[PATCH 00/16] mtd: spi-nor: aspeed: AST2600 support and extensions
Cédric Le Goater
clg at kaod.org
Fri Oct 11 20:29:49 AEDT 2019
On 11/10/2019 08:45, Boris Brezillon wrote:
> On Thu, 10 Oct 2019 23:47:45 +0000
> Joel Stanley <joel at jms.id.au> wrote:
>
>> On Wed, 9 Oct 2019 at 20:56, Boris Brezillon
>> <boris.brezillon at collabora.com> wrote:
>>>
>>> Hi Cedric,
>>>
>>> On Fri, 4 Oct 2019 13:59:03 +0200
>>> Cédric Le Goater <clg at kaod.org> wrote:
>>>
>>>> Hello,
>>>>
>>>> This series first extends the support for the Aspeed AST2500 and
>>>> AST2400 SMC driver. It adds Dual Data support and read training giving
>>>> the best read settings for a given chip. Support for the new AST2600
>>>> SoC is added at the end.
>>>>
>>>> I understand that a new spi_mem framework exists and I do have an
>>>> experimental driver using it. But unfortunately, it is difficult to
>>>> integrate the read training. The Aspeed constraints are not compatible
>>>> and i haven't had the time to extend the current framework.
>>>
>>> Hm, I don't think that's a good reason to push new features to the
>>> existing driver, especially since I asked others to migrate their
>>> drivers to spi-mem in the past. I do understand your concerns, and I'll
>>> let the SPI NOR/MTD maintainers make the final call, but I think it'd
>>> be better for the SPI MEM ecosystem to think about this link-training
>>> API (Vignesh needs it for the Cadence driver IIRC) rather than pushing
>>> this kind of feature to spi-nor controller drivers.
>>
>> As Cedric mentioned, the OpenBMC project has been shipping the read
>> training code for the ast2400/ast2400 for several years now. It would
>> be great to see it in mainline.
>>
>> I think it's reasonable to ask for the driver to be moved to the
>> spi-mem subsystem once it has the required APIs.
>
> Except it won't have the necessary APIs unless someone works on it, and
> adding this feature to existing spi-nor drivers won't help achieving
> this goal.
What would you suggest ? Something like the patch below which would
call a 'train' operation at the end of spi_add_device().
Also, when doing read training, we might need to know some lowlevel
characteristics of the chip being trained. Should we offer a way
to grab the probed m25p80 device and give access to the underlying
'struct spi_nor' ?
static struct spi_nor *spi_get_pnor(struct spi_device *spi)
{
struct spi_mem *spimem = spi_get_drvdata(spi);
struct m25p *flash = spi_mem_get_drvdata(spimem);
return flash ? &flash->spi_nor : NULL;
}
Yeah, it's hideous. I just want to raise the issue.
Thanks,
C.
>From b34297e6b991ff051bc1e16103d14b2a05c81827 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= <clg at kaod.org>
Date: Fri, 11 Oct 2019 11:09:33 +0200
Subject: [PATCH] spi: core: Add a device link training operation
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Signed-off-by: Cédric Le Goater <clg at kaod.org>
---
include/linux/spi/spi.h | 4 ++++
drivers/spi/spi.c | 23 +++++++++++++++++++++++
2 files changed, 27 insertions(+)
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index af4f265d0f67..950b39304807 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -409,6 +409,7 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv)
* @fw_translate_cs: If the boot firmware uses different numbering scheme
* what Linux expects, this optional hook can be used to translate
* between the two.
+ * @train : perform device link training
*
* Each SPI controller can communicate with one or more @spi_device
* children. These make a small bus, sharing MOSI, MISO and SCK signals
@@ -604,6 +605,9 @@ struct spi_controller {
void *dummy_tx;
int (*fw_translate_cs)(struct spi_controller *ctlr, unsigned cs);
+
+ int (*train)(struct spi_device *spi);
+
};
static inline void *spi_controller_get_devdata(struct spi_controller *ctlr)
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 75ac046cae52..759a66d74822 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -542,6 +542,22 @@ static int spi_dev_check(struct device *dev, void *data)
return 0;
}
+/**
+ * spi_train - link training of SPI device
+ * @spi: the device whose being trained
+ *
+ * Return: zero on success, else a negative error code.
+ */
+static int spi_train(struct spi_device *spi)
+{
+ int status = 0;
+
+ if (spi->controller->train)
+ status = spi->controller->train(spi);
+
+ return status;
+}
+
/**
* spi_add_device - Add spi_device allocated with spi_alloc_device
* @spi: spi_device to register
@@ -606,6 +622,13 @@ int spi_add_device(struct spi_device *spi)
else
dev_dbg(dev, "registered child %s\n", dev_name(&spi->dev));
+ status = spi_train(spi);
+ if (status < 0) {
+ dev_err(dev, "can't train %s, status %d\n",
+ dev_name(&spi->dev), status);
+ goto done;
+ }
+
done:
mutex_unlock(&spi_add_lock);
return status;
--
2.21.0
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