netdev - Re: [PATCH V5 1/3] can: flexcan: initialize all flexcan memory for ECC function

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Date:   Tue, 29 Sep 2020 15:21:18 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Joakim Zhang <qiangqing.zhang@....com>, linux-can@...r.kernel.org
Cc:     netdev@...r.kernel.org, linux-imx@....com
Subject: Re: [PATCH V5 1/3] can: flexcan: initialize all flexcan memory for
 ECC function

On 9/29/20 11:15 PM, Joakim Zhang wrote:
> One issue was reported at a baremetal environment, which is used for
> FPGA verification. "The first transfer will fail for extended ID
> format(for both 2.0B and FD format), following frames can be transmitted
> and received successfully for extended format, and standard format don't
> have this issue. This issue occurred randomly with high possiblity, when
> it occurs, the transmitter will detect a BIT1 error, the receiver a CRC
> error. According to the spec, a non-correctable error may cause this
> transfer failure."
> 
> With FLEXCAN_QUIRK_DISABLE_MECR quirk, it supports correctable errors,
> disable non-correctable errors interrupt and freeze mode. Platform has
> ECC hardware support, but select this quirk, this issue may not come to
> light. Initialize all FlexCAN memory before accessing them, at least it
> can avoid non-correctable errors detected due to memory uninitialized.
> The internal region can't be initialized when the hardware doesn't support
> ECC.
> 
> According to IMX8MPRM, Rev.C, 04/2020. There is a NOTE at the section
> 11.8.3.13 Detection and correction of memory errors:
> "All FlexCAN memory must be initialized before starting its operation in
> order to have the parity bits in memory properly updated. CTRL2[WRMFRZ]
> grants write access to all memory positions that require initialization,
> ranging from 0x080 to 0xADF and from 0xF28 to 0xFFF when the CAN FD feature
> is enabled. The RXMGMASK, RX14MASK, RX15MASK, and RXFGMASK registers need to
> be initialized as well. MCR[RFEN] must not be set during memory initialization."
> 
> Memory range from 0x080 to 0xADF, there are reserved memory (unimplemented
> by hardware, e.g. only configure 64 MBs), these memory can be initialized or not.
> In this patch, initialize all flexcan memory which includes reserved memory.
> 
> In this patch, create FLEXCAN_QUIRK_SUPPORT_ECC for platforms which has ECC
> feature. If you have a ECC platform in your hand, please select this
> qurik to initialize all flexcan memory firstly, then you can select
> FLEXCAN_QUIRK_DISABLE_MECR to only enable correctable errors.
> 
> Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
> ---
> ChangeLogs:
> V1->V2:
> 	* update commit messages, add a datasheet reference.
> 	* initialize block memory instead of trivial memory.
> 	* inilialize reserved memory.
> V2->V3:
> 	* add FLEXCAN_QUIRK_SUPPORT_ECC quirk.
> 	* remove init_ram struct.
> V3->V4:
> 	* move register definition into flexcan_reg.
> V4->V5:
> 	* use offsetof instead of cast

looks good now. Should I try to get this into v5.10?

Marc
-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |



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