[PATCH v2] mtd: rawnand: brcmnand: Initial exec_op implementation
William Zhang
william.zhang at broadcom.com
Thu Oct 5 17:42:21 PDT 2023
Hi Miquel,
On 10/03/2023 09:47 PM, William Zhang wrote:
>
>
> On 10/03/2023 03:55 PM, Miquel Raynal wrote:
>> Hi William,
>>
>> william.zhang at broadcom.com wrote on Tue, 3 Oct 2023 11:46:25 -0700:
>>
>>> Hi Miquel,
>>>
>>> On 10/03/2023 02:28 AM, Miquel Raynal wrote:
>>>> Hi William,
>>>>
>>>> william.zhang at broadcom.com wrote on Mon, 2 Oct 2023 12:57:01 -0700:
>>>>> Hi Miquel,
>>>>>
>>>>> On 10/02/2023 05:35 AM, Miquel Raynal wrote:
>>>>>> Hi David,
>>>>>>
>>>>>> dregan at mail.com wrote on Sat, 30 Sep 2023 03:57:35 +0200:
>>>>>> >>>> Initial exec_op implementation for Broadcom STB,
>>>>>> Broadband and iProc SoC
>>>>>>> This adds exec_op and removes the legacy interface.
>>>>>>>
>>>>>>> Signed-off-by: David Regan <dregan at mail.com>
>>>>>>> Reviewed-by: William Zhang <william.zhang at broadcom.com>
>>>>>>>
>>>>>>> ---
>>>>>>> >>>
>>>>>> ...
>>>>>> >>>> +static int brcmnand_parser_exec_matched_op(struct
>>>>>> nand_chip *chip,
>>>>>>> + const struct nand_subop *subop)
>>>>>>> +{
>>>>>>> + struct brcmnand_host *host = nand_get_controller_data(chip);
>>>>>>> + struct brcmnand_controller *ctrl = host->ctrl;
>>>>>>> + struct mtd_info *mtd = nand_to_mtd(chip);
>>>>>>> + const struct nand_op_instr *instr = &subop->instrs[0];
>>>>>>> + unsigned int i;
>>>>>>> + int ret = 0;
>>>>>>> +
>>>>>>> + for (i = 0; i < subop->ninstrs; i++) {
>>>>>>> + instr = &subop->instrs[i];
>>>>>>> +
>>>>>>> + if ((instr->type == NAND_OP_CMD_INSTR) &&
>>>>>>> + (instr->ctx.cmd.opcode == NAND_CMD_STATUS))
>>>>>>> + ctrl->status_cmd = 1;
>>>>>>> + else if (ctrl->status_cmd && (instr->type ==
>>>>>>> NAND_OP_DATA_IN_INSTR)) {
>>>>>>> + /*
>>>>>>> + * need to fake the nand device write protect
>>>>>>> because nand_base does a
>>>>>>> + * nand_check_wp which calls nand_status_op
>>>>>>> NAND_CMD_STATUS which checks
>>>>>>> + * that the nand is not write protected before an
>>>>>>> operation starts.
>>>>>>> + * The problem with this is it's done outside
>>>>>>> exec_op so the nand is
>>>>>>> + * write protected and this check will fail until
>>>>>>> the write or erase
>>>>>>> + * or write back operation actually happens where we
>>>>>>> turn off wp.
>>>>>>> + */
>>>>>>> + u8 *in;
>>>>>>> +
>>>>>>> + ctrl->status_cmd = 0;
>>>>>>> +
>>>>>>> + instr = &subop->instrs[i];
>>>>>>> + in = instr->ctx.data.buf.in;
>>>>>>> + in[0] = brcmnand_status(host) | NAND_STATUS_WP; /*
>>>>>>> hide WP status */
>>>>>>
>>>>>> I don't understand why you are faking the WP bit. If it's set,
>>>>>> brcmnand_status() should return it and you should not care about
>>>>>> it. If
>>>>>> it's not however, can you please give me the path used when we have
>>>>>> this issue? Either we need to modify the core or we need to provide
>>>>>> additional helpers in this driver to circumvent the faulty path.
>>>>>
>>>>> The reason we have to hide wp status for status command is because
>>>>> nand_base calls nand_check_wp at the very beginning of write and erase
>>>>> function. This applies to both exec_op path and legacy path. With
>>>>> Broadcom nand controller and most of our board design using the WP pin
>>>>> and have it asserted by default, the nand_check_wp function will fail
>>>>> and write/erase aborts. This workaround has been there before this
>>>>> exec_op patch.
>>>>>
>>>>> I agree it is ugly and better to be addressed in the nand base
>>>>> code. And
>>>>> I understand Broadcom's WP approach may sound a bit over cautious
>>>>> but we
>>>>> want to make sure no spurious erase/write can happen under any
>>>>> circumstance except software explicitly want to write and erase.
>>>>> WP is
>>>>> standard nand chip pin and I think most the nand controller has that
>>>>> that pin in the design too but it is possible it is not used and
>>>>> bootloader can de-assert the pin and have a always-writable nand flash
>>>>> for linux. So maybe we can add nand controller dts option
>>>>> "nand-use-wp".
>>>>> If this property exist and set to 1, wp control is in use and nand
>>>>> driver need to control the pin on/ff as needed when doing write and
>>>>> erase function. Also nand base code should not call nand_check_wp when
>>>>> wp is in use. Then we can remove the faking WP status workaround.
>>>>>> >>>> + } else if (instr->type == NAND_OP_WAITRDY_INSTR) {
>>>>>>> + ret = bcmnand_ctrl_poll_status(host, NAND_CTRL_RDY,
>>>>>>> NAND_CTRL_RDY, 0);
>>>>>>> + if (ctrl->wp_cmd) {
>>>>>>> + ctrl->wp_cmd = 0;
>>>>>>> + brcmnand_wp(mtd, 1);
>>>>>>
>>>>>> This ideally should disappear.
>>>>>> >> Maybe we can have the destructive operation patch from Borris.
>>>>> Controller driver still need to assert/deassert the pin if it uses
>>>>> nand
>>>>> wp feature but at least it does not need to guess the op code.
>>>>
>>>> Ah, yeah, I get it.
>>>>
>>>> Please be my guest, you can revive this patch series (might need light
>>>> tweaking, nothing big) and also take inspiration from it if necessary:
>>>> https://github.com/bbrezillon/linux/commit/e612e1f2c69a33ac5f2c91d13669f0f172d58717
>>>>
>>>> https://github.com/bbrezillon/linux/commit/4ec6f8d8d83f5aaca5d1877f02d48da96d41fcba
>>>>
>>>> https://github.com/bbrezillon/linux/commit/11b4acffd761c4928652d7028d19fcd6f45e4696
>>>>
>>> Sure we will incorporate the destructive operation patch and provide a
>>> new revision.
>>>
>>> The WP status workaround will stay at least for this change. If you
>>> think my suggestion using a dts setting above is okay, we can provide a
>>> patch for that as well. Or if you have any other idea or suggestion,
>>> we'd like to hear too.
>>
>> I thought this was not needed as Boris initial conversion did not need
>> it. The goal is to get rid of this workaround.
>> Boris' initial patch did remove that workaround but it will break the
> board that uses WP pin because the nand_check_wp run before the exec_op
> and status returned is write-protected in the erase and write function.
> I explained that above and you can see the code here:
> https://elixir.bootlin.com/linux/v6.6-rc4/source/drivers/mtd/nand/raw/nand_base.c#L4599
>
>
> I agree with your goal to remove this workaround and we have suggested
> one possible fix but we are also open to any other solution.
>
We have integrated the destructive operation patch and are ready for the
v3. If you don't think my proposal on the WP status fix is a good idea,
can we get this exce_op conversion patch series going first? After all,
we don't modify the WP status handling behavior in this patch. We can
fix it in another patch whenever we agree on a solution. Please let me
know and thanks a lot for all your comments and thoughts.
Thanks,
William
>
>> Thanks,
>> Miquèl
>>
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