linux-kernel - Re: [ v3 2/3] mtd: rawnand: stm32_fmc2: add STM32 FMC2 NAND flash controller driver

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Date:   Fri, 7 Dec 2018 11:18:08 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Christophe Kerello <christophe.kerello@...com>
Cc:     <boris.brezillon@...tlin.com>, <richard@....at>,
        <dwmw2@...radead.org>, <computersforpeace@...il.com>,
        <marek.vasut@...il.com>, <robh+dt@...nel.org>,
        <mark.rutland@....com>, <linux-mtd@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>
Subject: Re: [ v3 2/3] mtd: rawnand: stm32_fmc2: add STM32 FMC2 NAND flash
 controller driver

Hi Christophe,

Christophe Kerello <christophe.kerello@...com> wrote on Thu, 29 Nov
2018 17:41:02 +0100:

> The driver adds the support for the STMicroelectronics FMC2 NAND
> Controller found on STM32MP SOCs.
> 
> This patch is based on FMC2 command sequencer.
> The purpose of the command sequencer is to facilitate the programming
> and the reading of NAND flash pages with the ECC and to free the CPU
> of sequencing tasks.
> It requires one DMA channel for write and two DMA channels for read
> operations.
> 
> Only NAND_ECC_HW mode is actually supported.
> The driver supports a maximum 8k page size.
> The following ECC strength and step size are currently supported:
>  - nand-ecc-strength = <8>, nand-ecc-step-size = <512> (BCH8)
>  - nand-ecc-strength = <4>, nand-ecc-step-size = <512> (BCH4)
>  - nand-ecc-strength = <1>, nand-ecc-step-size = <512> (Extended ECC
>    based on Hamming)
> 
> This patch has been tested on Micron MT29F8G08ABACAH4 and
> MT29F8G16ABACAH4
> 
> Signed-off-by: Christophe Kerello <christophe.kerello@...com>
> ---

The driver look's good to me. However, Boris contributed new
cleanups that I would like you to take into account before doing
another 'deep' review. Please rebase on top of nand/next and have
a look at the followingcommits. For the ->select_chip() hook, it
should not be exposed anymore and switches should be handled
locally by the driver (you have examples).

7a08dbaedd36 mtd: rawnand: Move ->setup_data_interface() to nand_controller_ops
f2abfeb2078b mtd: rawnand: Move the ->exec_op() method to nand_controller_ops
7d6c37e90cf9 mtd: rawnand: Deprecate the ->select_chip() hook
1770022ffa85 mtd: rawnand: ams-delta: Stop implementing ->select_chip()
653c57c7da08 mtd: rawnand: vf610: Stop implementing ->select_chip()
2ace451cae22 mtd: rawnand: tegra: Stop implementing ->select_chip()
b25251414f6e mtd: rawnand: marvell: Stop implementing ->select_chip()
550b9fc4e3af mtd: rawnand: fsmc: Stop implementing ->select_chip()
02b4a52604a4 mtd: rawnand: Make ->select_chip() optional when ->exec_op() is implemented
ae2294b10b0f mtd: rawnand: Pass the CS line to be selected in struct nand_operation
1d0178593d14 mtd: rawnand: Add nand_[de]select_target() helpers

While at it, could you also address Linus W. comments.

Thanks,
Miquèl