[PATCH v2 1/2] mtd: rawnand: qcom: Fix clock sequencing in qcom_nandc_probe()

[Greg KH]

On Thu, Jan 06, 2022 at 05:24:27PM +0000, Bryan O'Donoghue wrote:
> On 03/01/2022 05:51, Manivannan Sadhasivam wrote:
> > On Mon, Jan 03, 2022 at 03:03:15AM +0000, Bryan O'Donoghue wrote:
> > > Interacting with a NAND chip on an IPQ6018 I found that the qcomsmem NAND
> > > partition parser was returning -EPROBE_DEFER waiting for the main smem
> > > driver to load.
> > > 
> > > This caused the board to reset. Playing about with the probe() function
> > > shows that the problem lies in the core clock being switched off before the
> > > nandc_unalloc() routine has completed.
> > > 
> > > If we look at how qcom_nandc_remove() tears down allocated resources we see
> > > the expected order is
> > > 
> > > qcom_nandc_unalloc(nandc);
> > > 
> > > clk_disable_unprepare(nandc->aon_clk);
> > > clk_disable_unprepare(nandc->core_clk);
> > > 
> > > dma_unmap_resource(&pdev->dev, nandc->base_dma, resource_size(res),
> > > 		   DMA_BIDIRECTIONAL, 0);
> > > 
> > > Tweaking probe() to both bring up and tear-down in that order removes the
> > > reset if we end up deferring elsewhere.
> > > 
> > > Fixes: c76b78d8ec05 ("mtd: nand: Qualcomm NAND controller driver")
> > > Signed-off-by: Bryan O'Donoghue <bryan.odonoghue at linaro.org>
> > 
> > Reviewed-by: Manivannan Sadhasivam <mani at kernel.org>
> > 
> > Can you please CC stable list for backporting?
> > 
> > Thanks,
> > Mani
> > 
> 
> NP.
> 
> + cc stable
> 
> FWIW I believe Greg's scripts will pick up on Fixes: tags automatically

No, that is NOT the way to ensure that a patch will get picked up, that
is a "this might eventually get there".

Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

thanks,

greg k-h