On Fri, 6 Nov 2020 08:58:23 +0000 Chin-Ting Kuo <chin-ting_...@aspeedtech.com> wrote:
> Hi Boris, > > Thanks for your quick reply. > > > -----Original Message----- > > From: Boris Brezillon <boris.brezil...@collabora.com> > > Sent: Thursday, November 5, 2020 11:12 PM > > To: Cédric Le Goater <c...@kaod.org>; robh...@kernel.org > > Cc: Chin-Ting Kuo <chin-ting_...@aspeedtech.com>; broo...@kernel.org; > > j...@jms.id.au; and...@aj.id.au; bbrezil...@kernel.org; > > devicet...@vger.kernel.org; linux-kernel@vger.kernel.org; > > linux-asp...@lists.ozlabs.org; linux-...@vger.kernel.org; BMC-SW > > <bmc...@aspeedtech.com> > > Subject: Re: [v3 4/4] spi: aspeed: Add ASPEED FMC/SPI memory controller > > driver > > > > Hi, > > > > On Thu, 5 Nov 2020 15:09:11 +0100 > > Cédric Le Goater <c...@kaod.org> wrote: > > > > > Hello Chin-Ting, > > > > > > Thanks for this driver. It's much cleaner than the previous and we > > > should try adding support for the AST2500 SoC also. I guess we can > > > keep the old driver for the AST2400 which has a different register layout. > > > > > > On the patchset, I think we should split this patch in three : > > > > > > - basic support > > > - AHB window calculation depending on the flash size > > > - read training support > > > > I didn't look closely at the implementation, but if the read training tries > > to read > > a section of the NOR, I'd recommend exposing that feature through spi-mem > > and letting the SPI-NOR framework trigger the training instead of doing > > that at > > dirmap creation time (remember that spi-mem is also used for SPI NANDs > > which use the dirmap API too, and this training is unlikely to work there). > > > > The SPI-NOR framework could pass a read op template and a reference pattern > > such that all the spi-mem driver has to do is execute the template op and > > compare the output to the reference buffer. > > > > I agree it. Before, I were not able to find a suitable location to implement > read training feature. > I think that I can add a SPI timing training function in > "spi_controller_mem_ops" struct and > call it by a wrapper function called at the bottom of spi_nor_probe() in > spi-nor.c. > Maybe, SPI-NOR framework does not need to pass reference buffer since > calibration > method depends on each SoC itself and buffer size may be variant. > The detail calibration method may be implemented in each SoC SPI driver. That's a real problem IMO. What makes this pattern SoC specific? I can see why the location in flash could be *board* specific, but the pattern should be pretty common, right? As for the spi-mem operation to be executed, it's definitely memory specific (I can imagine some flash vendors providing a specific command returning a fixed pattern that's not actually stored on a visible portion of the flash). > > Besides, I am thinking about the possibility for adding a "spi_mem_post_init" > function in > spi-mem framework sine for some SoCs, SPI controller needs to adjust some > settings > after getting SPI flash information. I don't think that's a good idea. The spi-mem interface should stay memory-type agnostic and doing that means we somehow pass NOR specific info. What is it that you need exactly, and why?
