From: Boris Brezillon <boris.brezillon@bootlin.com>
To: naga suresh kumar <nagasureshkumarrelli@gmail.com>
Cc: nagasure@xilinx.com, cyrille.pitchen@wedev4u.fr,
"Marek Vašut" <marek.vasut@gmail.com>,
"David Woodhouse" <dwmw2@infradead.org>,
"Brian Norris" <computersforpeace@gmail.com>,
boris.brezillon@free-electrons.com,
linux-mtd@lists.infradead.org
Subject: Re: [RFC PATCH 0/5] RFC for Zynq QSPI
Date: Tue, 18 Sep 2018 09:17:12 +0200 [thread overview]
Message-ID: <20180918091712.2f97db80@bbrezillon> (raw)
In-Reply-To: <CALgLF9JVweEcEm6L33HaHp4HtXhmsZL7J5FDe8+O11i0Q1nukg@mail.gmail.com>
Hi Naga,
On Tue, 18 Sep 2018 11:26:05 +0530
naga suresh kumar <nagasureshkumarrelli@gmail.com> wrote:
> Hi,
>
> Please see my reply inline by prefacing my name, currently i am facing
> issues with my outlook. the reply looks not good but please don't mind.
I do mind. Please find a way to fix that, 'cause I'm pretty sure others
will soon complain about that too.
> > > As i said, it needs tweaking the mtd->size and spi read/write addresses.
> >
> > Can you elaborate a bit on why you think this is needed? Did you look
> > at [1]? Maybe it will prevent us from exposing the flash size at the
> > spi-mem level.
> > [naga]: some example snippet below
> >
> > spi_nor_read () {
> >
> > if (nor->isparallel == 1)
> >
> > {
> >
> > offset /= 2; //byte stripping will happen here
> >
> > nor->spi->master->flags |= SPI_DATA_STRIPE;
> >
> > //By setting this flag even bits of data word located in lower
> > memory and odd are in upper memory
> >
> > }
> >
> > if (nor->isstacked == 1) {
> >
> > stack_shift = 1;
> >
> > if (offset >= (mtd->size / 2)) {
> >
> > offset = offset - (mtd->size / 2);
> >
> > nor->spi->master->flags |= SPI_MASTER_U_PAGE;
> >
> > //We can access Upper memory or lower memory, by setting this flag in
> > controller.
> >
> > } else {
> >
> > nor->spi->master->flags &= ~SPI_MASTER_U_PAGE;
> >
> > }
> >
> > }
> >
> > same for spi_nor_write() also.
Let's put the stacked and parallel support on the side for now and
focus on single die/chip support. Will find a clean way to handle that
afterwards.
> >
> > Also in both dual parallel and stacked mode mtd->size should be sum of
> > both flash device sizes
Yes, but this information should stay at the spi-nor/mtd level.
> >
> > also status register read will change, it needs status from both devices.
> > like that some changes
> >
> > will be needed in core.
Which is why this needs to be handled in spi-nor.c. The spi-nor core
needs to know about the parallel/stack setup and handle it differently
(read both status bytes, read both IDs, ...).
> > > Can somebody share your thoughts on this(Adding Zynq QSPI Dual parallel
> > and
> > > stacked)?
> >
> > I always have a hard time with this naming. I guess stacked is when you
> > have 2 chips sharing the same I/O bus, and parallel is when you have 2
> > chips with one taking all of the I/O and the other taking the other
> > half. Is that correct?
> > [naga]: Yes, you are correct, i have attached the diagrams for these mode.
> >
> > In parallel mode, with the help of controller STRIPE feature, even bits of
> >
> > data words are located in lower memory and odd bits are located in upper
> > memory.
> >
> > Data management will be taken care by controller in both modes
Ok. I need to think about it a bit more. In the meantime, I recommend
that you submit a version of the driver that does not support parallel
and stacked modes.
Regards,
Boris
next prev parent reply other threads:[~2018-09-18 7:17 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-23 12:21 [RFC PATCH 0/5] RFC for Zynq QSPI Naga Sureshkumar Relli
2018-03-23 12:21 ` [RFC PATCH 1/5] spi: Add support for Zynq qspi controller Naga Sureshkumar Relli
2018-03-23 12:21 ` [RFC PATCH 2/5] mtd: spi-nor: Add support for Zynq QSPI controller Naga Sureshkumar Relli
2018-03-23 12:22 ` [RFC PATCH 3/5] mtd: spi-nor: Add Dual Parallel and Stacked support for Zynq QSPI Naga Sureshkumar Relli
2018-03-23 12:22 ` [RFC PATCH 4/5] spi: Add PM Support for Zynq QSPI controller Naga Sureshkumar Relli
2018-03-23 12:22 ` [RFC PATCH 5/5] devicetree: Add devicetree bindings documentation for Naga Sureshkumar Relli
2018-03-23 14:47 ` Miquel Raynal
2018-03-23 12:52 ` [RFC PATCH 0/5] RFC for Zynq QSPI Marek Vasut
2018-03-23 13:39 ` Naga Sureshkumar Relli
2018-04-16 7:25 ` Naga Sureshkumar Relli
[not found] ` <CALgLF9K=rZxVx_QXvV_LH3OhidTcguZ=K=p=Lf9AfFbk4H+8Zw@mail.gmail.com>
2018-09-17 15:05 ` Boris Brezillon
2018-09-17 15:07 ` Boris Brezillon
[not found] ` <CALgLF9JVweEcEm6L33HaHp4HtXhmsZL7J5FDe8+O11i0Q1nukg@mail.gmail.com>
2018-09-18 7:17 ` Boris Brezillon [this message]
2018-09-18 8:58 ` Naga Sureshkumar Relli
2019-06-26 9:53 ` naga suresh kumar
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