-----Original Message-----
From: BOUGH CHEN
Sent: 2020年3月26日 12:41
To: Ulf Hansson <redacted>; Greg Kroah-Hartman
[off-list ref]; Rafael J . Wysocki [off-list ref];
linux-kernel@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>; Christoph Hellwig <hch@lst.de>;
Russell King [off-list ref]; Linus Walleij [off-list ref];
Vinod Koul [off-list ref]; Ludovic Barre [off-list ref];
linux-arm-kernel@lists.infradead.org; dmaengine@vger.kernel.org
Subject: RE: [PATCH 0/2] amba/platform: Initialize dma_parms at the bus level

quoted

-----Original Message-----
From: Ulf Hansson <redacted>
Sent: 2020年3月25日 19:34
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>; Rafael J .
Wysocki [off-list ref]; linux-kernel@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>; Christoph Hellwig <hch@lst.de>;
Russell King [off-list ref]; Linus Walleij
[off-list ref]; Vinod Koul [off-list ref]; BOUGH CHEN
[off-list ref]; Ludovic Barre [off-list ref];
linux-arm-kernel@lists.infradead.org; dmaengine@vger.kernel.org; Ulf
Hansson [off-list ref]
Subject: [PATCH 0/2] amba/platform: Initialize dma_parms at the bus
level

It's currently the amba/platform driver's responsibility to initialize
the pointer, dma_parms, for its corresponding struct device. The
benefit with this approach allows us to avoid the initialization and
to not waste memory for the struct device_dma_parameters, as this can
be decided on a case by case basis.

However, it has turned out that this approach is not very practical.
Not only does it lead to open coding, but also to real errors. In
principle callers of
dma_set_max_seg_size() doesn't check the error code, but just assumes
it succeeds.

For these reasons, this series initializes the dma_parms from the
amba/platform bus at the device registration point. This also follows
the way the PCI devices are being managed, see pci_device_add().

If it turns out that this is an acceptable solution, we probably also
want the changes for stable, but I am not sure if it applies without conflicts.

The series is based on v5.6-rc7.

Hi Ulf,

Since i.MXQM SMMU related code still not upstream yet, so I apply your
patches on our internal Linux branch based on v5.4.24, and find it do not work
on my side. Maybe for platform core drivers, there is a gap between v5.4.24
and v5.6-rc7 which has the impact.
I will try to put our SMMU related code into v5.6-rc7, then do the test again.

Hi Ulf,

On the latest Linux-next branch, the top commit 89295c59c1f063b533d071ca49d0fa0c0783ca6f (tag: next-20200326), after add your two patches, I just add the simple debug code as following in the /driver/mmc/core/queue.c, but seems still not work as our expect, logically, it should work, so can you or anyone test on other platform? This seems weird.

diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
index 25bee3daf9e2..f091280f7ffb 100644
--- a/drivers/mmc/core/queue.c
+++ b/drivers/mmc/core/queue.c

@@ -403,6 +403,13 @@ static void mmc_setup_queue(struct mmc_queue *mq, struct mmc_card *card)
                blk_queue_max_segment_size(mq->queue,
                        round_down(host->max_seg_size, block_size));

+       pr_err("###### the max segment size is %d\n", queue_max_segment_size(mq->queue));
+       if (host->parent->dma_parms) {
+                      pr_err("######### the dma parms has value\n");
+       } else if (!(host->parent->dma_parms)) {
+                      pr_err("######## the dma parms is zero!!\n");
+       }
+
        dma_set_max_seg_size(mmc_dev(host), queue_max_segment_size(mq->queue));

        INIT_WORK(&mq->recovery_work, mmc_mq_recovery_handler);

Here is the log I got when system run, even after your patch, the dev->dma_parms is still NULL. 
[    0.989853] mmc0: new HS400 MMC card at address 0001
[    0.995708] sdhci-esdhc-imx 30b50000.mmc: Got CD GPIO
[    0.999374] ###### the max segment size is 65024
[    1.008594] ######## the dma parms is zero!!
[    1.012875] mmcblk0: mmc0:0001 IB2932 29.2 GiB
[    1.017569] ###### the max segment size is 65024
[    1.022195] ######## the dma parms is zero!!
[    1.026479] mmcblk0boot0: mmc0:0001 IB2932 partition 1 4.00 MiB
[    1.032541] ###### the max segment size is 65024
[    1.035198] mmc1: SDHCI controller on 30b50000.mmc [30b50000.mmc] using ADMA
[    1.037169] ######## the dma parms is zero!!
[    1.048493] mmcblk0boot1: mmc0:0001 IB2932 partition 2 4.00 MiB
[    1.054531] mmcblk0rpmb: mmc0:0001 IB2932 partition 3 4.00 MiB, chardev (234:0)


Regards
Haibo Chen

Best Regards
Haibo Chen

quoted

Kind regards
Ulf Hansson

Ulf Hansson (2):
  driver core: platform: Initialize dma_parms for platform devices
  amba: Initialize dma_parms for amba devices

 drivers/amba/bus.c              | 2 ++
 drivers/base/platform.c         | 1 +
 include/linux/amba/bus.h        | 1 +
 include/linux/platform_device.h | 1 +
 4 files changed, 5 insertions(+)

--
2.20.1

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