From: Simon Horman <simon.horman@corigine.com>
To: Markus Schneider-Pargmann <msp@baylibre.com>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>,
Chandrasekar Ramakrishnan <rcsekar@samsung.com>,
Wolfgang Grandegger <wg@grandegger.com>,
Vincent MAILHOL <mailhol.vincent@wanadoo.fr>,
linux-can@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 08/18] can: m_can: Write transmit header and data in one transaction
Date: Thu, 26 Jan 2023 09:04:56 +0100 [thread overview]
Message-ID: <Y9I0KEeWq0JFy6iB@corigine.com> (raw)
In-Reply-To: <20230125195059.630377-9-msp@baylibre.com>
On Wed, Jan 25, 2023 at 08:50:49PM +0100, Markus Schneider-Pargmann wrote:
> Combine header and data before writing to the transmit fifo to reduce
> the overhead for peripheral chips.
>
> Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> ---
> drivers/net/can/m_can/m_can.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
> index 78f6ed744c36..440bc0536951 100644
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -1681,6 +1681,7 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
> m_can_write(cdev, M_CAN_TXBAR, 0x1);
> /* End of xmit function for version 3.0.x */
> } else {
> + char buf[TXB_ELEMENT_SIZE];
> /* Transmit routine for version >= v3.1.x */
>
> txfqs = m_can_read(cdev, M_CAN_TXFQS);
> @@ -1720,12 +1721,11 @@ static netdev_tx_t m_can_tx_handler(struct m_can_classdev *cdev)
> fifo_header.dlc = FIELD_PREP(TX_BUF_MM_MASK, putidx) |
> FIELD_PREP(TX_BUF_DLC_MASK, can_fd_len2dlc(cf->len)) |
> fdflags | TX_BUF_EFC;
> - err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_ID, &fifo_header, 2);
> - if (err)
> - goto out_fail;
> + memcpy(buf, &fifo_header, 8);
> + memcpy(&buf[8], &cf->data, cf->len);
>
> - err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_DATA,
> - cf->data, DIV_ROUND_UP(cf->len, 4));
> + err = m_can_fifo_write(cdev, putidx, M_CAN_FIFO_ID,
> + buf, 8 + DIV_ROUND_UP(cf->len, 4));
Perhaps I am missing something here, but my reading is that:
- 8 is a length in bytes
- the 5th argument to m_can_fifo_write is the val_count parameter,
whose unit is 4-byte long values.
By this logic, perhaps the correct value for this argument is:
DIV_ROUND_UP(8 + cf->len, 4)
Also:
- If cf->len is not a multiple of 4, is there a possibility
that uninitialised trailing data in buf will be used
indirectly by m_can_fifo_write()?
> if (err)
> goto out_fail;
>
> --
> 2.39.0
>
next prev parent reply other threads:[~2023-01-26 8:05 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-25 19:50 [PATCH v2 00/18] can: m_can: Optimizations for m_can/tcan part 2 Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 01/18] can: tcan4x5x: Remove reserved register 0x814 from writable table Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 02/18] can: tcan4x5x: Check size of mram configuration Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 03/18] can: m_can: Remove repeated check for is_peripheral Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 04/18] can: m_can: Always acknowledge all interrupts Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 05/18] can: m_can: Remove double interrupt enable Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 06/18] can: m_can: Disable unused interrupts Markus Schneider-Pargmann
2023-01-26 8:07 ` Simon Horman
2023-01-25 19:50 ` [PATCH v2 07/18] can: m_can: Keep interrupts enabled during peripheral read Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 08/18] can: m_can: Write transmit header and data in one transaction Markus Schneider-Pargmann
2023-01-26 8:04 ` Simon Horman [this message]
2023-01-30 8:04 ` Markus Schneider-Pargmann
2023-02-04 13:05 ` Simon Horman
2023-02-20 5:31 ` Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 09/18] can: m_can: Implement receive coalescing Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 10/18] can: m_can: Implement transmit coalescing Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 11/18] can: m_can: Add rx coalescing ethtool support Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 12/18] can: m_can: Add tx " Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 13/18] can: m_can: Cache tx putidx Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 14/18] can: m_can: Use the workqueue as queue Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 15/18] can: m_can: Introduce a tx_fifo_in_flight counter Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 16/18] can: m_can: Use tx_fifo_in_flight for netif_queue control Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 17/18] can: m_can: Implement BQL Markus Schneider-Pargmann
2023-01-25 19:50 ` [PATCH v2 18/18] can: m_can: Implement transmit submission coalescing Markus Schneider-Pargmann
2023-01-28 15:00 ` Vincent MAILHOL
2023-01-30 8:05 ` Markus Schneider-Pargmann
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