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arch/mips/pic32mz: fix the Ethernet D-Cache coherency.

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VIRT_ADDR() converted the DMA buffer addresses to KSEG1, while the
buffers come from g_buffers, which is linked in KSEG0 when the data
memory is cached.  Buffers then ended up in the free list under both
aliases.  Use the segment g_buffers is linked in instead.

A buffer handed to an RX descriptor may still have dirty D-Cache lines,
at least the free list link written into it.  If such a line is evicted
while the DMA writes the frame, it overwrites part of the frame.
Discard the buffer from the D-Cache before giving it to the DMA.

Assisted-by: Claude Code:claude-opus-5-5
Signed-off-by: Daniel P. Carvalho <danieloak@gmail.com>
This commit is contained in:
Daniel P. Carvalho 2026-10-04 00:54:54 -03:00 • committed by Alan C. Assis
parent 74eafb0354
commit 8eae6d950d
1 changed files with 38 additions and 3 deletions
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41
arch/mips/src/pic32mz/pic32mz_ethernet.c
View file

@ -334,7 +334,11 @@
/* Misc Helper Macros *******************************************************/
#define PHYS_ADDR(va) ((uint32_t)(va) & 0x1fffffff)
#define VIRT_ADDR(pa) (KSEG1_BASE | (uint32_t)(pa))
/* Buffers are always accessed through the segment g_buffers is linked in
* (KSEG0 or KSEG1), so that no buffer is ever reached through two aliases.
*/
#define VIRT_ADDR(pa) (((uint32_t)g_buffers & 0xe0000000) | (uint32_t)(pa))
/****************************************************************************
* Private Types
@ -445,6 +449,7 @@ static void pic32mz_dumprxdesc(struct pic32mz_rxdesc_s *rxdesc,
static inline void pic32mz_bufferinit(struct pic32mz_driver_s *priv);
static uint8_t *pic32mz_allocbuffer(struct pic32mz_driver_s *priv);
static uint8_t *pic32mz_rxbuffer(struct pic32mz_driver_s *priv);
static void pic32mz_freebuffer(struct pic32mz_driver_s *priv,
uint8_t *buffer);
@ -768,6 +773,36 @@ static uint8_t *pic32mz_allocbuffer(struct pic32mz_driver_s *priv)
return (uint8_t *)sq_remfirst(&priv->pd_freebuffers);
}
/****************************************************************************
* Function: pic32mz_rxbuffer
*
* Description:
* Allocate one buffer for an RX descriptor. The free list link and any
* data left by the network stack may still sit in dirty D-Cache lines;
* they are discarded so that a later eviction cannot overwrite the frame
* written by the DMA.
*
* Input Parameters:
* priv - Pointer to EMAC device driver structure
*
* Returned Value:
* Pointer to the allocated buffer (or NULL on failure)
*
****************************************************************************/
static uint8_t *pic32mz_rxbuffer(struct pic32mz_driver_s *priv)
{
uint8_t *buffer = pic32mz_allocbuffer(priv);
if (buffer != NULL)
{
up_invalidate_dcache((uintptr_t)buffer,
(uintptr_t)buffer + PIC32MZ_ALIGNED_BUFSIZE);
}
return buffer;
}
/****************************************************************************
* Function: pic32mz_freebuffer
*
@ -905,7 +940,7 @@ static inline void pic32mz_rxdescinit(struct pic32mz_driver_s *priv)
rxdesc->rsv1 = 0;
rxdesc->rsv2 = 0;
rxdesc->address = PHYS_ADDR(pic32mz_allocbuffer(priv));
rxdesc->address = PHYS_ADDR(pic32mz_rxbuffer(priv));
rxdesc->status = RXDESC_STATUS_EOWN | RXDESC_STATUS_NPV;
/* Set the NEXTED pointer. If this is the last descriptor in the
@ -1514,7 +1549,7 @@ static void pic32mz_rxdone(struct pic32mz_driver_s *priv)
* descriptor back to the hardware with its current buffer.
*/
rxbuffer = pic32mz_allocbuffer(priv);
rxbuffer = pic32mz_rxbuffer(priv);
if (rxbuffer == NULL)
{
nwarn("WARNING: No free buffer, packet dropped\n");