 64 bits per word
+ * - The transfer length in word must be multiples of the
dma_burst_len, and
+ * the dma_burst_len should be one of 8,7...2, otherwise, it will
be split
+ * into several SPI bursts by this driver
Fine, but then also rephrase the previous paragraph since you're
adding DMA.
Will do.
Could you precise on which platform you tested the DMA ?
aq222(S4)
Will you be able to test on other platforms ?
I tested it on other platforms over the last few days. G12A and C3 and
T7(T7 CLOCK use local source).
My board SPI does not connect peripherals and is tested through a
hardware loop.
I can test it on GXL and SM1 in the next two weeks against a SPI
display and some WS2812B LCDs.
Would be great, thx !
Neil
cmd:
spi_test -D /dev/spidev0.0 -v -s 5000000 -b 64 -l
*/
<snip>