diff mbox series

[net-next,09/20] can: rockchip_canfd: rkcanfd_handle_rx_int_one(): implement workaround for erratum 5: check for empty FIFO

Message ID 20240904094218.1925386-10-mkl@pengutronix.de (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series [net-next,01/20] dt-bindings: can: rockchip_canfd: add rockchip CAN-FD controller | expand

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Context Check Description
netdev/series_format warning Pull request is its own cover letter; Series longer than 15 patches (PR)
netdev/tree_selection success Clearly marked for net-next, async
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 16 this patch: 16
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers warning 5 maintainers not CCed: pabeni@redhat.com mailhol.vincent@wanadoo.fr edumazet@google.com linux-arm-kernel@lists.infradead.org linux-rockchip@lists.infradead.org
netdev/build_clang success Errors and warnings before: 16 this patch: 16
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 16 this patch: 16
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 54 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline fail Was 0 now: 1

Commit Message

Marc Kleine-Budde Sept. 4, 2024, 9:38 a.m. UTC 
The rk3568 CAN-FD errata sheet as of Tue 07 Nov 2023 11:25:31 +08:00
says:

| Erratum 5: Counters related to the TXFIFO and RXFIFO exhibit
| abnormal counting behavior.
|
| Due to a bug in the cross-asynchronous logic of the enable signals
| for rx_fifo_cnt and txe_fifo_frame_cnt counters, the counts of these
| two counters become inaccurate. This issue has resulted in the
| inability to use the TXFIFO and RXFIFO functions.

The errata sheet mentioned above states that only the rk3568v2 is
affected by this erratum, but tests with the rk3568v2 and rk3568v3
show that the RX_FIFO_CNT is sometimes too high. This leads to CAN
frames being read from the FIFO, which is then already empty.

Further tests on the rk3568v2 and rk3568v3 show that in this
situation (i.e. empty FIFO) all elements of the FIFO
header (frameinfo, id, ts) contain the same data.

On the rk3568v2 and rk3568v3, this problem only occurs extremely
rarely with the standard clock of 300 MHz, but almost immediately at
80 MHz.

To workaround this problem, check for empty FIFO with
rkcanfd_fifo_header_empty() in rkcanfd_handle_rx_int_one() and exit
early.

Tested-by: Alibek Omarov <a1ba.omarov@gmail.com>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patch.msgid.link/20240904-rockchip-canfd-v5-9-8ae22bcb27cc@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/net/can/rockchip/rockchip_canfd-rx.c | 14 +++++++++++++
 drivers/net/can/rockchip/rockchip_canfd.h    | 22 ++++++++++++++++++++
 2 files changed, 36 insertions(+)
diff mbox series

Patch

diff --git a/drivers/net/can/rockchip/rockchip_canfd-rx.c b/drivers/net/can/rockchip/rockchip_canfd-rx.c
index 5398aff0d180..609282359bca 100644
--- a/drivers/net/can/rockchip/rockchip_canfd-rx.c
+++ b/drivers/net/can/rockchip/rockchip_canfd-rx.c
@@ -47,6 +47,16 @@  rkcanfd_fifo_header_to_cfd_header(const struct rkcanfd_priv *priv,
 	return len + cfd->len;
 }
 
+static inline bool
+rkcanfd_fifo_header_empty(const struct rkcanfd_fifo_header *header)
+{
+	/* Erratum 5: If the FIFO is empty, we read the same value for
+	 * all elements.
+	 */
+	return header->frameinfo == header->id &&
+		header->frameinfo == header->ts;
+}
+
 static int rkcanfd_handle_rx_int_one(struct rkcanfd_priv *priv)
 {
 	struct net_device_stats *stats = &priv->ndev->stats;
@@ -63,6 +73,10 @@  static int rkcanfd_handle_rx_int_one(struct rkcanfd_priv *priv)
 	rkcanfd_read_rep(priv, RKCANFD_REG_RX_FIFO_RDATA,
 			 cfd->data, sizeof(cfd->data));
 
+	/* Erratum 5: Counters for TXEFIFO and RXFIFO may be wrong */
+	if (rkcanfd_fifo_header_empty(header))
+		return 0;
+
 	len = rkcanfd_fifo_header_to_cfd_header(priv, header, cfd);
 
 	/* Drop any received CAN-FD frames if CAN-FD mode is not
diff --git a/drivers/net/can/rockchip/rockchip_canfd.h b/drivers/net/can/rockchip/rockchip_canfd.h
index 3dafb5e68dc5..c775e75a2740 100644
--- a/drivers/net/can/rockchip/rockchip_canfd.h
+++ b/drivers/net/can/rockchip/rockchip_canfd.h
@@ -315,6 +315,28 @@ 
 
 /* Erratum 5: Counters related to the TXFIFO and RXFIFO exhibit
  * abnormal counting behavior.
+ *
+ * The rk3568 CAN-FD errata sheet as of Tue 07 Nov 2023 11:25:31 +08:00
+ * states that only the rk3568v2 is affected by this erratum, but
+ * tests with the rk3568v2 and rk3568v3 show that the RX_FIFO_CNT is
+ * sometimes too high. This leads to CAN frames being read from the
+ * FIFO, which is then already empty.
+ *
+ * Further tests on the rk3568v2 and rk3568v3 show that in this
+ * situation (i.e. empty FIFO) all elements of the FIFO header
+ * (frameinfo, id, ts) contain the same data.
+ *
+ * On the rk3568v2 and rk3568v3, this problem only occurs extremely
+ * rarely with the standard clock of 300 MHz, but almost immediately
+ * at 80 MHz.
+ *
+ * To workaround this problem, check for empty FIFO with
+ * rkcanfd_fifo_header_empty() in rkcanfd_handle_rx_int_one() and exit
+ * early.
+ *
+ * To reproduce:
+ * assigned-clocks = <&cru CLK_CANx>;
+ * assigned-clock-rates = <80000000>;
  */
 #define RKCANFD_QUIRK_RK3568_ERRATUM_5 BIT(4)