20402106a3
As usual these patches were extracted and rebased from the raspberry pi repo: https://github.com/raspberrypi/linux/tree/rpi-4.4.y Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
115 lines
3.7 KiB
Diff
115 lines
3.7 KiB
Diff
From 930015dce415e4203daeafb09c24759ac883613e Mon Sep 17 00:00:00 2001
|
|
From: Martin Sperl <kernel@martin.sperl.org>
|
|
Date: Wed, 16 Mar 2016 12:25:00 -0700
|
|
Subject: [PATCH 398/423] dmaengine: bcm2835: limit max length based on channel
|
|
type
|
|
|
|
The bcm2835 dma system has 2 basic types of dma-channels:
|
|
* "normal" channels
|
|
* "light" channels
|
|
|
|
Lite channels are limited in several aspects:
|
|
* internal data-structure is 128 bit (not 256)
|
|
* does not support BCM2835_DMA_TDMODE (2D)
|
|
* DMA length register is limited to 16 bit.
|
|
so 0-65535 (not 0-65536 as mentioned in the official datasheet)
|
|
* BCM2835_DMA_S/D_IGNORE are not supported
|
|
|
|
The detection of the type of mode is implemented by looking at
|
|
the LITE bit in the DEBUG register for each channel.
|
|
This allows automatic detection.
|
|
|
|
Based on this the maximum block size is set to (64K - 4) or to 1G
|
|
and this limit is honored during generation of control block
|
|
chains. The effect is that when a LITE channel is used more
|
|
control blocks are used to do the same transfer (compared
|
|
to a normal channel).
|
|
|
|
As there are several sources/target DREQS that are 32 bit wide
|
|
we need to have the transfer to be a multiple of 4 as this would
|
|
break the transfer otherwise.
|
|
|
|
This is why the limit of (64K - 4) was chosen over the
|
|
alternative of (64K - 4K).
|
|
|
|
Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
|
|
Reviewed-by: Eric Anholt <eric@anholt.net>
|
|
Signed-off-by: Eric Anholt <eric@anholt.net>
|
|
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
|
|
---
|
|
drivers/dma/bcm2835-dma.c | 29 ++++++++++++++++++++++++++---
|
|
1 file changed, 26 insertions(+), 3 deletions(-)
|
|
|
|
--- a/drivers/dma/bcm2835-dma.c
|
|
+++ b/drivers/dma/bcm2835-dma.c
|
|
@@ -81,6 +81,8 @@ struct bcm2835_chan {
|
|
|
|
void __iomem *chan_base;
|
|
int irq_number;
|
|
+
|
|
+ bool is_lite_channel;
|
|
};
|
|
|
|
struct bcm2835_desc {
|
|
@@ -169,6 +171,16 @@ struct bcm2835_desc {
|
|
#define BCM2835_DMA_CHAN(n) ((n) << 8) /* Base address */
|
|
#define BCM2835_DMA_CHANIO(base, n) ((base) + BCM2835_DMA_CHAN(n))
|
|
|
|
+/* the max dma length for different channels */
|
|
+#define MAX_DMA_LEN SZ_1G
|
|
+#define MAX_LITE_DMA_LEN (SZ_64K - 4)
|
|
+
|
|
+static inline size_t bcm2835_dma_max_frame_length(struct bcm2835_chan *c)
|
|
+{
|
|
+ /* lite and normal channels have different max frame length */
|
|
+ return c->is_lite_channel ? MAX_LITE_DMA_LEN : MAX_DMA_LEN;
|
|
+}
|
|
+
|
|
/* how many frames of max_len size do we need to transfer len bytes */
|
|
static inline size_t bcm2835_dma_frames_for_length(size_t len,
|
|
size_t max_len)
|
|
@@ -217,8 +229,10 @@ static void bcm2835_dma_create_cb_set_le
|
|
size_t *total_len,
|
|
u32 finalextrainfo)
|
|
{
|
|
- /* set the length */
|
|
- control_block->length = len;
|
|
+ size_t max_len = bcm2835_dma_max_frame_length(chan);
|
|
+
|
|
+ /* set the length taking lite-channel limitations into account */
|
|
+ control_block->length = min_t(u32, len, max_len);
|
|
|
|
/* finished if we have no period_length */
|
|
if (!period_len)
|
|
@@ -544,6 +558,7 @@ static struct dma_async_tx_descriptor *b
|
|
dma_addr_t src, dst;
|
|
u32 info = BCM2835_DMA_WAIT_RESP;
|
|
u32 extra = BCM2835_DMA_INT_EN;
|
|
+ size_t max_len = bcm2835_dma_max_frame_length(c);
|
|
size_t frames;
|
|
|
|
/* Grab configuration */
|
|
@@ -586,7 +601,10 @@ static struct dma_async_tx_descriptor *b
|
|
}
|
|
|
|
/* calculate number of frames */
|
|
- frames = DIV_ROUND_UP(buf_len, period_len);
|
|
+ frames = /* number of periods */
|
|
+ DIV_ROUND_UP(buf_len, period_len) *
|
|
+ /* number of frames per period */
|
|
+ bcm2835_dma_frames_for_length(period_len, max_len);
|
|
|
|
/*
|
|
* allocate the CB chain
|
|
@@ -685,6 +703,11 @@ static int bcm2835_dma_chan_init(struct
|
|
c->ch = chan_id;
|
|
c->irq_number = irq;
|
|
|
|
+ /* check in DEBUG register if this is a LITE channel */
|
|
+ if (readl(c->chan_base + BCM2835_DMA_DEBUG) &
|
|
+ BCM2835_DMA_DEBUG_LITE)
|
|
+ c->is_lite_channel = true;
|
|
+
|
|
return 0;
|
|
}
|
|
|